In a recent study published in the journal Nature Genetics, a multi-site team of researchers conducted the first genetic study of inflammatory bowel disease (IBD) including individuals from varied populations, revealing that the regions of the genome underlying the disease are similar around the world.
The study supported by the International IBD Genetics Consortium and titled “Association analyses identify 38 susceptibility loci for inflammatory bowel disease and highlight shared genetic risk across populations” involved a total of 10,000 DNA samples from Indian, Iranian and East Asian descents and 86,640 DNA samples from individuals across North America, Oceania and Europe.
Evidence shows that if the genetic effects on the risk of the disease are consistent across different populations indicates, then the biological cause of the disease is also consistent, which could have important implications for the development of treatments for IBD.
“The prevalence of IBD has increased dramatically in Asia over the last 50 years, probably due to lifestyle changes brought about by economic growth,” said Dr. Carl Anderson, a corresponding author from the Wellcome Trust Sanger Institute. “We are now able to compare genetic risk profiles of IBD across diverse populations to find out how similar they are. Discovering differences can provide us with biological insights that would be missed if we were to focus our efforts on just a single population. In turn, this can lead to the identification of new drug targets.”
“In our study, we found little difference in the genetic risk of IBD across the populations we studied. This is a very important finding because it suggests that biological lessons learned by studying the genetics of IBD will be relevant globally.”
The increased risk of IBD has been associated with over 163 human genome variants, however, this type of analysis has only been conducted at a large scale in European individuals.
By adding to the existing European samples, 10,000 non-European DNA samples, the researchers discovered 38 other genomic regions that influence the proneness to develop IBD. Since the genetic effects were consistent across all studied populations, the team believes that the discovery of these new regions were related to the increase in the sample size.
“We’ve already seen the benefit of using trans-ethnic approaches to understand complex diseases such as type 2 diabetes and rheumatoid arthritis,” said Dr. Jimmy Liu, a first author from the Sanger Institute. “This study demonstrates the importance of collecting trans-ethnic data on IBD, firstly because any increase in the number of samples improves our ability identify regions of the genome influencing disease risk, and secondly because we can gain new insights into the biology underlying IBD by comparing results across the diverse populations.”
Results from the study showed that there are specific genetic differences between the risk of IBD between European and non-Europeans, such as variants in the gene NOD2, which was found in the study to increase the risk of IBD in Europeans, and to be absent in Asians.
The gene TNFSF15 was found in the study to increase the risk of IBD at a similar frequency in East Asians and Europeans, however, the results showed that they have a more robust effect in East Asians, with the researchers indicating that this results may be due environment differences or the structure of the genome.
“This study is testimony to the need for large-scale international collaborations that enable us to answer questions that would not be possible using samples drawn from a single population,” said Dr. Rinse K Weersma, a corresponding author from University Medical Center Groningen. “We thank every individual who donated a DNA sample to the study and the clinicians within the International IBD Genetics Consortium who collected these, particularly those outside of the US and Europe. The finding that the biology underlying IBD is consistent across populations is hugely important, it tells us that we can use insights from genetic studies of IBD to develop globally relevant drugs with the potential to improve disease management around the world.”