A study of twins may lead to better understanding whether genes play a role in what kind of gut microbes a person has, and if this interplay influences such conditions as Crohn's disease, obesity and diabetes.

"Despite the importance of both variation in the human genome and variation in the gut microbiome to human health, there is currently little knowledge connecting the two," said Ruth Ley, Cornell assistant professor of microbiology, and principal investigator of a new $1.72 million grant from the National Institute of Diabetes and Digestive and Kidney Diseases, which is part of the National Institutes of Health (NIH).

Ley and colleagues will first establish healthy baselines using genotyping data of 8,000 identical and fraternal twins, whose genomes have been sequenced at King's College in London and are stored in their "TwinsUK" registry.

They plan to line up the genetic sequences of each pair of twins and see where there are similarities and genetic variation between siblings. At the same time, each of the 8,000 participants will submit a fecal sample for gut biota analysis.

The scientists will then try to predict, based on the degree to which sets of twins share genes in common, whether certain genes might be influencing abundances of gut microbes.

"One of the questions we'll be asking is when fraternal twins share genes in common, do they also share microbiota? And by comparing the gut microbiota of identical twins, that have identical genomes, we will gain a better understanding of how environmental factors shape gut microbial ecology," said Ley. Answers to such questions may help distinguish between the roles that genes, lifestyles and environments play in the composition of gut bacteria.

Though very little prior work exists, the researchers suspect that immune system genes and genes related to how food is processed may play roles in microbe abundances and disease.

In the research process, Ley and colleagues also may "may pick up gene variants implicated in diseases," she added.

Ley received a pilot grant of $20,000 from the Cornell Center for Comparative and Population Genomics that allowed her to survey 100 people, which was critical in her application for the NIH grant.

Co-investigators of the new grant include Andy Clark, Cornell professor of population genetics, and Tim Spector, a professor of epidemiology at King's College.