Question

Are there specific genes associated with Type I diabetes? If so, which specific genes are associated with which ethnicities?

I found that the HLA genes on chromosome 6 increase the risk of getting type 2 diabetes but was having a little more trouble with the second part of the question.

Answer 1

The first thing that you have to known is that type I diabetes is a polygenic disease which means that the phenotypic traits are determined by genetic factors in which several genes intervene and which are also influenced by environmental factors modifying these traits.

Even if type 1 diabetes is a polygenic disease, the genes of the HLA region, especially the HLA genes Class II such as DQA1, DQB1 and DRB1 are the main genetic susceptibility factors against the disease. The HLA region is located on the short arm of chromosome 6 in a region that covers about 4,000 Kbp which contains more than 200 genes, of which 40% are estimated to be related to immune function.

The incidence rate of type 1 diabetes varies greatly in different countries and ethnic groups. Several studies have observed that people from the Italian island of Sardinia (a genetically conserved population that shows a high incidence rate of the disease) and who migrated to continental Italy (with a low incidence rate), kept the incidence rates from its place of origin, which would indicate the important effect of genetics on the risk of developing diabetes. Another study in populations of Germany reached the same conclusion. There is a close correlation between the prevalence of genetic risk markers HLA with the incidence rate of the disease in European countries

In these studies, It has been observed that 90% of the patients with cardiovascular disease (related to diabetes) carries the HLA-DQ2 molecule which is encoded by the haplotype HLA-DQA1-DQB1.

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