A new study has found that living in a city can influence the expression of your genes.

The findings, published in Sunday's online issue of Nature Genetics, are further evidence that our environment and lifestyle play a key role in our genetics.

For the study researchers recruited 200 Moroccan individuals from two ethnic groups — Arab and Berber — said geneticist and supervising author Greg Gibson of Georgia Tech in the U.S.

'The underlying hypothesis is that there would be more exposure to things like infectious diseases [for people living in high density cities] because it spreads more easily.'— Peter Visscher

"The Amazigh Berbers are descendants of the first modern humans who populated north Africa 35,000 years ago. The Arabs moved into southern Morocco between the seventh and 11th centuries," write the authors.

Gibson says many of the Amazigh and Arabic people in Morocco live in villages, but some have relocated to cities.

The aim of the research, says Gibson, was to examine both populations and determine the effect of "nature, nurture and culture on human physiology."

He says the environment includes "the complex mix of what you eat, how stressed you are and where you live."

For the study, blood samples were taken from individuals living in both the city and villages.

There has been a lot of research on gene expression in an experimental setting, but that only shows an artificial effect of the environment, said statistical geneticist and co-author Peter Visscher of the Queensland Institute of Medical Research.

Natural setting

Visscher and his colleague's study was designed to examine the gene expression of those living in the city, in high density areas, compared with those people living in villages.

"The underlying hypothesis is that there would be more exposure to things like infectious diseases [for people living in high density cities] because it spreads more easily," Visscher said.

He said researchers found two classes of genes, which are known to have roles in viral infection and renal health, that were expressed very differently in people living in the city compared to those living in villages.

Overall, the study found "gene expression differed between the two locations in up to a third of all transcripts," Visscher said.

"The main conclusions showed that, which genes are expressed and how much of each gene is expressed depends primarily on where you live and what lifestyle you live."

He said they then used genome-wide association studies, which can link specific traits or disease conditions to specific gene regions, to assess to what extent genetics determines gene expression.

Environmental context of disease susceptibility

If you look at a group of people who have similar lifestyles or live in the same region, a lot of the gene expression variations are genetic because the major environmental differences no longer exist, Visscher said.

"If we are going to think about [people's] disease susceptibility, it's not enough just to look at the genotype. We need to consider those in the context of the environment," says Gibson.

Gibson says the research team is now studying a wide range of population groups to further assess the effect the environment has on gene expression.