Arquivo da tag: Genética

Ancient viral molecules essential for human development (Science Daily)

26/11/2015UncategorizedEvolução, Genética, Haraway, Infecção, Microbiologia, Vírusrenzotaddei

Date: November 23, 2015

Source: Stanford University Medical Center

Summary: Genetic material from ancient viral infections is critical to human development, according to researchers.

Rendering of a virus among blood cells. Credit: © ysfylmz / Fotolia

Genetic material from ancient viral infections is critical to human development, according to researchers at the Stanford University School of Medicine.

They’ve identified several noncoding RNA molecules of viral origins that are necessary for a fertilized human egg to acquire the ability in early development to become all the cells and tissues of the body. Blocking the production of this RNA molecule stops development in its tracks, they found.

The discovery comes on the heels of a Stanford study earlier this year showing that early human embryos are packed full of what appear to be viral particles arising from similar left-behind genetic material.

“We’re starting to accumulate evidence that these viral sequences, which originally may have threatened the survival of our species, were co-opted by our genomes for their own benefit,” said Vittorio Sebastiano, PhD, an assistant professor of obstetrics and gynecology. “In this manner, they may even have contributed species-specific characteristics and fundamental cell processes, even in humans.”

Sebastiano is a co-lead and co-senior author of the study, which will be published online Nov. 23 in Nature Genetics. Postdoctoral scholar Jens Durruthy-Durruthy, PhD, is the other lead author. The other senior author of the paper is Renee Reijo Pera, PhD, a former professor of obstetrics and gynecology at Stanford who is now on the faculty of Montana State University.

Sebastiano and his colleagues were interested in learning how cells become pluripotent, or able to become any tissue in the body. A human egg becomes pluripotent after fertilization, for example. And scientists have learned how to induce other, fully developed human cells to become pluripotent by exposing them to proteins known to be present in the very early human embryo. But the nitty-gritty molecular details of this transformative process are not well understood in either case.

An ancient infection

The researchers knew that a type of RNA molecules called long-intergenic noncoding, or lincRNAs, have been implicated in many important biological processes, including the acquisition of pluripotency. These molecules are made from DNA in the genome, but they don’t go on to make proteins. Instead they function as RNA molecules to affect the expression of other genes.

Sebastiano and Durruthy-Durruthy used recently developed RNA sequencing techniques to examine which lincRNAs are highly expressed in human embryonic stem cells. Previously, this type of analysis was stymied by the fact that many of the molecules contain highly similar, very repetitive regions that are difficult to sequence accurately.

They identified more than 2,000 previously unknown RNA sequences, and found that 146 are specifically expressed in embryonic stem cells. They homed in on the 23 most highly expressed sequences, which they termed HPAT1-23, for further study. Thirteen of these, they found, were made up almost entirely of genetic material left behind after an eons-ago infection by a virus called HERV-H.

HERV-H is what’s known as a retrovirus. These viruses spread by inserting their genetic material into the genome of an infected cell. In this way, the virus can use the cell’s protein-making machinery to generate viral proteins for assembly into a new viral particle. That particle then goes on to infect other cells. If the infected cell is a sperm or an egg, the retroviral sequence can also be passed to future generations.

HIV is one common retrovirus that currently causes disease in humans. But our genomes are also littered with sequences left behind from long-ago retroviral infections. Unlike HIV, which can go on to infect new cells, these retroviral sequences are thought to be relatively inert; millions of years of evolution and accumulated mutations mean that few maintain the capacity to give instructions for functional proteins.

After identifying HPAT1-23 in embryonic stem cells, Sebastiano and his colleagues studied their expression in human blastocysts — the hollow clump of cells that arises from the egg in the first days after fertilization. They found that HPAT2, HPAT3 and HPAT5 were expressed only in the inner cell mass of the blastocyst, which becomes the developing fetus. Blocking their expression in one cell of a two-celled embryo stopped the affected cell from contributing to the embryo’s inner cell mass. Further studies showed that the expression of the three genes is also required for efficient reprogramming of adult cells into induced pluripotent stem cells.

Sequences found only in primates

“This is the first time that these virally derived RNA molecules have been shown to be directly involved with and necessary for vital steps of human development,” Sebastiano said. “What’s really interesting is that these sequences are found only in primates, raising the possibility that their function may have contributed to unique characteristics that distinguish humans from other animals.”

The researchers are continuing their studies of all the HPAT molecules. They’ve learned that HPAT-5 specifically affects pluripotency by interacting with and sequestering members of another family of RNAs involved in pluripotency called let-7.

“Previously retroviral elements were considered to be a class that all functioned in basically the same way,” said Durruthy-Durruthy. “Now we’re learning that they function as individual elements with very specific and important roles in our cells. It’s fascinating to imagine how, during the course of evolution, primates began to recycle these viral leftovers into something that’s beneficial and necessary to our development.”

Journal Reference:

Jens Durruthy-Durruthy, Vittorio Sebastiano, Mark Wossidlo, Diana Cepeda, Jun Cui, Edward J Grow, Jonathan Davila, Moritz Mall, Wing H Wong, Joanna Wysocka, Kin Fai Au, Renee A Reijo Pera. The primate-specific noncoding RNA HPAT5 regulates pluripotency during human preimplantation development and nuclear reprogramming. Nature Genetics, 2015; DOI: 10.1038/ng.3449

‘Não podemos brincar de Deus com as alterações no genoma humano’, alerta ONU (ONU)

08/10/2015UncategorizedÉtica, Biotecnologias, ciência, Engenharia genética, Genética, Incerteza, Riscorenzotaddei

Publicado em 07/10/2015. Atualizado em 07/10/2015

A modificação do código genético permite tratar doenças como o câncer, mas pode gerar mudanças hereditárias. UNESCO pede uma regulamentação clara sobre os procedimentos científicos e informação à população.

“Terapia genética poderia ser o divisor de águas na história da medicina e a alteração no genoma é sem dúvida um dos maiores empreendimentos da ciência em nome da humanidade”, afirmou a Organização das Nações Unidas para a Educação, a Ciência e a Cultura (UNESCO) sobre um relatório publicado pelo Comitê Internacional de Bioética (IBC) nesta segunda-feira (5).

O IBC acrescentou, no entanto, que intervenções no genoma humano deveriam ser autorizadas somente em casos preventivos, diagnósticos ou terapêuticos que não gerem alterações para os descendentes. O relatório destaca também a importância da regulamentação e informação clara aos consumidores.

O documento ressaltou os avanços na possibilidade de testes genéticos em casos de doenças hereditárias, por meio da terapia genética, o uso de células tronco embrionárias na pesquisa médica e uso de clones e alterações genéticas para fins medicinais. São citadas também novas técnicas que podem inserir, tirar e corrigir o DNA, podendo tratar ou curar o câncer e outras doenças. Porém, estas mesmas técnicas também possibilitam mudanças no DNA, como determinar a cor dos olhos de um bebê, por exemplo.

“O grande medo é que podemos estar tentando “brincar de Deus” com consequências imprevisíveis” e no final precipitando a nossa própria destruição”, alertou o antigo secretário-geral da ONU, Kofi Annan em 2004, quando perguntado qual seria a linha ética que determinaria o limite das alterações no genoma humano. Para responder a essa questão, os Estados-membros da UNESCO adotaram em 2005 a Declaração Universal sobre Bioética e Direitos Humanos que lida com os dilemas éticos levantados pelas rápidas mudanças na medicina, na ciência e tecnologia.

SBPC critica projeto sobre biodiversidade (Fapesp)

23/02/2015UncategorizedÍndios, Biodiversidade, Capitalismo, ciência, Genéticarenzotaddei

Texto aprovado na Câmara dos Deputados facilita o acesso ao patrimônio genético e conhecimentos associados, mas ignora os direitos das comunidades indígenas e tradicionais, diz presidente da entidade

BRUNO DE PIERRO | Edição Online 11:00 20 de fevereiro de 2015

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A Sociedade Brasileira para o Progresso da Ciência (SBPC), que representa 120 associações científicas, divulgou esta semana uma carta em que sugere modificações no projeto de lei sobre biodiversidade e recursos genéticos, aprovado na Câmara dos Deputados no dia 10 de fevereiro e que será agora apreciado pelo Senado. No documento, a entidade critica a prerrogativa do Estado de ignorar direitos de comunidades indígenas e tradicionais na repartição de benefícios resultantes do acesso ao conhecimento associado ao patrimônio genético. Prevista no Protocolo de Nagoya, assinado por 91 países – entre eles o Brasil – a repartição de benefícios envolve o compromisso de compensar financeiramente países e comunidades pelo uso de seus recursos genéticos e conhecimentos tradicionais. O protocolo foi aprovado pela 10^aConferência das Partes em 2010, e ainda não foi ratificado pelo Congresso brasileiro.

Outro aspecto destacado na carta é que a repartição dos benefícios só será aplicada sobre a comercialização de produtos acabados, que chegarão ao mercado. “Isso fere o direito do povo e da comunidade de participar da tomada de decisão quanto à repartição de benefícios oriundos do acesso ao conhecimento tradicional associado”, escreve no documento Helena Nader, professora titular da Universidade Federal de São Paulo (Unifesp) e presidente da SBPC. Também é questionado um tópico da lei que permite a instituições estrangeiras acessarem a biodiversidade brasileira, para fins de pesquisa e desenvolvimento, sem precisar se associar a uma instituição nacional, como estabelece a legislação vigente. Na carta, a SBPC reconhece avanços no projeto aprovado, entre eles a retirada da necessidade de autorização prévia para a realização de pesquisas com recursos genéticos.

Em junho do ano passado, o governo federal enviou para o Congresso Nacional o PL 7.735, em caráter de urgência. O projeto simplifica o acesso e exploração do patrimônio genético em pesquisas com plantas e animais nativos e facilita a utilização de conhecimentos tradicionais e indígenas associados à biodiversidade. Um dos principais avanços da proposta é que o acesso aos recursos genéticos para fins de pesquisa e desenvolvimento tecnológico dependerá apenas de um cadastro eletrônico e não mais de uma solicitação a órgãos como o Conselho de Gestão do Patrimônio Genético (CGen), do Ministério do Meio Ambiente (MMA), e o Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). A medida atende a um pleito antigo da comunidade científica e de setores industriais, que nos últimos tempos levaram adiante seus estudos sem seguir a legislação à risca e foram multados.

No entanto, após a votação na Câmara, a comunidade científica, representada pela SBPC, criticou alguns pontos da lei. “O projeto de lei reconhece o direito de populações indígenas, comunidades tradicionais e pequenos agricultores de participar da tomada de decisões, mas isenta, em muitos casos, as empresas e pesquisadores da obrigação de repartir os benefícios, que é a compensação econômica do detentor do conhecimento tradicional associado à biodiversidade”, explica Helena Nader.

O projeto aprovado estabelece que o pagamento desses benefícios à comunidade que detém o conhecimento associado seja estabelecido em um Acordo de Repartição de Benefícios, no qual esteja a definição do montante negociado a título de repartição de benefícios. O usuário também deverá depositar no Fundo Nacional de Repartição de Benefícios (FNRB) 0,5% da receita líquida anual obtida por meio da exploração do material reprodutivo, como sementes ou sêmen, decorrentes do acesso ao conhecimento tradicional para beneficiar os codetentores do mesmo conhecimento.

Se a exploração envolver algum componente do patrimônio genético, a repartição monetária de benefícios será de 1% da receita líquida anual das vendas do produto acabado ou material reprodutivo, a ser depositada no FNRB. Há ainda a previsão de se estabelecer um acordo setorial, no qual a repartição de benefícios poderá ser reduzida até de 0,1% da receita líquida da comercialização do produto acabado ou material reprodutivo. É dada a possibilidade da repartição não ser feita em dinheiro, mas sim por transferência de tecnologia e outras formas de cooperação entre as partes envolvidas, como o intercâmbio de recursos humanos e materiais entre instituições nacionais e participação na pesquisa. Em algumas situações, no entanto, é impossível identificar a origem do conhecimento, que já está difundido na sociedade. Nesses casos, o pagamento de royalties será destinado ao FNRB, para, entre outras coisas, proteger a biodiversidade e os conhecimentos tradicionais.

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Contudo, diz Helena Nader, a lei exclui da obrigação de repartir benefícios os fabricantes de produtos intermediários e desenvolvedores de processos oriundos de acesso ao patrimônio genético ou ao conhecimento tradicional associado ao longo da cadeia produtiva. Também isenta micro e pequenas empresas do dever de dividir os benefícios com as comunidades tradicionais. “Não é justo, nem ético, definir quando se dará a repartição de benefícios oriunda do acesso a conhecimentos tradicionais associados, sem antes consultar os detentores de tais conhecimentos”, diz ela.

Para Vanderlan Bolzani, professora da Universidade Estadual Paulista (Unesp) e membro da coordenação do programa Biota-FAPESP, a nova legislação falha ao não exigir que a compensação econômica seja revertida em benefícios sociais para a comunidade local. “Muitas dessas populações vivem em situação precária e dependem unicamente do extrativismo como fonte de sobrevivência. Além do pagamento de royalties, são necessárias ações que promovam o desenvolvimento social e econômico dessas comunidades”, diz Vanderlan.

Entidades representantes das populações extrativistas e indígenas alegam que não foram convidadas para participar de reuniões com representantes do governo e da indústria. De acordo com o deputado federal Alceu Moreira (PMDB-RS), relator do projeto, as reuniões que antecederam a votação no Congresso contaram com a participação de membros da Fundação Nacional do Índio (Funai) e do Instituto Nacional de Colonização e Reforma Agrária (Incra), que segundo ele representam oficialmente os índios e outras comunidades tradicionais. “Não fizemos uma assembleia geral aberta por se tratar de um tema muito técnico”, disse Moreira.

Para o biólogo Braulio Ferreira de Souza Dias, secretário-executivo da Convenção sobre Diversidade Biológica (CDB) da Organização das Nações Unidas (ONU), o Congresso Nacional deveria aproveitar o debate em torno da nova lei e considerar a ratificação do Protocolo de Nagoya, em vigor desde outubro do ano passado. “Trata-se do principal instrumento internacional sobre acesso a recursos genéticos”, afirma Dias. Segundo ele, o projeto aprovado na Câmara fere o Protocolo de Nagoya no que se refere ao direito do país provedor de recursos genéticos e conhecimentos tradicionais de receber repartição dos benefícios. Isso porque, segundo um artigo do projeto aprovado na Câmara, a utilização do patrimônio genético de espécies introduzidas no país pela ação humana até a data de entrada em vigor da lei não estará sujeita à repartição de benefícios prevista em acordos internacionais dos quais o Brasil seja parte. “Isso poderá criar embaraços ao acesso a recursos genéticos e conhecimentos tradicionais de outros países necessários para o aprimoramento da agricultura brasileira, inclusive para promover sua adaptação às mudanças climáticas”, diz Dias.

Facilitação para estrangeiros
Hoje, para o pesquisador estrangeiro ou pessoa jurídica estrangeira vir ao Brasil realizar pesquisa que envolva coleta de dados, materiais, espécimes biológicas e minerais, peças integrantes da cultura nativa e cultura popular, o Ministério da Ciência, Tecnologia e Inovação (MCTI) deve autorizar, supervisionar a fiscalização e analisar os resultados obtidos. Somente são autorizadas as atividades em que haja a coparticipação de alguma instituição de pesquisa brasileira bem avaliada pelo CNPq. A nova proposta agora permite que entidades estrangeiras, não associadas a instituições nacionais, realizem pesquisa com a biodiversidade do país mediante uma autorização do CGen.

“Abriu-se a possibilidade da pessoa jurídica estrangeira ter autorização para acesso a componente do patrimônio genético do Brasil sem estar associada a uma instituição de ciência e tecnologia nacional, o que é preocupante”, diz Helena Nader. Isso, diz ela, pode ameaçar os interesses nacionais e colocar em risco o patrimônio brasileiro. Helena ressalta que, em outros países latino-americanos com biodiversidade muito rica, exige-se que instituições estrangeiras tenham vínculo com órgãos de pesquisa nacionais, de modo a proteger interesses do país provedor de recursos genéticos. “Se proibirmos que instituições de outros países venham pesquisar aqui, perderemos a oportunidade de desenvolver ciência de qualidade no país”, argumenta o deputado Alceu Moreira. Helena Nader afirma que não se trata de proibir a vinda de estrangeiros. “Trata-se apenas de manter a instituição internacional comprometida com os interesses da pesquisa brasileira. É uma forma de cooperação científica em que os dois lados ganham”, diz ela.

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Avanços
O CGen atualmente é composto por 19 representantes de órgãos e de entidades da administração pública federal. A partir de 2003, passou a contar com representantes da sociedade na função de membros convidados permanentes, com direito a voz mas não a voto. A primeira versão do PL 7.735 não garantia a participação plena de representantes da sociedade civil. Após negociações, o texto foi modificado e houve uma mudança na composição do CGen, com 60% de representantes do governo e 40% de membros da sociedade civil, entre eles representantes das comunidades indígenas e tradicionais, pesquisadores e agricultores tradicionais. “Esse foi um importante avanço obtido com a aprovação do projeto de lei. A comunidade científica e outros segmentos sociais demandam essa participação plena, com direito a voto, há muito tempo”, explica Helena Nader.

Outro avanço do projeto aprovado foi inserir em seu escopo os recursos genéticos para a alimentação e a agricultura. Antes, na proposta enviada pelo poder executivo, esses recursos estavam de fora e ficariam no âmbito da legislação antiga, de 2001. Segundo à nova proposta de lei, os royalties serão cobrados sobre a comercialização do material reprodutivo – a semente, por exemplo. Já a exploração econômica do produto acabado será isenta da compensação, com exceção das variedades cultivadas pelas comunidades tradicionais ou indígenas.

A não obrigação de se repartir os benefícios também vale para a pesquisa básica que, segundo Vanderlan Bolzani, se beneficiará da nova lei. “A ciência não acessa a biodiversidade apenas para dela retirar produtos. É importante estudar a estrutura molecular de plantas, por exemplo, para compreender como se desenvolve a vida em determinada região”, explica Vanderlan. Segundo ela, a maioria dos cientistas que pesquisam a biodiversidade está hoje na ilegalidade. Nos últimos anos, as punições para quem não segue a legislação se tornaram mais severas. Dados do governo federal, divulgados pela Agência Câmara, mostram que as ações de um núcleo de combate ao acesso ilegal ao patrimônio genético, que atuou em 2010, resultaram em multas com valor total de aproximadamente R$ 220 milhões.

Um dos casos mais notórios ocorreu em novembro daquele ano, com a autuação, em R$ 21 milhões, da empresa de cosméticos Natura por uso da biodiversidade sem autorização. A empresa, que mantem parceria com universidades para pesquisas novas moléculas, não esperou os trâmites para liberar a permissão do chamado provedor (seja o governo ou uma comunidade tradicional ou indígena) e um contrato de repartição de benefícios. A Natura alegou que todos os seus produtos têm repartição de benefícios, mas reclamou que não poderia esperar dois anos por uma autorização de pesquisa do CGen (ver Pesquisa FAPESP nº 179).

Huge epigenomic map examines life’s impact on our genes (New Scientist)

19/02/2015UncategorizedEpigenética, Genéticarenzotaddei

18 February 2015 by Catherine Brahic

Magazine issue 3009.

THE nature versus nurture debate is getting a facelift this week, with the publication of a genetic map that promises to tell us which bits of us are set in stone by our DNA, and which bits we can affect by how we live our lives.

The new “epigenomic” map doesn’t just look at genes, but also the instructions that govern them. Compiled by a consortium of biologists and computer scientists, this information will allow doctors to pinpoint precisely which cells in the body are responsible for various diseases. It might also reveal how to adjust your lifestyle to counter a genetic predisposition to a particular disease.

“The epigenome is the additional information our cells have on top of genetic information,” says lead researcher Manolis Kellis of the Massachusetts Institute of Technology. It is made of chemical tags that are attached to DNA and its packaging. These tags act like genetic controllers, influencing whether a gene is switched on or off, and play an instrumental role in shaping our bodies and disease.

Researchers are still figuring out exactly how and when epigenetic tags are added to our DNA, but the process appears to depend on environmental cues. We inherit some tags from our parents, but what a mother eats during pregnancy, for instance, might also change her baby’s epigenome. Others tags relate to the environment we are exposed to as children and adults. “The epigenome sits in a very special place between nature and nurture,” says Kellis.

Each cell type in our body has a different epigenome – in fact, the DNA tags are the reason why our cells come in such different shapes and sizes despite having exactly the same DNA. So for its map, the Roadmap Epigenomics Consortium collected thousands of cells from different adult and embryonic tissues, and meticulously analysed all the tags.

So far, they have produced 127 epigenomes, each corresponding to a different cell type, from brain cells to skin cells. That’s a big advance on the 16 published in 2012 by the ENCODE project, which are included in the new map.

The consortium also cross-referenced these healthy epigenomes with previous data on the genetic components of dozens of diseases, including type 1 diabetes, Crohn’s disease, high blood pressure, inflammatory bowel disease and Alzheimer’s disease (see “Alzheimer’s epigenetics“).

The results, says Kellis, allow doctors to see what cell types are likely to be disrupted in people with these conditions. For instance, they suggest disruptions in the epigenome of the brain’s cingulate gyrus cells may play a role in attention deficit hyperactivity disorder (Nature, DOI: 10.1038/nature14248).

Richard Meehan of the University of Edinburgh, UK, says the work offers “incredibly valuable information which will be absorbed and debated for years to come”. He suggests that one day doctors will look at your epigenomes during routine health checks to suss out how the nature versus nurture battle is playing out inside your cells. These scans would reveal your genetic predisposition to certain conditions, and how your lifestyle is affecting those risks.

By adjusting your choices accordingly, you will be able to delay disease, or minimise its effects for as long as possible. “It’s not going to move any further forward the point at which your life ends, but make the years up to that point – years that are spent in physical decline – a whole lot better,” says Meehan.

“You see this on Star Trek,” he adds. “Nobody lives any longer but they just seem to be healthier up to the point where life, unfortunately, passes away.”

Alzheimer’s epigenetics

While you can’t change the genes you were born with, you might be able to alter your epigenome – and its influence on your health – through tinkering with your lifestyle.

Studying cells from people with Alzheimer’s and a mouse version of the disease highlights both immune cells and brain cells as key players. This finding supports other studies suggesting that an immune disorder is at least partially responsible for Alzheimer’s.

Manolis Kellis and his team at MIT (see main story) were able to identify both genetic and non-genetic effects. While the immune disruptions were coded in the cells’ genetics, the changes in the brain cells appeared to be influenced by environmental inputs like diet, education, physical activity and age, and are probably associated with epigenetic changes (Nature, DOI: 10.1038/nature14252).

“We have an interplay between genetics and epigenetics,” says Kellis. “You might not be able to do anything about the genetic but you might be able to do something about the epigenomic by – I don’t know – maybe reading more books.”

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Cientistas publicam o primeiro atlas do epigenoma humano (O Globo)

Dados sobre processos que afetam células, responsáveis por sua diferenciação em 111 dos tecidos do corpo, podem ajudar na melhor compreensão de diversas doenças e no desenvolvimento de novos tratamentos para elas

POR CESAR BAIMA

19/02/2015 6:00 / ATUALIZADO 19/02/2015 8:38

No alvo: epigenoma abre caminho para novas abordagens no tratamento e cura de várias doenças
Foto: Alamy/Latinstock

No alvo: epigenoma abre caminho para novas abordagens no tratamento e cura de várias doenças – Alamy/Latinstock

RIO – Sequenciado completamente pela primeira vez há pouco mais de uma década, o genoma humano, com suas cerca de 3 bilhões de “letras”, guarda todas as informações necessárias para “construir” uma pessoa. Mas, apesar de quase todas nossas células terem o mesmo DNA, elas podem, e devem, ser muito diferentes umas das outras para que o corpo funcione bem. Afinal, os neurônios do cérebro cumprem trabalhos bem distintos do das células do músculo cardíaco, que por sua vez não poderiam fazer o que fazem as do fígado.

É a conhecida diferenciação celular, e para que isso aconteça é preciso controlar quais genes serão ativados e quais permanecerão dormentes nas células. E é aí que entra em cena o chamado epigenoma, nome dado ao conjunto de processos e reações químicas que regulam esta expressão genética. Ele teve seu primeiro atlas de ação em 111 tecidos que compõem o feto e o organismo humano publicado ontem na edição desta semana da revista “Nature”, junto com mais de 20 artigos neste e outros periódicos científicos abordando seus mecanismos e possíveis relações com doenças e condições como asma, câncer, problemas cardíacos e Alzheimer.

COMO PREENCHER UM ‘MAPA-MÚNDI’ EM BRANCO

Isso porque, mesmo não alterando diretamente o DNA, o epigenoma tem grande importância na maneira como nossas células funcionam e pode ser influenciado por fatores ambientais e hábitos individuais, como a poluição e o tabagismo. Em alguns casos, inclusive, sua atuação pode até mesmo ser hereditária, ajudando a responder o mistério do que é fruto da natureza e o que é resultado da criação — cuja resposta, muitas vezes, deverá ser “ambos”. Segundo os pesquisadores, é como se o genoma fosse um mapa-múndi em branco ao qual o estudo do epigenoma agora acrescenta os nomes dos países, estados e cidades, suas rodovias e ferrovias e a localização de portos e aeroportos, tornando-o muito mais útil.

— Hoje, podemos sequenciar o genoma humano de forma rápida e barata, mas interpretar este genoma ainda é um desafio — lembra Bing Ren, professor da Universidade da Califórnia em San Diego e coautor de diversos dos artigos relacionados ao projeto de mapeamento do epigenoma. — Estes 111 mapas de referência do epigenoma são essencialmente um livro de vocabulário que nos ajuda a decifrar cada segmento do DNA em células distintas e tipos de tecido. Estes mapas são como retratos do genoma humano em ação.

Diante disso, ainda durante o projeto — no qual o Instituto Nacional de Saúde dos EUA (NIH) investiu US$ 300 milhões desde 2006 numa colaboração de centenas de cientistas de dezenas de instituições espalhadas pelo mundo —, diversos pesquisadores começaram a buscar na interação entre genoma e epigenoma possíveis fatores que levam ao desenvolvimento de doenças, abrindo caminho para novas abordagens na busca de tratamentos ou cura.

— As células do fígado e do cérebro usam diferentes pedaços do DNA para produzir um repertório distinto de proteínas dependendo de como os marcadores epigenéticos foram introduzidos em cada célula durante o desenvolvimento embrionário — destaca Steven Jones, professor da Universidade Simon Fraser, no Canadá e outro dos participantes no projeto. — E estes marcadores podem mudar ao longo da vida em resposta a fatores ambientais. De fato, mudanças nos padrões epigenéticos originais de uma célula já foram associadas a diversas doenças humanas, incluindo câncer e Alzheimer.

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Epigenética na agricultura é tema de livro (Facesp)

11/02/2015UncategorizedAgronomia, Epigenética, Genética, Tomatesrenzotaddei

11 de fevereiro de 2015

Por Diego Freire

Agência FAPESP – Pesquisadores da Universidade de São Paulo (USP) estão entre os autores e editores do livro Epigenetics in Plants of Agronomic Importance: Fundamentals and Applications, publicado pela editora Springer, que trata do controle da expressão gênica de plantas de interesse agronômico, como o tomate.

Um dos editores é Juan Armando Casas-Mollano, que conduz no Instituto de Química (IQ) a pesquisa “Caracterização funcional de uma recentemente identificada família de MUT9 kinases in Arabidopsis thaliana e cana-de-açúcar”, com apoio da FAPESP na modalidade Jovem Pesquisador, no âmbito do Programa FAPESP de Pesquisa em Bioenergia (BIOEN).

“O livro reúne informações sobre plantas além das chamadas plantas modelo, como a Arabidopsis, amplamente utilizada em todas as áreas da ciência por ter um genoma pequeno e um ciclo de vida rápido e por ser de fácil manipulação”, disse Casas-Mollano.

A epigenética é o estudo de qualquer transformação na expressão de genes que ocorre sem haver mudança na sequência do DNA. Essas alterações, de ordem química, podem ocorrer na molécula de DNA e em proteínas chamadas histonas, podendo ser herdadas na divisão celular. O fenômeno tem alto impacto na biologia do organismo e na definição de diferentes fenótipos, isto é, da sua morfologia, do seu desenvolvimento e de aspectos do comportamento.

“O livro tem informações detalhadas sobre os mecanismos epigenéticos em plantas de importância agronômica. Essas informações podem trazer contribuições para o desenvolvimento de técnicas de manipulação, inibição ou ativação e seleção de proteínas e vias metabólicas, permitindo criar plantas resistentes a patógenos e a estresse ambiental, além de aumentar a produtividade”, afirmou Casas-Mollano.

O pesquisador é coautor do capítulo Histone H3 Phosphorylation in Plants and Other Organisms, com Izabel Moraes, também do IQ. O capítulo revisa e discute avanços mais recentes no estudo de fosforilação de proteínas histonas em plantas.

A fosforilação é a adição de um grupo fosfato a uma proteína ou a outra molécula, sendo um dos principais elementos nos mecanismos de regulação das proteínas, associada ao silenciamento gênico.

“Trata-se de ‘desligar’ a expressão de um gene por meio de mecanismos que não estejam relacionados à modificação de sua sequência gênica. Dessa forma, um gene que está sendo expresso, ou ‘ligado’, naturalmente é ‘desligado’, conforme a necessidade, por meio da fosforilação”, explicou Moraes.

A pesquisadora investiga no IQ o papel de determinados genes no controle do tempo de floração das plantas, fundamental para o sucesso da sua propagação, no projeto de pós-doutorado Compreendendo o papel das kinases MUT9 na regulação do tempo de floração em Arabidopsis thaliana, realizado com apoio da FAPESP e orientação de Casas-Mollano.

O livro conta ainda com um capítulo de autoria do também pesquisador da USP Fabio Tebaldi Silveira Nogueira, da Escola Superior de Agricultura Luiz de Queiroz (Esalq), que trata da epigenética do tomate. Nogueira conduz em Piracicaba a pesquisa Análise funcional do papel de microRNAs no controle da arquitetura vegetativa e desenvolvimento de frutos, com apoio da FAPESP.

Epigenetics in Plants of Agronomic Importance: Fundamentals and Applications – Transcriptional Regulation and Chromatin Remodelling in Plants
Editores: Raul Alvarez-Venegas, Clelia de la Peña, Juan Armando Casas-Mollano
Lançamento: 2014
Preço: US$ 149
Páginas: 152

Mais informações: www.springer.com/life+sciences/plant+sciences/book/978-3-319-07970-7

Do viruses make us smarter? (Science Daily)

13/01/2015UncategorizedEcologia, Epigenética, Genética, neurociências, Vírusrenzotaddei

Date: January 12, 2015

Source: Lund University

Summary: Inherited viruses that are millions of years old play an important role in building up the complex networks that characterize the human brain, researchers say. They have found that retroviruses seem to play a central role in the basic functions of the brain, more specifically in the regulation of which genes are to be expressed, and when.

Retroviruses seem to play a central role in the basic functions of the brain, more specifically in the regulation of which genes are to be expressed, and when, researchers say. Credit: © Sergey Bogdanov / Fotolia

A new study from Lund University in Sweden indicates that inherited viruses that are millions of years old play an important role in building up the complex networks that characterise the human brain.

Researchers have long been aware that endogenous retroviruses constitute around five per cent of our DNA. For many years, they were considered junk DNA of no real use, a side-effect of our evolutionary journey.

In the current study, Johan Jakobsson and his colleagues show that retroviruses seem to play a central role in the basic functions of the brain, more specifically in the regulation of which genes are to be expressed, and when. The findings indicate that, over the course of evolution, the viruses took an increasingly firm hold on the steering wheel in our cellular machinery. The reason the viruses are activated specifically in the brain is probably due to the fact that tumours cannot form in nerve cells, unlike in other tissues.

“We have been able to observe that these viruses are activated specifically in the brain cells and have an important regulatory role. We believe that the role of retroviruses can contribute to explaining why brain cells in particular are so dynamic and multifaceted in their function. It may also be the case that the viruses’ more or less complex functions in various species can help us to understand why we are so different,” says Johan Jakobsson, head of the research team for molecular neurogenetics at Lund University.

The article, based on studies of neural stem cells, shows that these cells use a particular molecular mechanism to control the activation processes of the retroviruses. The findings provide us with a complex insight into the innermost workings of the most basal functions of the nerve cells. At the same time, the results open up potential for new research paths concerning brain diseases linked to genetic factors.

“I believe that this can lead to new, exciting studies on the diseases of the brain. Currently, when we look for genetic factors linked to various diseases, we usually look for the genes we are familiar with, which make up a mere two per cent of the genome. Now we are opening up the possibility of looking at a much larger part of the genetic material which was previously considered unimportant. The image of the brain becomes more complex, but the area in which to search for errors linked to diseases with a genetic component, such as neurodegenerative diseases, psychiatric illness and brain tumours, also increases.”

Journal Reference:

Liana Fasching, Adamandia Kapopoulou, Rohit Sachdeva, Rebecca Petri, Marie E. Jönsson, Christian Männe, Priscilla Turelli, Patric Jern, Florence Cammas, Didier Trono, Johan Jakobsson. TRIM28 Represses Transcription of Endogenous Retroviruses in Neural Progenitor Cells. Cell Reports, 2015; 10 (1): 20 DOI: 10.1016/j.celrep.2014.12.004

Cientistas descobrem dois genes relacionados a crimes violentos (Zero Hora)

31/10/2014UncategorizedEvolucionismo, Genética, Sociobiologia, Violênciarenzotaddei

Jc, 5055, 30 de outubro de 2014

A característica estava presente em 10% dos 900 criminosos finlandeses analisados em estudo de instituto sueco

Mais um estudo científico conclui que a genética pode estar relacionada a crimes violentos. Desta vez, a partir da análise de quase 900 criminosos na Finlândia, pesquisadores descobriram dois genes que ampliaram em 13 vezes as chances de a pessoa ter comportamento violento repetidamente.

Veja a matéria completa em: http://zh.clicrbs.com.br/rs/noticias/planeta-ciencia/noticia/2014/10/cientistas-descobrem-dois-genes-relacionados-a-crimes-violentos-4630569.html

(Zero Hora)

How learning to talk is in the genes (Science Daily)

17/09/2014UncategorizedCognição, Genética, Linguagem, Linguística, neurociênciasrenzotaddei

Date: September 16, 2014

Source: University of Bristol

Summary: Researchers have found evidence that genetic factors may contribute to the development of language during infancy. Scientists discovered a significant link between genetic changes near the ROBO2 gene and the number of words spoken by children in the early stages of language development.

Researchers have found evidence that genetic factors may contribute to the development of language during infancy. Credit: © witthaya / Fotolia

Researchers have found evidence that genetic factors may contribute to the development of language during infancy.

Scientists from the Medical Research Council (MRC) Integrative Epidemiology Unit at the University of Bristol worked with colleagues around the world to discover a significant link between genetic changes near the ROBO2 gene and the number of words spoken by children in the early stages of language development.

Children produce words at about 10 to 15 months of age and our range of vocabulary expands as we grow — from around 50 words at 15 to 18 months, 200 words at 18 to 30 months, 14,000 words at six-years-old and then over 50,000 words by the time we leave secondary school.

The researchers found the genetic link during the ages of 15 to 18 months when toddlers typically communicate with single words only before their linguistic skills advance to two-word combinations and more complex grammatical structures.

The results, published in Nature Communications today [16 Sept], shed further light on a specific genetic region on chromosome 3, which has been previously implicated in dyslexia and speech-related disorders.

The ROBO2 gene contains the instructions for making the ROBO2 protein. This protein directs chemicals in brain cells and other neuronal cell formations that may help infants to develop language but also to produce sounds.

The ROBO2 protein also closely interacts with other ROBO proteins that have previously been linked to problems with reading and the storage of speech sounds.

Dr Beate St Pourcain, who jointly led the research with Professor Davey Smith at the MRC Integrative Epidemiology Unit, said: “This research helps us to better understand the genetic factors which may be involved in the early language development in healthy children, particularly at a time when children speak with single words only, and strengthens the link between ROBO proteins and a variety of linguistic skills in humans.”

Dr Claire Haworth, one of the lead authors, based at the University of Warwick, commented: “In this study we found that results using DNA confirm those we get from twin studies about the importance of genetic influences for language development. This is good news as it means that current DNA-based investigations can be used to detect most of the genetic factors that contribute to these early language skills.”

The study was carried out by an international team of scientists from the EArly Genetics and Lifecourse Epidemiology Consortium (EAGLE) and involved data from over 10,000 children.

Journal Reference:

Beate St Pourcain, Rolieke A.M. Cents, Andrew J.O. Whitehouse, Claire M.A. Haworth, Oliver S.P. Davis, Paul F. O’Reilly, Susan Roulstone, Yvonne Wren, Qi W. Ang, Fleur P. Velders, David M. Evans, John P. Kemp, Nicole M. Warrington, Laura Miller, Nicholas J. Timpson, Susan M. Ring, Frank C. Verhulst, Albert Hofman, Fernando Rivadeneira, Emma L. Meaburn, Thomas S. Price, Philip S. Dale, Demetris Pillas, Anneli Yliherva, Alina Rodriguez, Jean Golding, Vincent W.V. Jaddoe, Marjo-Riitta Jarvelin, Robert Plomin, Craig E. Pennell, Henning Tiemeier, George Davey Smith. Common variation near ROBO2 is associated with expressive vocabulary in infancy. Nature Communications, 2014; 5: 4831 DOI:10.1038/ncomms5831

The original Eskimos have no living descendants, say scientists (The Christian Science Monitor)

29/08/2014UncategorizedÍndios, Esquimós, Genética, Genealogiarenzotaddei

By Charles Choi, LiveScience Contributing Writer / August 28, 2014

Ancient human DNA is shedding light on the peopling of the Arctic region of the Americas, revealing that the first people there did not leave any genetic descendants in the New World, unlike previously thought.

The study’s researchers suggest the first group of people in the New World Arctic may have lived in near-isolation for more than 4,000 years because of a mindset that eschewed adopting new ideas. It remains a mystery why they ultimately died off, they added.

The first people in the Arctic of the Americas may have arrived about 6,000 years ago, crossing the Bering Strait from Siberia. The area was the last region of the New World that humans populated due to its harsh and frigid nature.

But the details of how the New World Arctic was peopled remain a mystery because the region’s vast size and remoteness make it difficult to conduct research there. For example, it was unclear whether the Inuit people living there today and the cultures that preceded them were genetically the same people, or independent groups.

The scientists analyzed DNA from bone, teeth and hair samples collected from the remains of 169 ancient humans from Arctic Siberia, Alaska, Canada and Greenland. They also sequenced the complete genomes of seven modern-day people from the region for comparison.

Previous research suggested people in the New World Arctic could be divided into two distinct groups — the Paleo-Eskimos, who showed up first, and the Neo-Eskimos, who got there nearly 4,000 years later. [In Photos: Life in the Arctic region of the Americas]

The early Paleo-Eskimo people include the Pre-Dorset and Saqqaq cultures, who mostly hunted reindeer and musk ox. When a particularly cold period began about 800 B.C., the Late Paleo-Eskimo people known as the Dorset culture emerged. The Dorset people had a more marine lifestyle, involving whaling and seal hunting. Their culture is divided into three phases, altogether lasting about 2,100 years.

“One may almost say kind of jokingly or informally that the Dorsets were the hobbits of the Eastern Arctic, a very strange and very conservative people that we are just now getting to know a little bit,” said study co-author William Fitzhugh, an anthropologist at the Smithsonian Institution’s National Museum of Natural History in Washington, D.C.

The Dorset culture ended sometime between 1150 and 1350 A.D., getting rapidly replaced after the sudden appearance of Neo-Eskimo whale-hunters known as the Thule culture. These newcomers from the Bering Strait region brought new technology from Asia, including complex weapons such as sinew-backed bows and more effective means of transportation such as dog sleds. The Thule “pioneered the hunting of large whales for the first time ever in, I guess, maybe anywhere in the world,” Fitzhugh said.

Modern Inuit cultures emerged from the Thule during the decline of whaling near the end of the period known as the Little Ice Age, which lasted from the 16th to 19th century. This ultimately led the Inuit to adopt the hunting of walruses at the edges of ice packs and the hunting of seals at their breathing holes.

Previous studies hinted that some modern Native Americans, such as the Athabascans in northwestern North America, might be descended from the Paleo-Eskimos. However, these findings now quash that idea. “The results of this paper have a bearing not just on the peopling of the Arctic, but also the peopling of the Americas,” lead study author Maanasa Raghavan, a molecular biologist at the University of Copenhagen’s National Museum of Natural History in Denmark, told Live Science.

The new findings suggest the Paleo-Eskimos apparently survived in near-isolation for more than 4,000 years. The arrival of Paleo-Eskimos into the Americas was its own independent migration event, with Paleo-Eskimos genetically distinct from both the Neo-Eskimos and modern Native Americans.

“I was actually surprised that we don’t find any evidence of mixture between Native Americans and Paleo-Eskimos,” said study co-author Eske Willerslev, an evolutionary geneticist also at the University of Copenhagen’s National Museum of Natural History. “In other studies, when we see people meeting each other, they might be fighting each other, but normally they actually also have sex with each other, but that doesn’t seem to really have been the case here. They must have been coexisting for thousands of years, so at least from a genetic point of view, the lack of mixture between those two groups was a bit surprising.”

The reason the Paleo-Eskimos may not have mixed with the Neo-Eskimos or the ancestors of modern Native Americans was “because they had such an entirely different mindset,” Fitzhugh said. “Their religions were completely different, their resources and their technologies were different. When you have people who are so close to nature as the Paleo-Eskimos had to be to survive, they had to be extremely careful about maintaining good relationships with the animals, and that meant not polluting the relationship by introducing new ideas, new rituals, new materials and so forth.”

The researchers did find evidence of gene flow between Paleo-Eskimos and Neo-Eskimos. However, this likely occurred before the groups migrated to the New World, back in Siberia, among the common ancestors of both lineages. The new evidence suggests that in the American Arctic, the two groups largely stayed separate.

In addition, while differences in the artifacts and architecture of the Pre-Dorset and Dorset had led previous studies to suggest they had different ancestral populations, these new findings suggest the Early and Late Paleo-Eskimos did share a common ancestral group. “The pre-Dorset people, the Dorset ancestors, seemed to have morphed into Dorset culture,” Fitzhugh told Live Science.

One mystery these findings help solve is the origin of the Sadlermiut people, who survived until the beginning of the 20th century in the region near Canada’s Hudson Bay, until the last of them perished from a disease introduced by whalers. The Sadlermiut avoided interaction with everyone outside their own society, and according to their Inuit neighbors, the Sadlermiut spoke a strange dialect, were bad at skills the Inuit considered vital, such as constructing igloos and tending oil lamps, were unclean, and did not observe standard Inuit taboos, all of which suggested that the Sadlermiut were descended from Paleo-Eskimos instead of Neo-Eskimos.

However, these new findings revealed the Sadlermiut showed evidence of only Inuit ancestry. Their cultural differences from other Inuit may have been the result of their isolation.

It remains a mystery why the Dorset people ultimately died off. Previous studies suggested the Dorset were absorbed by the expanding Thule population — and the Thule did adopt Dorset harpoon types, soapstone lamps and pots, and snow houses. However, these new findings do not find evidence of interbreeding between the groups.

One possibility is that the rise of the Thule represented “an example of prehistoric genocide,” Fitzhugh said. “The lack of significant genetic mixing might make it appear so.” However, Thule legends of the Dorset “tell only of friendly relations with a race of gentle giants,” Fitzhugh added.

Another possibility is that diseases introduced by Vikings or the Thule may have triggered the collapse of the Dorset, Fitzhugh said. However, “if it’s disease, then you’d expect to find dead bodies of Dorset people in their houses, and that’s never been found,” Fitzhugh said. [Fierce Fighters: 7 Secrets of Viking Seamen]

To help solve this and other remaining mysteries about the peopling of the New World Arctic, the researchers plan to look at more ancient human remains in both the Americas and Asia. The scientists detailed their findings in the Aug. 29 issue of the journal Science.

US Scientists, Oil Giant Stole Indigenous Blood (Common Dreams)

19/06/2014UncategorizedÍndios, ciência, Direitos humanos, Equador, Genética, Sangue, Visceralidaderenzotaddei

Published on Wednesday, June 18, 2014 by Common Dreams

For years, scientists working with Maxus Energy took blood samples from hundreds of Amazonian tribal members

– Max Ocean, editorial intern

Members of the Ecuadorean indigenous group known as the Huaorani (Credit: Jean-François Renaud/cc/flickr)

U.S. scientists working together with oil company Maxus Energy took around 3,500 blood samples from the indigenous Amazonian tribe known as the Huaorani, Ecuador charged on Monday.

The Huaorani are known for a unique genetic makeup that makes them immune to certain diseases.

René Ramírez, the head of the Ecuadorian Ministry of Higher Education, Science and Technology, told Ecuador state TV on Monday that samples were taken from around 600 Huaorani, and that multiple pints of blood were taken from many members of the tribe. Ramírez said that it is not yet known whether the samples have resulted in any commercial gains, but that samples were sold for scientific research.

According to an initial investigation two years ago, “It was demonstrated that the Coriell Institute has in its stores samples (from the Huaorani) and that it sells genetic material from the Huaorani people.” Harvard University was among the purchasers. Specifically, the 2012 report found that since 1994, seven cell cultures and 36 blood samples were distributed to eight different countries.

In the same report the Huaorani said that scientists had tricked them into allowing their blood to be taken between 1990 and 1991; however, President Rafael Correa said that there is now evidence that samples were taken as far back as the 1970s “in complicity with the oil company operating in the area.”

The Huaorani allegedly agreed to give the blood samples because scientists lied to them about why the samples were being taken. They were told the samples were being taken for medical tests, but never received results.

According to the website Hispanically Speaking News, in his weekly radio address on Saturday, President Correa said that at least 31 research papers were written between 1989 and 2012 based on the blood samples obtained––all without the consent of the Huaorani or the royalty payments normally required.

The taking of the samples was illegal, as Ecuador’s constitution bans the use of scientific research including genetic material in violation of human rights.

According to AFP, when the allegations first emerged in 2012, the U.S. Embassy said it was not aware of the case, and they did not immediately issue a response after Ecuador brought the charges on Monday.

What gave us the advantage over extinct types of humans? (The Hebrew University of Jerusalem)

22/04/2014UncategorizedEpigenética, Evolucionismo, Genéticarenzotaddei

22-Apr-2014

Jerry Barach

The answer lies in changes in the way our genes work

Jerusalem, April 22, 2014 — In parallel with modern man (Homo sapiens), there were other, extinct types of humans with whom we lived side by side, such as Neanderthals and the recently discovered Denisovans of Siberia. Yet only Homo sapiens survived. What was it in our genetic makeup that gave us the advantage?

The truth is that little is known about our unique genetic makeup as distinguished from our archaic cousins, and how it contributed to the fact that we are the only species among them to survive. Even less is known about our unique epigenetic makeup, but it is exactly such epigenetic changes that may have shaped our own species.

While genetics deals with the DNA sequence itself and the heritable changes in the DNA (mutations), epigenetics deals with heritable traits that are not caused by mutations. Rather, chemical modifications to the DNA can efficiently turn genes on and off without changing the sequence. This epigenetic regulatory layer controls where, when and how genes are activated, and is believed to be behind many of the differences between human groups.

Indeed, many epigenetic changes distinguish us from the Neanderthal and the Denisovan, researchers at the Hebrew University of Jerusalem and Europe have now shown.

In an article just published in Science, Dr. Liran Carmel, Prof. Eran Meshorer and David Gokhman of the Alexander Silberman Institute of Life sciences at the Hebrew University, along with scientists from Germany and Spain, have reconstructed, for the first time, the epigenome of the Neanderthal and the Denisovan. Then, by comparing this ancient epigenome with that of modern humans, they identified genes whose activity had changed only in our own species during our most recent evolution.

Among those genetic pattern changes, many are expressed in brain development. Numerous changes were also observed in the immune and cardiovascular systems, whereas the digestive system remained relatively unchanged.

On the negative side, the researchers found that many of the genes whose activity is unique to modern humans are linked to diseases like Alzheimer’s disease, autism and schizophrenia, suggesting that these recent changes in our brain may underlie some of the psychiatric disorders that are so common in humans today.

By reconstructing how genes were regulated in the Neanderthal and the Denisovan, the researchers provide the first insight into the evolution of gene regulation along the human lineage and open a window to a new field that allows the studying of gene regulation in species that went extinct hundreds of thousands of years ago.

Genetic study tackles mystery of slow plant domestications (Science Daily)

19/04/2014UncategorizedAgricultura, Domesticação das plantas, Genéticarenzotaddei

Date: April 17, 2014

Source: Washington University in St. Louis

Summary: Did domesticating a plant typically take a few hundred or many thousands of years? Genetic studies often indicate that domestication traits have a fairly simple genetic basis, which should facilitate their rapid evolution under selection. On the other hand, recent archeological studies of crop domestication have suggested a relatively slow spread and fixation of domestication traits. A new article tries to resolve the discrepancy.

Closeup of a mature seedhead of foxtail millet. Like other domesticated cereals, foxtail millet has nonshattering spikes that retain their seeds during harvesting. Credit: © Ruud Morijn / Fotolia

“The Modern View of Domestication,” a special feature of TheProceedings of the National Academy of Sciences (PNAS) published April 29, raises a number of startling questions about a transition in our deep history that most of us take for granted. At the end of the last Ice Age, people in many spots around the globe shifted from hunting animals and gathering fruits and tubers to cultivating livestock and plants.

It seems so straightforward and yet the more scientists learn, the more complex the story becomes. Recently, geneticists and archeologists working on domestication compared notes and up popped a question of timing. Did domesticating a plant typically take a few hundred or many thousands of years?

Genetic studies often indicate that domestication traits have a fairly simple genetic basis, which should facilitate their rapid evolution under selection. On the other hand, recent archeological studies of crop domestication have suggested a relatively slow spread and fixation of domestication traits.

In this special issue of PNAS, Washington University in St. Louis biologist Ken Olsen, PhD, and colleagues ask whether complex genetic interactions might have slowed the rate at which early farmers were able to shape plant characteristics, thus reconciling the genetic and archeological findings.

Olsen, associate professor in the Department of Biology in Arts & Sciences, together with colleagues from Oklahoma State University and the University of Guelph in Ontario, Canada, conclude that these interactions are not a key factor in domesticated plants. The process of domestication, Olsen said, favored gene variants (alleles) that are relatively insensitive to background effects and highly responsive to selection.

But finding these alleles in the first place must have difficult, Olsen said. Only a subset of the genes in the wild population would have reliably produced a favored trait regardless of the crop variety into which they were bred and regardless of where that crop was grown. So the early stages of domestication might have been beset by setbacks and incomprehensible failures that might help explain the lag in the archeological record.

“What we are learning suggests there’s a whole lot of diversity out there in wild relatives of crop plants or even in landraces, varieties of plants and animals that are highly adapted to local conditions,” Olsen said, “that wasn’t tapped during the domestication process.”

“These plant populations could provide the diversity for continued breeding that is going to be very important as the world faces climatic change,” he said. “This is why it is important we understand the early stages of domestication.”

Two possible speed bumps

Many crops are distinguished from their wild ancestors with a suite of traits called the domestication syndrome. This includes seeds that remain attached to the plant for harvesting (a trait called nonshattering), reduced branching and robust growth of the central stem and bigger fruits, seeds or tubers.

Over the past 20 years, researchers have begun to identify the genes that control some of the most important domestication traits, no easy task in the days before rapid sequencing, because they had to start with plant traits and work back to unknown genes.

This work showed that many domestication traits were under the control of single genes. For example the gene teosinte branched1 (tb1) converts highly branched teosinte plants into single stalks of corn.

But the seeming importance of single genes could have been an artifact of the method used to identify domestication genes, which required the researcher to pick “candidate” genes and, perhaps, prematurely narrow the search, overlooking indirect genetic effects.

“Little is known about the underlying genetics of domestication,” Olsen said. “We decided to look at genetic mechanisms for modifying plant phenotypes that hadn’t been explored before, in part because not much data is available.”

The new work examines the possibility that two indirect effects — the influence of the genetic background on the expression of a gene (called epistasis) and the effects of the environment on the expression of genes — might have slowed the selection of plants with the desired traits.

Epistasis and environmental effects in domestication genes

By selecting animals for coat color, animal breeders may have stabilized certain epistatic and environmental interactions in companion animals (see photos at right). But when the plant scientists looked at comparable genetic mechanisms in domesticated plants, they found the reverse to be true. Farmers seem to have selected for plant variants that were insensitive to epistatic and environmental interactions.

Shattering in domesticated foxtail millet provides an example of insensitivity to epistasis. Branching in maize illustrates insensitivity to environmental effects.

Shattering in foxtail millet and its wild ancestor, green millet, is controlled by two stretches of DNA containing or linked to genes that underlie this trait, a major one called QTL 1 and a minor one called QTL2. In this as in other epistatic interactions, the effect of an allele at one location depends on the state of the allele at the other location. But when wild and domesticated plants are crossed, these “genetic background effects” are not symmetric.

Shattering in plants with a wild green-millet allele at the QTLI location depends on the allele at the QTL2 location. In contrast, shattering in plants with the foxtail-millet allele at QTL1 is unaffected by the allele at the QTL2 location.

In the limited number of examples at their disposal, the scientists found it to be generally true that that domesticated alleles were less sensitive to genetic background than wild alleles. The domestication genes, in other words, tended to be ones that would produce the same result even if they were introduced into a different crop variety.

Teosinte provides a good example of the sensitivity of gene expression to the environment. Teosinte is strongly affected by crowding. When a teosinte plant with a wild tb1 gene is repeatedly backcrossed with maize, it produces highly branched plants in uncrowded growing conditions but plants with smaller lateral branches when it is crowded.

Again, however, the effect is not symmetric. The domesticated trait is less sensitive to the environment than the wild trait; plants with the domesticated tb1 gene allele are unbranched whether or not they are crowded.

Unlike companion-animal breeders, early farmers seem to have selected domestication-gene alleles that are insensitive to genetic background and to the environment. This process would have been slow, unrewarding and difficult to understand, because the effects of gene variants on the plant weren’t stable. But once sensitive alleles had been replaced with robust ones, breeders would have been able to exert strong selection pressure on plant traits, shaping them much more easily than before, and the pace of domestication would have picked up.

No wonder the archeological record indicates there were false starts, failed efforts and long delays.

Revolução neandertal (Folha de S.Paulo)

07/03/2014UncategorizedAntropologia, Antropologia física, Genética, Neandertaisrenzotaddei

JC e-mail 4907, de 07 de março de 2014

Svante Pääbo, cientista que liderou o mapeamento do genoma do homem de Neandertal, conta em livro sua descoberta que abalou a antropologia

A história de como os humanos deixaram a África e povoaram o resto do mundo tem hoje seu foco em pesquisas sobre o DNA, deixando os fósseis –matéria-prima indispensável da antropologia– meio fora dos holofotes. Há quem questione se essa mudança é benéfica, mas é difícil desvincular essa revolução acadêmica do nome de um cientista: Svante Pääbo.

Em novo livro, o geneticista sueco radicado na Alemanha conta como essa mudança de perspectiva se instalou. Para tal, narra a história de seu principal objetivo científico, o sequenciamento do genoma do homem de Neandertal, a última criatura do gênero Homo a pisar na Terra antes de o Homo sapiens tomar o planeta inteiro para si.

Pääbo é o sujeito magricela que aparece em uma fotografia estampada em vários jornais em 7 de maio de 2010 na qual está olhando para um crânio de neandertal. Naquele dia, quando o cientista publicou a primeira versão do genoma do hominídeo extinto, teorias de evolução humana baseadas apenas na interpretação do formato de fósseis começaram a ter de ser alteradas para acomodar algumas revelações.

Aquela que chamou mais a atenção, sem dúvida, foi a de que H. sapiens e H. neanderthalensis legaram ao planeta os frutos de uma inusitada história de amor. Pessoas de etnias europeias ainda carregam no DNA cerca de 3% de ancestralidade neandertal.

O genoma desse hominídeo e a descoberta subsequente de uma linhagem totalmente nova do gênero Homo –os denisovanos, descritos por Pääbo com base no DNA extraído de um único osso de dedo– mostraram que a saída da África foi um processo bem mais complexo.

Achar DNA em ossos com dezenas de milhares de anos, porém, não era (e não é) coisa trivial. Pääbo, que se descreve como um sujeito paranoico por limpeza (para evitar contaminar amostras), também exigia de si repetir seus experimentos inúmeras vezes, cada vez que obtinha um bom resultado. Não poupa, por isso, criticas às revistas “Science” e “Nature” por terem publicado estudos que considera de baixo padrão.

Com o modesto título “Neanderthal Man”, o livro conta muito mais do que a história do sequenciamento de um genoma. Pääbo começou sua carreira acadêmica patinando entre disciplinas tão distintas quanto egiptologia e bioquímica. Seu ponto de virada foi a extração de DNA de uma múmia egípcia, estudo que realizou escondido de seu orientador de doutorado, usando uma amostra cedida por um museu da Alemanha Oriental. (O curador que cedeu o pedaço de múmia foi depois abordado pela Stasi, a polícia comunista.)

Uma boa parte do livro é dedicada a tecnicalidades de extração de DNA, apesar de as histórias de negociações para obtenção de fósseis serem mais interessantes.

No meio dos trabalhos de sequenciamento do neandertal, Pääbo conta sobre o racha com seu colaborador Ed Rubin, do Laboratório Nacional Lawrence Berkeley, que passou a competir diretamente por amostras de fósseis.

Além de intriga, há também um bocado de romance para o que se espera de um livro de ciência. Abertamente bissexual, Pääbo não se intimida em contar a história de um triângulo amoroso que envolveu sua mulher e outro cientista de seu instituto.

Nada disso, porém, é narrado mais passionalmente do que a epopeia científica do genoma do neandertal, que mudou a noção sobre o que significa ser humano.

(Rafael Garcia/Folha de S.Paulo)
http://www1.folha.uol.com.br/fsp/cienciasaude/155225-revolucao-neandertal.shtml

A challenge to the genetic interpretation of biology (University of Eastern Finland)

20/02/2014UncategorizedFísica, Genética, Mediação tecnológica, Saúderenzotaddei

19-Feb-2014

Keith Baverstock

A proposal for reformulating the foundations of biology, based on the 2nd law of thermodynamics and which is in sharp contrast to the prevailing genetic view, is published today in the Journal of the Royal Society Interface under the title “Genes without prominence: a reappraisal of the foundations of biology”. The authors, Arto Annila, Professor of physics at Helsinki University and Keith Baverstock, Docent and former professor at the University of Eastern Finland, assert that the prominent emphasis currently given to the gene in biology is based on a flawed interpretation of experimental genetics and should be replaced by more fundamental considerations of how the cell utilises energy. There are far-reaching implications, both in research and for the current strategy in many countries to develop personalised medicine based on genome-wide sequencing.

This shows the inactive linear peptide molecule with a sequence of amino acids derived from the gene coding sequence folds to a protein.

Is it in your genes?

By “it” we mean intelligence, sexual orientation, increased risk of cancer, stroke or heart attack, criminal behaviour, political preference and religious beliefs, etcetera. Genes have been implicated in influencing, wholly or partly, all these aspects of our lives by researchers. Genes cannot cause any of these features, although geneticists have found associations between specific genes and all of these features, many of which are entirely spurious and a few are fortuitous.

How can we be so sure?

When a gene, a string of bases on the DNA molecule, is deployed, it is first transcribed and then translated into a peptide – a string of amino acids. To give rise to biological properties it needs to “fold” into a protein.

This process consumes energy and is therefore governed by the 2nd law, but also by the environment in which the folding takes place. These two factors mean that there is no causal relationship between the original gene coding sequence and the biological activity of the protein.

Is there any empirical evidence to support this?

Yes, a Nordic study of twins conducted in 2000 showed there was no evidence that cancer was a “genetic” disease – that is – that genes play no role in the causation of cancer. A wider international study involving 50,000 identical twin pairs published in 2012, showed that this conclusion applied to other common disease as well. Since the sequencing of the human genome was completed in 2001 it has not proved possible to relate abnormal gene sequences to common diseases giving rise to the problem of the “missing heritability”.

What is the essence of the reformulation?

At the most fundamental level organisms are energy-consuming systems and the appropriate foundation in physics is that of complex dissipative systems. As energy flows in and out and within, the complex molecular system called the cell, fundamental physical considerations, dictated by the 2nd law of thermodynamics, demand that these flows, called actions, are maximally efficient (follow the path of least resistance) in space and time. Energy exchanges can give rise to new emergent properties that modify the actions and give rise to more new emergent properties and so on. The result is evolution from simpler to more complex and diverse organisms in both form and function, without the need to invoke genes. This model is supported by earlier computer simulations to create a virtual ecosystem by Mauno Rönkkö of the University of Eastern Finland.

What implications does this have in practice?

There are many, but two are urgent.

1) to assume that genes are unavoidable influences on our health and behaviour will distract attention from the real causes of disease, many of which arise from our environment;

2) the current strategy towards basing healthcare on genome-wide sequencing, so called “personalised healthcare”, will prove costly and ineffective.

What is personalised health care?

This is the idea that it will be possible to predict at birth, by determining the total DNA sequence (genome-wide sequence), health outcomes in the future and take preventive measures. Most European countries have research programmes in this and in the UK a pilot study with 100,000 participants is underway.

Modelo pode ajudar a prever como espécies da Mata Atlântica responderão às mudanças climáticas (Fapesp)

11/02/2014UncategorizedBiologia, Clima, Ecologia, Genética, Incerteza, Meio ambiente, Mudanças climáticas, Previsãorenzotaddei

Pesquisadores do Brasil e dos EUA buscam compreensão dos processos evolutivos, geológicos, climáticos e genéticos por trás do padrão atual da biodiversidade (foto:Samuel Iavelberg)

11/02/2014

Por Karina Toledo

Agência FAPESP – Compreender os processos evolutivos, geológicos, climáticos e genéticos por trás da enorme biodiversidade e do padrão de distribuição de espécies da Mata Atlântica e, com base nesse conhecimento, criar modelos que permitam prever, por exemplo, como essas espécies vão reagir às mudanças no clima e no uso do solo.

Esse é o objetivo central de um projeto que reúne pesquisadores do Brasil e dos Estados Unidos no âmbito de um acordo de cooperação científica entre o Programa de Pesquisas em Caracterização, Conservação, Recuperação e Uso Sustentável da Biodiversidade do Estado de São Paulo (BIOTA-FAPESP) e o programa Dimensions of Biodiversity, da agência federal norte-americana de fomento à pesquisa National Science Foundation (NSF).

“Além de ajudar a prever o que poderá ocorrer no futuro com as espécies, os modelos ajudam a entender como está hoje distribuída a biodiversidade em áreas onde os cientistas não têm acesso. Como fazemos coletas por amostragem, seria impossível mapear todos os microambientes. Os modelos permitem extrapolar essas informações para áreas não amostradas e podem ser aplicados em qualquer tempo”, explicou Ana Carolina Carnaval, professora da The City University of New York, nos Estados Unidos, e coordenadora do projeto de pesquisa ao lado de Cristina Miyaki, do Instituto de Biociências da Universidade de São Paulo (IB-USP).

A proposta, segundo Carnaval, é promover a integração de pesquisadores de diversas áreas – como ecologia, geologia, biogeografia, genética, fisiologia, climatologia, taxonomia, paleologia, geomorfologia – e unir ciência básica e aplicada em benefício da conservação da Mata Atlântica.

O bioma é considerado um dos 34 hotspots mundiais, ou seja, uma das áreas prioritárias para a conservação por causa de sua enorme biodiversidade, do alto grau de endemismo de suas espécies (ocorrência apenas naquele local) e da grande ameaça de extinção resultante da intensa atividade antrópica na região.

A empreitada coordenada por Carnaval e por Miyaki teve início no segundo semestre de 2013. A rede de pesquisadores esteve reunida pela primeira vez para apresentar suas linhas de pesquisa e seus resultados preliminares na segunda-feira (10/02), durante o “Workshop Dimensions US-BIOTA São Paulo – A multidisciplinary framework for biodiversity prediction in the Brazilian Atlantic forest hotspot”.

“Convidamos alguns colaboradores além de pesquisadores envolvidos no projeto, pois queremos críticas e sugestões que permitam aperfeiçoar os trabalhos”, contou Miyaki. “Essa reunião é um marco para conseguirmos efetivar a integração entre as diversas áreas do projeto e criarmos uma linguagem única focada em compreender a Mata Atlântica e os processos que fazem esse bioma ser tão especial”, acrescentou.

Entre os mistérios que os cientistas tentarão desvendar estão a origem da incrível diversidade existente na Mata Atlântica, possivelmente fruto de conexões existentes há milhões de anos com outros biomas, entre eles a Floresta Amazônica. Outra questão fundamental é entender a importância do sistema de transporte de umidade na região hoje e no passado e como ele permite que a Mata Atlântica se comunique com outros sistemas florestais. Também está entre as metas do grupo investigar como a atividade tectônica influenciou o curso de rios e afetou o padrão de distribuição das espécies aquáticas.

Desafios do BIOTA

Durante a abertura do workshop, o presidente da FAPESP, Celso Lafer, realçou a importância de abordagens inovadoras e multidisciplinares voltadas para a proteção da biodiversidade da Mata Atlântica. Ressaltou ainda que a iniciativa está em consonância com os esforços de internacionalização realizados pela FAPESP nos últimos anos.

“Uma das grandes preocupações da FAPESP tem sido o processo de internacionalização, que basicamente está relacionado ao esforço de juntar pesquisadores de diversas áreas para avançar no conhecimento. Este programa de hoje está relacionado a aspirações dessa natureza e tenho certeza de que os resultados serão altamente relevantes”, afirmou Lafer.

Também durante a mesa de abertura, o diretor do IB-USP, Carlos Eduardo Falavigna da Rocha, afirmou que o programa BIOTA-FAPESP tem sido um exemplo para outros estados e outras fundações de apoio à pesquisa em âmbito federal e estadual.

Carlos Alfredo Joly, professor da Universidade Estadual de Campinas (Unicamp) e coordenador do BIOTA-FAPESP, apresentou um histórico das atividades realizadas pelo programa desde 1999, entre elas a elaboração de um mapa de áreas prioritárias para conservação que serviu de base para mais de 20 documentos legais estaduais – entre leis, decretos e resoluções.

Joly também falou sobre os desafios a serem vencidos até 2020, como empreender esforços de restauração e de reintrodução de espécies, ampliar o entendimento sobre ecossistemas terrestres e sobre os mecanismos que mantêm a biodiversidade no Estado e intensificar as atividades voltadas à educação ambiental.

Para 2014, Joly ressaltou dois desafios na área de conservação. “Estamos iniciando uma campanha para o tombamento da Serra da Mantiqueira. Já fizemos alguns artigos de jornais, estamos lançando um website específico e vamos trabalhar para conseguir tombar regiões acima de 800 metros, áreas apontadas como de extrema prioridade para conservação no atlas do BIOTA”, disse.

Outra meta para 2014, segundo Joly, é trabalhar para que o Brasil ratifique o protocolo de Nagoya – tratado internacional que dispõe sobre a repartição de benefícios do uso da biodiversidade – até outubro, quando ocorrerá a 12ª Conferência das Partes da Convenção sobre Diversidade Biológica.

“É fundamental que um país megadiverso, que tem todo o interesse de ter sua biodiversidade protegida por esse protocolo internacional, se torne signatário do protocolo antes dessa reunião”, afirmou Joly.

New application of physics tools used in biology (Science Daily)

10/02/2014UncategorizedBiologia, Epigenética, Física, Genética, Interdisciplinaridaderenzotaddei

Date:

February 7, 2014

Source: DOE/Lawrence Livermore National Laboratory

Summary: A physicist and his colleagues have found a new application for the tools and mathematics typically used in physics to help solve problems in biology.

This DNA molecule is wrapped twice around a histone octamer, the major structural protein of chromosomes. New studies show they play a role in preserving biological memory when cells divide. Image courtesy of Memorial University of Newfoundland. Credit: Image courtesy of DOE/Lawrence Livermore National Laboratory

A Lawrence Livermore National Laboratory physicist and his colleagues have found a new application for the tools and mathematics typically used in physics to help solve problems in biology.

Specifically, the team used statistical mechanics and mathematical modeling to shed light on something known as epigenetic memory — how an organism can create a biological memory of some variable condition, such as quality of nutrition or temperature.

“The work highlights the interdisciplinary nature of modern molecular biology, in particular, how the tools and models from mathematics and physics can help clarify problems in biology,” said Ken Kim, a LLNL physicist and one of the authors of a paper appearing in the Feb. 7 issue ofPhysical Review Letters.

Not all characteristics of living organisms can be explained by their genes alone. Epigenetic processes react with great sensitivity to genes’ immediate biochemical surroundings — and further, they pass those reactions on to the next generation.

The team’s work on the dynamics of histone protein modification is central to epigenetics. Like genetic changes, epigenetic changes are preserved when a cell divides. Histone proteins were once thought to be static, structural components in chromosomes, but recent studies have shown that histones play an important dynamical role in the machinery responsible for epigenetic regulation.

When histones undergo chemical alterations (histone modification) as a result of some external stimulus, they trigger short-term biological memory of that stimulus within a cell, which can be passed down to its daughter cells. This memory also can be reversed after a few cell division cycles.

Epigenetic modifications are essential in the development and function of cells, but also play a key role in cancer, according to Jianhua Xing, a former LLNL postdoc and current professor at Virginia Tech. “For example, changes in the epigenome can lead to the activation or deactivation of signaling pathways that can lead to tumor formation,” Xing added.

The molecular mechanism underlying epigenetic memory involves complex interactions between histones, DNA and enzymes, which produce modification patterns that are recognized by the cell. To gain insight into such complex systems, the team constructed a mathematical model that captures the essential features of the histone-induced epigenetic memory. The model highlights the “engineering” challenge a cell must constantly face during molecular recognition. It is analogous to restoring a picture with missing parts. The molecular properties of a species have been evolutionarily selected to allow them to “reason” what the missing parts are based on incomplete information pattern inherited from the mother cell.

Story Source:

The above story is based on materials provided by DOE/Lawrence Livermore National Laboratory. The original article was written by Anne M Stark. Note: Materials may be edited for content and length.

Humanity’s forgotten return to Africa revealed in DNA (New Scientist)

04/02/2014UncategorizedAntropologia física, Evolução, Genética, Hominídeosrenzotaddei

20:00 03 February 2014 by Catherine Brahic

Call it humanity’s unexpected U-turn. One of the biggest events in the history of our species is the exodus out of Africa some 65,000 years ago, the start ofHomo sapiens‘ long march across the world. Now a study of southern African genes shows that, unexpectedly, another migration took western Eurasian DNA back to the very southern tip of the continent 3000 years ago.

According to conventional thinking, the Khoisan tribes of southern Africa, have lived in near-isolation from the rest of humanity for thousands of years. In fact, the study shows that some of their DNA matches most closely people from modern-day southern Europe, including Spain and Italy.

Because Eurasian people also carry traces of Neanderthal DNA, the finding also shows – for the first time – that genetic material from our extinct cousin may be widespread in African populations.

The Khoisan tribes of southern Africa are hunter-gatherers and pastoralists who speak unique click languages. Their extraordinarily diverse gene pool split from everyone else’s before the African exodus.

Ancient lineages

“These are very special, isolated populations, carrying what are probably the most ancient lineages in human populations today,” says David Reich of Harvard University. “For a lot of our genetic studies we had treated them as groups that had split from all other present-day humans before they had split from each other.”

So he and his colleagues were not expecting to find signs of western Eurasian genes in 32 individuals belonging to a variety of Khoisan tribes. “I think we were shocked,” says Reich.

The unexpected snippets of DNA most resembled sequences from southern Europeans, including Sardinians, Italians and people from the Basque region (see “Back to Africa – but from where?“). Dating methods suggested they made their way into the Khoisan DNA sometime between 900 and 1800 years ago – well before known European contact with southern Africa (see map).

Archaeological and linguistic studies of the region can make sense of the discovery. They suggest that a subset of the Khoisan, known as the Khoe-Kwadi speakers, arrived in southern Africa from east Africa around 2200 years ago. Khoe-Kwadi speakers were – and remain – pastoralists who make their living from herding cows and sheep. The suggestion is that they introduced herding to a region that was otherwise dominated by hunter-gatherers.

Khoe-Kwadi tribes

Reich and his team found that the proportion of Eurasian DNA was highest in Khoe-Kwadi tribes, who have up to 14 per cent of western Eurasian ancestry. What is more, when they looked at the east African tribes from which the Khoe-Kwadi descended, they found a much stronger proportion of Eurasian DNA – up to 50 per cent.

That result confirms a 2012 study by Luca Pagani of the Wellcome Trust Sanger Institute in Hinxton, UK, which found non-African genes in people living in Ethiopia. Both the 2012 study and this week’s new results show that the Eurasian genes made their way into east African genomes around 3000 years ago. About a millennium later, the ancestors of the Khoe-Kwadi headed south, carrying a weaker signal of the Eurasian DNA into southern Africa.

The cultural implications are complex and potentially uncomfortably close to European colonial themes. “I actually am not sure there’s any population that doesn’t have west Eurasian [DNA],” says Reich.

“These populations were always thought to be pristine hunter-gatherers who had not interacted with anyone for millennia,” says Reich’s collaborator, linguist Brigitte Pakendorf of the University of Lyon in France. “Well, no. Just like the rest of the world, Africa had population movements too. There was simply no writing, no Romans or Greeks to document it.”

Twist in tale

There’s one more twist to the tale. In 2010 a research team – including Reich – published the first draft genome of a Neanderthal. Comparisons with living humans revealed traces of Neanderthal DNA in all humans with one notable exception: sub-Saharan peoples like the Yoruba and Khoisan.

That made sense. After early humans migrated out of Africa around 60,000 years ago, they bumped into Neanderthals somewhere in what is now the Middle East. Some got rather cosy with each other. As their descendants spread across the world to Europe, Asia and eventually the Americas, they spread bits of Neanderthal DNA along with their own genes. But because those descendants did not move back into Africa until historical times, most of this continent remained a Neanderthal DNA-free zone.

Or so it seemed at the time. Now it appears that the Back to Africa migration 3000 years ago carried a weak Neanderthal genetic signal deep into the homeland. Indeed one of Reich’s analyses, published last month, found Neanderthal traces in Yoruba DNA (Nature, DOI: 10.1038/nature12886).

In other words, not only is western Eurasian DNA ancestry a global phenomenon, so is having a bit of Neanderthal living on inside you.

Journal reference: PNAS, DOI: 10.1073/pnas.1313787111

Back to Africa – but from where?

Reich and his colleagues found that DNA sequences in the Khoisan people most closely resemble some found in people who today live in southern Europe. That, however, does not mean the migration back to Africa started in Italy or Spain. More likely, the migration began in what is now the Middle East.

We know that southern Europeans can trace their ancestry to the Middle East. However, in the thousands of years since they – and the ancestors of the Khoisan – left the region, it has experienced several waves of immigration. These waves have had a significant effect on the genes of people living in the Middle East today, and and means southern Europeans are much closer to the original inhabitants of the Levant than modern-day Middle Easterners.

Neanderthals Leave Their Mark on Us (New York Times)

30/01/2014UncategorizedEvolução, Genética, Neandertaisrenzotaddei

JAN. 29, 2014

A reconstruction of a Neanderthal skeleton, right, with a modern human skeleton in the background. Frank Franklin II/Associated Press

By Carl Zimmer

Ever since the discovery in 2010 that Neanderthals interbred with the ancestors of living humans, scientists have been trying to determine how their DNA affects people today. Now two new studies have traced the history of Neanderthal DNA, and have pinpointed a number of genes that may have medical importance today.

Among the findings, the studies have found clues to the evolution of skin and fertility, as well as susceptibility to diseases like diabetes. More broadly, they show how the legacy of Neanderthals has endured 30,000 years after their extinction.

“It’s something that everyone wanted to know,” said Laurent Excoffier, a geneticist at the University of Bern in Switzerland who was not involved in the research.

Neanderthals, who became extinct about 30,000 years ago, were among the closest relatives of modern humans. They shared a common ancestor with us that lived about 600,000 years ago.

In the 1990s, researchers began finding fragments of Neanderthal DNA in fossils. By 2010 they had reconstructed most of the Neanderthal genome. When they compared it with the genomes of five living humans, they found similarities to small portions of the DNA in the Europeans and Asians.

The researchers concluded that Neanderthals and modern humans must have interbred. Modern humans evolved in Africa and then expanded out into Asia and Europe, where Neanderthals lived. In a 2012 study, the researchers estimated that this interbreeding took place between 37,000 and 85,000 years ago.

Sir Paul A. Mellars, an archaeologist at the University of Cambridge and the University of Edinburgh, who was not involved in the research, said the archaeological evidence suggested the opportunity for modern humans to mate with Neanderthals would have been common once they expanded out of Africa. “They’d be bumping into Neanderthals at every street corner,” he joked.

The first draft of the Neanderthal genome was too rough to allow scientists to draw further conclusions. But recently, researchers sequenced a far more accurate genome from a Neanderthal toe bone.

Scientists at Harvard Medical School and the Max Planck Institute for Evolutionary Anthropology in Germany compared this high-quality Neanderthal genome to the genomes of 1,004 living people. They were able to identify specific segments of Neanderthal DNA from each person’s genome.

“It’s a personal map of Neanderthal ancestry,” said David Reich of Harvard Medical School, who led the research team. He and his colleagues published their results in the journal Nature.

Living humans do not have a lot of Neanderthal DNA, Dr. Reich and his colleagues found, but some Neanderthal genes have become very common. That’s because, with natural selection, useful genes survive as species evolve. “What this proves is that these genes were helpful for non-Africans in adapting to the environment,” Dr. Reich said.

In a separate study published in Science, Benjamin Vernot and Joshua M. Akey of the University of Washington came to a similar conclusion, using a different method.

Mr. Vernot and Dr. Akey looked for unusual mutations in the genomes of 379 Europeans and 286 Asians. The segments of DNA that contained these mutations turned out to be from Neanderthals.

Both studies suggest that Neanderthal genes involved in skin and hair were favored by natural selection in humans. Today, they are very common in living non-Africans.

The fact that two independent studies pinpointed these genes lends support to their importance, said Sriram Sankararaman of Harvard Medical School, a co-author on the Nature paper. “The two methods seem to be converging on the same results.”

It is possible, Dr. Akey speculated, that the genes developed to help Neanderthal skin adapt to the cold climate of Europe and Asia.

But Dr. Akey pointed out that skin performs other important jobs, like shielding us from pathogens. “We don’t understand enough about the biology of those particular genes yet,” he said. “It makes it hard to pinpoint a reason why they’re beneficial.”

Both teams of scientists also found long stretches of the living human genomes where Neanderthal DNA was glaringly absent. This pattern could be produced if modern humans with certain Neanderthal genes could not have as many children on average as people without them. For example, living humans have very few genes from Neanderthals involved in making sperm. That suggests that male human-Neanderthal hybrids might have had lower fertility or were even sterile.

Overall, said Dr. Reich, “most of the Neanderthal genetic material was more bad than good.”

Some of the Neanderthal genes that have endured until today may be influencing people’s health. Dr. Reich and his colleagues identified nine Neanderthal genes in living humans that are known to raise or reduce the risk of various diseases, including diabetes and lupus.

To better understand the legacy of Neanderthals, Dr. Reich and his colleagues are collaborating with the UK Biobank, which collects genetic information from hundreds of thousands of volunteers. The scientists will search for Neanderthal genetic markers, and investigate whether Neanderthal genes cause any noticeable differences in anything from weight to blood pressure to scores on memory tests.

“This experiment of nature has been done,” said Dr. Reich, “and we can study it.”

Correction: January 29, 2014
An earlier version of this article misstated the living groups in which Neanderthal genes involved in skin and hair are very common. They are very common in non-Africans, not non-Asians.

Genomes of Modern Dogs and Wolves Provide New Insights On Domestication (Science Daily)

17/01/2014UncategorizedAnimais, Cães, Evolução, Genéticarenzotaddei

Jan. 16, 2014 — Dogs and wolves evolved from a common ancestor between 9,000 and 34,000 years ago, before humans transitioned to agricultural societies, according to an analysis of modern dog and wolf genomes from areas of the world thought to be centers of dog domestication.

This chart depicts wolf and dog lineages as they diverge over time. (Credit: Freedma, et al / PLoS Genetics)

The study, published in PLoS Geneticson January 16, 2014, also shows that dogs are more closely related to each other than wolves, regardless of geographic origin. This suggests that part of the genetic overlap observed between some modern dogs and wolves is the result of interbreeding after dog domestication, not a direct line of descent from one group of wolves.

This reflects a more complicated history than the popular story that early farmers adopted a few docile, friendly wolves that later became our beloved, modern-day companions. Instead, the earliest dogs may have first lived among hunter-gatherer societies and adapted to agricultural life later.

“Dog domestication is more complex than we originally thought,” said John Novembre, associate professor in the Department of Human Genetics at the University of Chicago and a senior author on the study. “In this analysis we didn’t see clear evidence in favor of a multi-regional model, or a single origin from one of the living wolves that we sampled. It makes the field of dog domestication very intriguing going forward.”

The team generated the highest quality genome sequences to date from three gray wolves: one each from China, Croatia and Israel, representing three regions where dogs are believed to have originated. They also produced genomes for two dog breeds: a basenji, a breed which originates in central Africa, and a dingo from Australia, both areas that have been historically isolated from modern wolf populations. In addition to the wolves and dogs, they sequenced the genome of a golden jackal to serve as an “outgroup” representing earlier divergence.

Their analysis of the basenji and dingo genomes, plus a previously published boxer genome from Europe, showed that the dog breeds were most closely related to each other. Likewise, the three wolves from each geographic area were more closely related to each other than any of the dogs.

Novembre said this tells a different story than he and his colleagues anticipated. Instead of all three dogs being closely related to one of the wolf lineages, or each dog being related to its closest geographic counterpart (i.e. the basenji and Israeli wolf, or the dingo and Chinese wolf), they seem to have descended from an older, wolf-like ancestor common to both species.

“One possibility is there may have been other wolf lineages that these dogs diverged from that then went extinct,” he said. “So now when you ask which wolves are dogs most closely related to, it’s none of these three because these are wolves that diverged in the recent past. It’s something more ancient that isn’t well represented by today’s wolves.”

Accounting for gene flow between dogs and wolves after domestication was a crucial step in the analyses. According to Adam Freedman, a postdoctoral fellow at the University of California, Los Angeles (UCLA) and the lead author on the study, gene flow across canid species appears more pervasive than previously thought.

“If you don’t explicitly consider such exchanges, these admixture events get confounded with shared ancestry,” he said. “We also found evidence for genetic exchange between wolves and jackals. The picture emerging from our analyses is that these exchanges may play an important role in shaping the diversification of canid species.”

Domestication apparently occurred with significant bottlenecks in the historical population sizes of both early dogs and wolves. Freedman and his colleagues were able to infer historical sizes of dog and wolf populations by analyzing genome-wide patterns of variation, and show that dogs suffered a 16-fold reduction in population size as they diverged from wolves. Wolves also experienced a sharp drop in population size soon after their divergence from dogs, implying that diversity among both animals’ common ancestors was larger than represented by modern wolves.

The researchers also found differences across dog breeds and wolves in the number of amylase (AMY2B) genes that help digest starch. Recent studies have suggested that this gene was critical to domestication, allowing early dogs living near humans to adapt to an agricultural diet. But the research team surveyed genetic data from 12 additional dog breeds and saw that while most dog breeds had high numbers of amylase genes, those not associated with agrarian societies, like the Siberian husky and dingo, did not. They also saw evidence of this gene family in wolves, meaning that it didn’t develop exclusively in dogs after the two species diverged, and may have expanded more recently after domestication.

Novembre said that overall, the study paints a complex picture of early domestication.

“We’re trying to get every thread of evidence we can to reconstruct the past,” he said. “We use genetics to reconstruct the history of population sizes, relationships among populations and the gene flow that occurred. So now we have a much more detailed picture than existed before, and it’s a somewhat surprising picture.”

Journal Reference:

Adam H. Freedman, Ilan Gronau, Rena M. Schweizer, Diego Ortega-Del Vecchyo, Eunjung Han, Pedro M. Silva, Marco Galaverni, Zhenxin Fan, Peter Marx, Belen Lorente-Galdos, Holly Beale, Oscar Ramirez, Farhad Hormozdiari, Can Alkan, Carles Vilà, Kevin Squire, Eli Geffen, Josip Kusak, Adam R. Boyko, Heidi G. Parker, Clarence Lee, Vasisht Tadigotla, Adam Siepel, Carlos D. Bustamante, Timothy T. Harkins, Stanley F. Nelson, Elaine A. Ostrander, Tomas Marques-Bonet, Robert K. Wayne, John Novembre. Genome Sequencing Highlights the Dynamic Early History of Dogs. PLoS Genetics, 2014; 10 (1): e1004016 DOI:10.1371/journal.pgen.1004016

Facebook Data Scientists Prove Memes Mutate And Adapt Like DNA (TechCrunch)

12/01/2014UncategorizedCibernética, Genética, Interatividade, Memes, Redes sociaisrenzotaddei

Posted Jan 8, 2014 by Josh Constine (@joshconstine)

Richard Dawkins likened memes to genes, but a new study by Facebook shows just how accurate that analogy is. Memes adapt to their surroundings in order to survive, just like organisms. Post a liberal meme saying no one should die for lack of healthcare, and conservatives will mutate it to say no one should die because Obamacare rations their healthcare. And nerds will make it about Star Wars.

Facebook’s data scientists used anonymized data to determine that “Just as certain genetic mutations can be advantageous in specific environments, meme mutations can be propagated differentially if the variant matches the subpopulation’s beliefs or culture.”

Take this meme:

“No one should die because they cannot afford health care, and no one should go broke because they get sick. If you agree, post this as your status for the rest of the day”.

In September 2009, 470,000 Facebook users posted this exact phrase as a status update. But a total of 1.14 million status updates containing 121,605 variants of the meme were spawned, such as “No one should be frozen in carbonite because they can’t pay Jabba The Hut”. Why? Because humans help bend memes to better fit their audience.

In the chart below you can see how people of different political leanings adapted the meme to fit their own views, and likely the views of people they’re friends with. As Facebook’s data scientists explain, “the original variant in support of Affordable Care Act (aka Obamacare) was propagated primarily by liberals, while those mentioning government and taxes slanted conservative. Sci-fi variants were slightly liberal, alcohol-related ones slightly conservative”. That matches theories by Dawkins and Malcom Gladwell.

1525321_10152134856908415_586555184_n

Average political bias (-2 being very liberal, +2 being very conservative) of users reposting different variants of the “no one should” meme.

As I wrote in my Stanford Cybersociology Master’s program research paper, memes are more shareable if they’re easy to remix. When a meme has a clear template with substitutable variables, people recognize how to put their own spin on it. They’re then more likely to share their own modified creations, which drives awareness of the original. When I recognized this back in 2009, I based my research on Lolcats and Soulja Boy, but more recently The Harlem Shake meme proved me right.

Facebook’s findings and my own have signficant implications for marketers or anyone looking to make a message go viral. Once you know memes are naturally inclined to mutate, and that these mutations increase sharing, you can try to purposefully structure your message in a remixable way. By creating and seeding a few variants of your own, you can crystallize how the template works and encourage your audience to make their own remixes.

As you can see in this graph from my research paper, usage of the word “haz” as in the Lolcat phrase “I can haz cheezburger” grew increasingly popular for several years. Meanwhile, less remixable memes often only create a spike in mentions for a few days. I posit that high remixability — or adaptability — keeps memes popular for a much longer period of time.

Screen Shot 2014-01-08 at 12.11.11 PM

Rise in mentions of the word “haz” in Facebook wall posts, indicating sustained popularity of the highly remixable Lolcats memes – as shown on the now defunct Facebook Lexicon tool

For social networks like Facebook, understanding how memes evolve could make sure we continue to see fresh content. Rather than showing us the exact copies of a meme over and over again in the News Feed, Facebook’s algorithms could purposefully search for and promote mutated variations.

That way instead of hearing about healthcare over and over, you might see that “No one should twerk just because they can’t avoid hearing Miley Cyrus on the radio. If you agree, sit perfectly still with your tongue safely inside your mouth for the rest of the day.”

Homem evolui mais devagar que macaco, diz estudo (Folha de S.Paulo)

25/10/2013UncategorizedEvolução, Evolucionismo, Genética, Macacosrenzotaddei

24 de outubro de 2013

Reportagem da Folha de SP mostra que pesquisa descobriu que diferenças entre espécies está em genes ativos

A comparação da atividade genética de humanos com a de chimpanzés sugere que o Homo sapiens está evoluindo de forma mais lenta que os macacos. A descoberta foi feita por cientistas que investigam por que o homem e seu primo mais próximo são tão diferentes, apesar de terem 98% do DNA idêntico.

O segredo das diferenças físicas e comportamentais está em quais genes são de fato ativos em cada espécie. Analisando células embrionárias, a brasileira Carolina Marchetto, do Instituto Salk, de San Diego (EUA), descobriu mecanismos que freiam a taxa de transformação genética da espécie humana.

A descoberta favorece a hipótese de que o advento da cultura desacelerou a evolução biológica: uma vez que humanos se adaptam a distintos ambientes usando o conhecimento, nossa espécie não depende mais tanto de variação genética para evoluir e sobreviver a mudanças.

Já os macacos, mamíferos de cognição mais limitada, precisam que seu DNA evolua de forma rápida para sobreviver a mudanças: eles não têm como compensar a falta de características inatas necessárias usando apenas conhecimento e tecnologia.

Mas o DNA humano também não carece de evoluir? “Não sabemos o que estamos pagando por isso em termos de adaptação, mas por enquanto funciona de forma eficiente”, diz Marchetto.

O trabalho da cientista, descrito hoje na revista “Nature”, ajuda a explicar o mistério da maior diversidade do DNA símio. Um leigo pode achar que todos os chimpanzés são iguais, mas uma só colônia selvagem desses macacos na África tem mais variabilidade genética do que toda a humanidade.

O PULO DO GENE

Segundo o estudo de Marcheto, a maior variabilidade genética dos macacos tem a ver com os chamados transpósons, genes que saltam de um lugar para outro dos cromossomos. Nesse processo, os transpósons reorganizam o genoma, ativando alguns genes e desativando outros.

Esses “genes saltadores” são bastante ativos em chimpanzés e bonobos (macacos igualmente próximos da linhagem humana). Em humanos, o transpóson é suprimido por dois outros genes que são ativados em abundância e inibem o “pulo” genético.

Chimpanzés, de certa forma, precisam de transpósons. Com ferramentas rudimentares e sem linguagem para transmitir conhecimento, eles têm de oferecer maior variabilidade genética à seleção natural para que ela os torne mais bem adaptados, caso o ambiente se altere.

A pesquisa de Marchetto só foi possível porque seu o laboratório no Salk, liderado pelo biólogo Fred Gage, domina a técnica de reverter células ao estágio embrionário.

O material usado na pesquisa foi extraído da pele de macacos e pessoas, pois há uma série de limitações para o uso de embriões em experimentos científicos.

Revertido ao estágio de “células pluripotentes induzidas”, o tecido cutâneo se comporta como embrião, e é possível investigar a biologia molecular dos estágios iniciais do desenvolvimento, quando o surgimento de diversidade genética tem consequências futuras.

“Uma das coisas especiais do nosso estudo é que a reprogramação de células de chimpanzés e bonobos nos dá um modelo para começar a estudar questões evolutivas que antes não tínhamos como abordar”, diz Marchetto.

RUMO AO CÉREBRO

As diferenças de ativação de genes entre humanos e chimpanzés, explica, não se restringem a células embrionárias. A ideia de Marcheto e de seus colegas agora é transformar essas células em neurônios, por exemplo, para entender como a biologia molecular de ambos se altera durante a formação do cérebro.

(Rafael Garcia/ Folha de São Paulo)

http://www1.folha.uol.com.br/ciencia/2013/10/1361208-homem-evolui-mais-devagar-que-macaco-diz-estudo.shtml

EUA vetam patente sobre gene humano (Folha de S.Paulo)

05/07/2013UncategorizedCapitalismo, Economia, Engenharia genética, Genética, Políticas públicas, Saúderenzotaddei

JC e-mail 4747, de 14 de Junho de 2013.

Suprema Corte decide que empresa não pode ter propriedade sobre genes usados em teste de risco de câncer. Decisão pode levar à redução no preço do exame, o mesmo feito por Angelina Jolie antes de retirada das mamas

A Suprema Corte dos EUA decidiu ontem que genes humanos não podem ser patenteados, o que pode afetar empresas de biotecnologia e baratear testes que se baseiam na procura de certas mutações no país e até no Brasil.

A decisão dos magistrados reverte três décadas de concessões de patentes pelo governo americano. No Brasil, não é permitido patentear seres vivos ou parte deles, o que inclui os genes.

O caso em discussão na Suprema Corte diz respeito ao registro de propriedade intelectual da empresa MyriadGenetics sobre os genes BRCA 1 e 2, cujas mutações indicam um risco maior de câncer de mama e ovário.

O teste que procura essas mutações ganhou maior notoriedade recentemente, depois que a atriz Angelina Jolie, 37, revelou, em junho, ter se submetido a uma cirurgia de retirada das mamas após descobrir ter as mutações que aumentam o risco de desenvolver um tumor.

O exame é recomendado principalmente para as mulheres que têm câncer antes dos 45 anos. É possível também rastrear a mutação em outros membros da família para decidir sobre medidas preventivas, que incluem o uso de remédios, o acompanhamento com exames de imagem e até retirada preventiva de mamas e ovários.

O preço do exame é uma barreira ao seu acesso. Nos EUA, o custo fica em torno de US$ 3.000; no Brasil, ainda que não haja o impedimento da patente, o preço também é alto, chegando a R$ 8.000.

Com a decisão, espera-se uma queda nesses valores. “O reflexo vai ser imediato aqui. As empresas se guiam pelo preço cobrado no exterior”, afirma Maria Isabel Achatz, diretora de oncogenética do A.C. Camargo Cancer Center, em São Paulo.

Para David Schlesinger, geneticista e fundador do laboratório Mendelics, a identificação de genes únicos, como no teste BRCA 1 e 2, já está ficando obsoleta.

“Em vez de procurar genes específicos, agora se sabe que é mais vantajoso fazer um exoma [sequenciamento da parte do genoma que codifica proteínas] e ter um panorama geral do paciente.”

BRECHA

Segundo a decisão, uma parte do DNA que ocorre naturalmente é um produto da natureza e não pode ser patenteado só por ter sido isolada pela empresa.

No entanto, o tribunal deu à Myriad uma vitória parcial, dizendo que o DNA complementar sintetizado em laboratório pode ser patenteado.

O chamado cDNA não acontece naturalmente. Grosso modo, é uma espécie de DNA que exclui as informações que não codificam proteína usada como parte do processo de desenvolvimento de alguns testes genéticos.

Os grupos que pedem o fim das patentes argumentam que a sequência dos nucleotídeos do cDNA segue a ordem imposta pela natureza e, por isso, não devem ser alvo de registros.

Para Fernando Soares, do Departamento de Patologia do A.C. Camargo Cancer Center, manter a patente do cDNA só deve ter impacto em questões de pesquisa e em análise de larga escala.

Envolvido no projeto do genoma do câncer, em 2002, o médico comemorou a decisão. “O genoma é um patrimônio da humanidade.”

Veja também o assunto no Jornal O Globo: Genes humanos não podem ser patenteados, decide Suprema Corte dos EUA. http://oglobo.globo.com/ciencia/genes-humanos-nao-podem-ser-patenteados-decide-suprema-corte-dos-eua-8676714

Schizophrenia Symptoms Eliminated in Animal Model (Science Daily)

23/05/2013UncategorizedAnimais, esquizofrenia, Genética, neurociências, Neurofisiologia, Saúde mentalrenzotaddei

May 22, 2013 — Overexpression of a gene associated with schizophrenia causes classic symptoms of the disorder that are reversed when gene expression returns to normal, scientists report.

Overexpression of a gene associated with schizophrenia causes classic symptoms of the disorder that are reversed when gene expression returns to normal, scientists report. Pictured are (left to right) Drs. Lin Mei, Dongmin Yin and Yongjun Chen, Medical College of Georgia at Georgia Regents University. (Credit: Phil Jones, Georgia Regents University Photographer)

They genetically engineered mice so they could turn up levels of neuregulin-1 to mimic high levels found in some patients then return levels to normal, said Dr. Lin Mei, Director of the Institute of Molecular Medicine and Genetics at the Medical College of Georgia at Georgia Regents University.

They found that when elevated, mice were hyperactive, couldn’t remember what they had just learned and couldn’t ignore distracting background or white noise. When they returned neuregulin-1 levels to normal in adult mice, the schizophrenia-like symptoms went away, said Mei, corresponding author of the study in the journal Neuron.

While schizophrenia is generally considered a developmental disease that surfaces in early adulthood, Mei and his colleagues found that even when they kept neuregulin-1 levels normal until adulthood, mice still exhibited schizophrenia-like symptoms once higher levels were expressed. Without intervention, they developed symptoms at about the same age humans do.

“This shows that high levels of neuregulin-1 are a cause of schizophrenia, at least in mice, because when you turn them down, the behavior deficit disappears,” Mei said. “Our data certainly suggests that we can treat this cause by bringing down excessive levels of neuregulin-1 or blocking its pathologic effects.”

Schizophrenia is a spectrum disorder with multiple causes — most of which are unknown — that tends to run in families, and high neuregulin-1 levels have been found in only a minority of patients. To reduce neuregulin-1 levels in those individuals likely would require development of small molecules that could, for example, block the gene’s signaling pathways, Mei said. Current therapies treat symptoms and generally focus on reducing the activity of two neurotransmitters since the bottom line is excessive communication between neurons.

The good news is it’s relatively easy to measure neuregulin-1 since blood levels appear to correlate well with brain levels. To genetically alter the mice, they put a copy of the neuregulin-1 gene into mouse DNA then, to make sure they could control the levels, they put in front of the DNA a binding protein for doxycycline, a stable analogue for the antibiotic tetracycline, which is infamous for staining the teeth of fetuses and babies.

The mice are born expressing high levels of neuregulin-1 and giving the antibiotic restores normal levels. “If you don’t feed the mice tetracycline, the neuregulin-1 levels are always high,” said Mei, noting that endogenous levels of the gene are not affected. High-levels of neuregulin-1 appear to activate the kinase LIMK1, impairing release of the neurotransmitter glutamate and normal behavior. The LIMK1 connection identifies another target for intervention, Mei said.

Neuregulin-1 is essential for heart development as well as formation of myelin, the insulation around nerves. It’s among about 100 schizophrenia-associated genes identified through genome-wide association studies and has remained a consistent susceptibility gene using numerous other methods for examining the genetics of the disease. It’s also implicated in cancer.

Mei and his colleagues were the first to show neuregulin-1’s positive impact in the developed brain, reporting in Neuron in 2007 that it and its receptor ErbB4 help maintain a healthy balance of excitement and inhibition by releasing GABA, a major inhibitory neurotransmitter, at the sight of inhibitory synapses, the communication paths between neurons. Years before, they showed the genes were also at excitatory synapses, where they also could quash activation. In 2009, the MCG researchers provided additional evidence of the role of neuregulin-1 in schizophrenia by selectively deleting the gene for its receptor, ErbB4 and creating another symptomatic mouse.

Schizophrenia affects about 1 percent of the population, causing hallucinations, depression and impaired thinking and social behavior. Babies born to mothers who develop a severe infection, such as influenza or pneumonia, during pregnancy have a significantly increased risk of schizophrenia.

Journal Reference:

Dong-Min Yin, Yong-Jun Chen, Yi-Sheng Lu, Jonathan C. Bean, Anupama Sathyamurthy, Chengyong Shen, Xihui Liu, Thiri W. Lin, Clifford A. Smith, Wen-Cheng Xiong, Lin Mei.Reversal of Behavioral Deficits and Synaptic Dysfunction in Mice Overexpressing Neuregulin 1.Neuron, 2013; 78 (4): 644 DOI:10.1016/j.neuron.2013.03.028

Cientistas americanos conseguem clonar embriões humanos (O Globo)

19/05/2013UncategorizedÉtica, Células tronco, ciência, Clonagem humana, Genética, Mediação tecnológicarenzotaddei

Trabalho é o primeiro a obter êxito em humanos com a técnica que deu origem à ovelha Dolly

Autores dizem que não se trata de fazer clones humanos, mas sim avançar apenas até a fase de blastocisto para obter as células-tronco

Em 2004, sul-coreano anunciou o mesmo feito mas foi desmentido um ano depois

ROBERTA JANSEN

Publicado:15/05/13 – 16h03; atualizado:15/05/13 – 20h56

Clone de embrião obtido no estudo Divulgação

OREGON. Dezesseis anos depois da clonagem do primeiro mamífero, a ovelha Dolly, cientistas conseguiram, pela primeira vez, clonar um embrião humano em seus primeiros estágios de desenvolvimento. Os protoembriões foram usados para produzir células-tronco embrionárias — capazes de se transformar em qualquer tecido do corpo —, num avanço bastante significativo e há muito tempo esperado para o tratamento de lesões e doenças graves como Parkinson, esclerose múltipla e problemas cardíacos. Especialistas envolvidos no processo garantem que o objetivo não é clonar seres humanos, mas, sim criar novas terapias personalizadas.

Tanto é assim que os embriões humanos clonados usados na pesquisa foram destruídos em estágios ainda muito iniciais de desenvolvimento, logo depois da extração das células-tronco, e não levados ao crescimento, como no caso da ovelha Dolly e de tantos outros animais clonados depois dela. A técnica usada, no entanto, foi bastante similar à que criou a ovelha. Células da pele de um indivíduo foram colocadas em um óvulo previamente esvaziado de seu material genético e estimuladas a se desenvolver. Quando atingiram a fase de blastocisto, as células-tronco embrionárias foram extraídas e os embriões destruídos. O estudo foi publicado na revista “Cell”.

Conseguir gerar grande quantidade de células-tronco do próprio paciente era uma espécie de Santo Graal da atual ciência médica, como comparou o jornalista Steve Connor, no “Independent”. Embora o procedimento tenha sido feito com animais, até agora nunca tinha sido obtido com material humano, a despeito de inúmeras tentativas. Aparentemente, a dificuldade viria da maior fragilidade do óvulo humano.

Em 2004, um grupo coordenado por Woo Suk Hwang, da Universidade Nacional de Seoul, anunciou ter produzido o primeiro embirão humano clonado e, em seguida, obtido células-tronco embionárias a partir dele. Menos de um ano depois, no entanto, o grupo, que já havia clonado um cachorro, foi acusado de fraude e desmentiu os resultados obtidos. Outros grupos tentaram, mas os embriões não passaram do estágio de 6 a 12 células.

A corrida pela obtenção das células-tronco embrionárias faz todo o sentido. Cultivadas em laboratório, essas células podem dar origem a qualquer tecido do corpo humano. Por isso, em tese ao menos, poderiam curar lesões na medula, recompor órgãos, tratar problemas graves de visão, oferecendo tratamentos inéditos para muitas doenças hoje incuráveis. Como os tecidos seriam feitos a partir do material genético do próprio paciente (que, no caso, cedeu as células de sua pele), não haveria risco algum de rejeição. A medicina personalizada alcançaria o seu ápice.

— Nossa descoberta oferece novas maneiras de gerar células-tronco embrionárias para pacientes com problemas em tecidos e órgãos — afirmou o coordenador do estudo, Shoukhrat Mitalipov, da Universidade de Ciência e Saúde do Oregon, nos EUA, em comunicado oficial sobre o estudo. — Essas células-tronco podem regenerar órgãos ou substituir tecidos danificados, levando à cura de doenças que hoje afetam milhões de pessoas.

O grupo também conseguiu observar a capacidade de diferenciação das células obtidas em tecidos específicos

— Um atento exame das células-tronco obtidas por meio desta técnica demonstrou sua capacidade de se converter, como qualquer célula-tronco embrionária normal, em diferentes tipos de células, entre elas, células nervosas, células do fígado e céluas cardíacas — disse Mitalipov, em entrevista ao “Independent”.

No entanto, o estudo já levanta sérias preocupações éticas, sobretudo em relação à criação de clones humanos. Há o temor de que a técnica seja incorporada às oferecidas por clínicas de fertilização in vitro, como alternativa para casais estéreis, por exemplo. Outros grupos argumentam que é simplesmente antiético manipular embriões humanos.

— A pesquisa tem como único objetivo gerar células-tronco embrionárias para tratar doenças graves; e não aumentar as chances de produzir bebês clonados — garantiu Mitalipov. — Este não é o nosso foco e não acreditamos que nossas descobertas sejam usadas por outros grupos como um avanço na clonagem humana reprodutiva.

Leia mais sobre esse assunto em http://oglobo.globo.com/ciencia/cientistas-americanos-conseguem-clonar-embrioes-humanos-8399684#ixzz2TlwDWsur © 1996 – 2013. Todos direitos reservados a Infoglobo Comunicação e Participações S.A. Este material não pode ser publicado, transmitido por broadcast, reescrito ou redistribuído sem autorização.

Uma (in)certa antropologia

An (un)certain anthropology

Arquivo da tag: Genética

Ancient viral molecules essential for human development (Science Daily)

‘Não podemos brincar de Deus com as alterações no genoma humano’, alerta ONU (ONU)

SBPC critica projeto sobre biodiversidade (Fapesp)

Huge epigenomic map examines life’s impact on our genes (New Scientist)

Alzheimer’s epigenetics

Cientistas publicam o primeiro atlas do epigenoma humano (O Globo)

Dados sobre processos que afetam células, responsáveis por sua diferenciação em 111 dos tecidos do corpo, podem ajudar na melhor compreensão de diversas doenças e no desenvolvimento de novos tratamentos para elas

Epigenética na agricultura é tema de livro (Facesp)

Do viruses make us smarter? (Science Daily)

Cientistas descobrem dois genes relacionados a crimes violentos (Zero Hora)

How learning to talk is in the genes (Science Daily)

The original Eskimos have no living descendants, say scientists (The Christian Science Monitor)

US Scientists, Oil Giant Stole Indigenous Blood (Common Dreams)

What gave us the advantage over extinct types of humans? (The Hebrew University of Jerusalem)

Genetic study tackles mystery of slow plant domestications (Science Daily)

Revolução neandertal (Folha de S.Paulo)

A challenge to the genetic interpretation of biology (University of Eastern Finland)

Modelo pode ajudar a prever como espécies da Mata Atlântica responderão às mudanças climáticas (Fapesp)

New application of physics tools used in biology (Science Daily)

Humanity’s forgotten return to Africa revealed in DNA (New Scientist)

Ancient lineages

Khoe-Kwadi tribes

Twist in tale

Back to Africa – but from where?

Neanderthals Leave Their Mark on Us (New York Times)

Genomes of Modern Dogs and Wolves Provide New Insights On Domestication (Science Daily)

Facebook Data Scientists Prove Memes Mutate And Adapt Like DNA (TechCrunch)

Homem evolui mais devagar que macaco, diz estudo (Folha de S.Paulo)

EUA vetam patente sobre gene humano (Folha de S.Paulo)

Schizophrenia Symptoms Eliminated in Animal Model (Science Daily)

Cientistas americanos conseguem clonar embriões humanos (O Globo)