Scientists identify 111 new genetic locations that indicate susceptibility to type 2 diabetes.
Type 2 diabetes affects hundreds of millions of people worldwide, and the numbers have skyrocketed in recent years. According to the World Health Organization (WHO), the number of people with diabetes has almost quadrupled in the past few decades, from 108 million in 1980 to 422 million in 2014.
In the United States, 29 million people currently have diabetes, and 86 million are thought to have prediabetes.
Until now, researchers were aware of 76 chromosomal locations, or "loci," that underlie this metabolic disease. However, new research analyzed the human genome further and found an additional 111.
The new study - published in the American Journal of Human Genetics - was co-led by Dr. Nikolas Maniatis of University College London's (UCL) Genetics, Evolution, and Environment department, together with Dr. Toby Andrew of Imperial College London's Department of Genomics of Common Disease.
Identifying the type 2 diabetes genetic loci
Using a UCL-developed method of genetic mapping, Maniatis and team examined large samples of European and African American people, summarizing 5,800 cases of type 2 diabetes and almost 9,700 healthy controls.
They found that the new loci - together with the ones previously identified - control the expression of more than 266 genes surrounding the genetic location of the disease.
Most of the newly discovered loci were found outside of the coding regions of these genes, but within so-called hotspots that change the expression of these genes in body fat.
Of the newly identified 111 loci, 93 (or 84 percent) were found in both European and African American population samples.
After identifying genetic loci, the next step was to use deep sequence analysis to try to determine the genetic mutations responsible for the disease.
Gene mapping finds areas associated with diabetes-causing genetic loci
Maniatis and colleagues used deep sequencing to further examine three of the cross-population loci with the aim of identifying the genetic mutations. They then investigated a different sample of 94 Europeans with type 2 diabetes, as well as 94 healthy controls.
The researches found that the three loci coincided with chromosomal regions that regulate gene expression, contain epigenetic markers, and present genetic mutations that have been suggested to cause type 2 diabetes.
Dr. Winston Lau, of UCL's Genetics, Evolution, and Environment department, explains the significance of these findings:
"Our results mean that we can now target the remaining loci on the genetic maps with deep sequencing to try and find the causal mutations within them. We are also very excited that most of the identified disease loci appear to confer risk of disease in diverse populations such as African Americans, implying our findings are likely to be universally applicable and not just confined to Europeans."
Dr. Maniatis also highlights the contribution their study brings to the research community:
"No disease with a genetic predisposition has been more intensely investigated than type 2 diabetes. We have proven the benefits of gene mapping to identify hundreds of locations where causal mutations might be across many populations, including African Americans. This provides a larger number of characterized loci for scientists to study and will allow us to build a more detailed picture of the genetic architecture of type 2 diabetes," says the lead author.
Dr. Andrew also adds, "Before we can conduct the functional studies required in order to better understand the molecular basis of this disease, we first need to identify as many plausible candidate loci as possible. Genetic maps are key to this task, by integrating the cross-platform genomic data in a biologically meaningful way."