Category Archives: Transhuman News

Hold the butter! The genetic secrets of centenarians are starting to be unravelled and they hint that low cholesterol plays a role in their unusual longevity.

"This is one of the first studies to detect rare genotypes in these exceptional individuals," says Joo Pedro de Magalhes of the University of Liverpool, UK, who was not involved in the research.

It is thought that genetics accounts for up to 30 per cent of the variability in human lifespan. But so far just two genes have been linked to longevity, and neither has a large influence creating a genetic puzzle sometimes called "missing heritability".

Suspicion has been growing that rare mutations are behind longevity. But these get missed by standard genetic studies, which sequence small snippets of DNA for known variants rather than scouring the full genome to find unknown ones.

To look for unknown rare mutations, Timothy Cash of the Spanish National Cancer Research Centre in Madrid and his colleagues sequenced the entire exome the protein-coding part of DNA of three Spanish centenarians and four of their long-lived siblings. These were compared with the exomes of 800 people, many of whom could be assumed to have average lifespans, as only one in 5000 people live to 100.

One gene apolipoprotein B had rare mutations in all three long-lived families that were less common in the 800 controls. The protein made by this gene helps carry "bad cholesterol" in the blood, high levels of which lead to heart attacks. It is possible that the mutations reduce levels of this bad cholesterol.

The team is now investigating whether the centenarians' cholesterol levels bear out this theory. If they do, "this would definitely reinforce the idea that cardiovascular health is an important factor in overall ageing", says Cash.

Intriguingly, previous work has shown that another gene for which there is strong evidence for a role in human lifespan is apolipoprotein E, which also helps transport cholesterol. However, the beneficial variants of this gene also reduce the risk of Alzheimer's disease, which is usually thought to be the main reason behind their effects on longevity.

Another gene that has recently been implicated in longevity is FOXO3A, which may affect people's sensitivity to insulin.

Journal reference: Aging Cell, doi.org/vfv

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Gene variant found that may help people live to be 100

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A new study calls into question the evolutionary stability of an ecological explanation of biodiversity.

The study, published in the journal PLOS ONE, brings together evolutionary theory and ecology to explore one of the big questions in ecology: How is biodiversity developed and maintained?

"This is a fundamental question if we want to protect biodiversitywhat exactly do we need to protect?" says IIASA Evolution and Ecology Program Director Ulf Dieckmann, who led the study together with Florian Hartig from the University of Freiburg, collaborating with colleagues from the Helmholtz Centre for Environmental Research in Leipzig and the French National Center for Scientific Research in Grenoble.

In Biology 101, students learn that two species cannot occupy the same niche, and that the world's biodiversity is thus closely related to the number of niches that exist. But in fact, in the real world this is often not trueit appears that organisms can and do occupy the same niche, meaning that they feed on the same resource, in the same place, at the same time.

"For example," says Dieckmann, "herring and sprat in the Baltic Sea occupy very similar ecological niches, feeding on the same kinds of plankton. How such species can robustly co-exist is a key question for modern ecology."

One theory, known as Relative Nonlinearity of Competition (RNC), suggests that such species can co-exist because they react differently to fluctuations in resources or other limiting factorssuch as algal blooms for fish, or rainfall variations for mosquitoescausing changes in the environment that temporarily benefit the other species. This leads to a dynamic relationship in which each species temporarily benefits from the other's influence on the environment, holding the two in balance.

"The idea has held up well in theory, but it's difficult to test in practice," says Dieckmann. So he and his colleagues decided to test RNC from another perspective, using three standard evolutionary models. "We wanted to find out what happens to the RNC mechanism when we allow the species to adapt."

Their results show that RNC is typically not stable if one considers evolution: in all three models, the species differences that supported their coexistence disappear through adaptation. This means that, evolutionarily, the two coexisting species are outcompeted and replaced by a single species. Dieckmann says, "We thus suggest that the potential of this mechanism for explaining the origin and maintenance of biodiversity might have been overestimated in the literature."

The scientists conclude that further research will be needed to understand what other mechanisms support biodiversity.

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Biodiversity in the balance