Some genes like it hot

Regional DNA differences may be due to climate

WASHINGTON — You are where you live, scientists who study genetic variations among people from different geographic regions are finding. For example, people who live in locations that get lots of solar radiation are more likely to have a sweat gland gene variant that may help them cool off more efficiently, geneticist Anna Di Rienzo of the University of Chicago reported February 19 at the annual meeting of the American Association for the Advancement of Science.

Humans have settled across the globe, contending with vastly different landscapes, heat, UV radiation levels, food types and pathogens. By sorting through loads of genetic data from around the globe, Di Rienzo and her colleagues found that one version of a gene that produces a protein found in sweat glands is more common among people living in hot, sunny locales.

All sorts of things can influence the genome, says Peter Zimmerman of Case Western Reserve University School of Medicine in Cleveland: “It’s environmental effects, and exposure to different food, different diseases, and different amount of sunlight.”

The team divided up the world’s regions, classifying them by factors such as polar, dry, tropical and humid. They also sorted out how inhabitants got their food, including data such as whether they were farmers or foragers and what they ate. A variant of a gene called keratin 77, which has a role in the sweat gland, was associated with locations that get high levels of solar radiation in the summer.

The study also found many other gene variants that are tied to climatic gradients such as precipitation. This approach is different from other ways that researchers look for gene-environment associations because it allows environmental categories to guide researchers’ predictions about what the gene variants do, rather than taking a more “agnostic” view that ignores the ways that different habitats can influence the prevalence of certain genes, Di Rienzo says.

These kinds of studies can focus researchers’ efforts on important genes, says anthropologist Cynthia Beall of Case Western Reserve University. “You’d know where to go, at least.”

Zimmerman says that while it’s true the environment can sculpt the human genome, its effects are likely to come at a glacial pace. “How rapidly the human genome responds to change, I would say it’s going to be slow. Our generation time is not fast.” 

Di Rienzo is using the same method to pinpoint genetic changes that might have a role in the various disease rates found among different populations. “We know for sure that a lot of these differences are due to environmental risk factors that differ,” she says. “But there’s also a growing consensus that genetic factors may also contribute to these differences in disease or trait prevalence.”

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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