Genetics of Diabetes and Diabetic Complications

Diabetes is a collection of diseases characterized by defective glucose homeostasis. Different diabetes types have different etiologies and their genetic architecture ranges from highly penetrant monogenetic diseases, such as MODY and neonatal diabetes, to polygenic diseases, such as type 1 and type 2 diabetes that are caused by numerous genetic variants adding up to the individual risk. While both diabetes and diabetic complications have been known to be partly heritable for a long time, identification of risk variants was originally limited to a few variants with relatively modest effect sizes. This changed with the advent of genome-wide association studies (GWAS), which has led to the identification of hundreds of common risk variants for diabetes. Still, these variants only explain part of the heritability of complex diabetes types. Further technical development in the field, such as next-generation sequencing, has recently enabled identification of rare variants. Epigenetics, epistasis, gene-environment interactions, parent-of-origin effects, and noncoding RNAs are current research areas that provide additional layers to the genetic architecture and might reveal some of the missing heritability. In this chapter, we review the genetic basis of different diabetes types and diabetic complications and the major methodological milestones that have enabled the many success stories of the last decade.