Genetic factors in the etiology of type 2 diabetes: linkage analyses, candidate gene association, and genome-wide association – still a long way to go! -

Type 2 diabetes is a complex and pleomorphic metabolic disorder arising from a complex interaction between genes and the environment. During the last decade there has been an outpouring of studies providing clues into the genetic architecture underlying type 2 diabetes mellitus. This review provides an overview of the genetics of type 2 diabetes in the context of recent progress in the understanding of the genetic susceptibility of the disease. Approximately 40 variants have been identified so far and the identification of these susceptibility loci for diabetes has introduced novel genes, pathways and mechanisms of diabetes pathogenesis. The genetic loci so far identified account for only a small fraction (approximately 10%) of the overall heritable risk for type 2 diabetes mellitus. Uncovering the missing heritability is essential to the progress of type 2 diabetes genetic studies and to the translation of genetic information into clinical practice. However, it may be a long time before all the susceptibility genes are found. It may take even more time before their roles in different pathways have been elucidated and the mechanisms involved in their interaction with other factors in the disease etiology clarified.