Heterozygous mutations in the HNF1B gene are the cause of a complex human syndrome known as renal cysts and diabetes (RCAD; OMIM #137920), characterized by early onset of diabetes and developmental abnormalities of the kidney, genital tract and pancreas, as well as a variety of renal, liver, pancreas and biliary dysfunctions (Clissold et al., 2015; Barbacci et al., 2004; Bellanné-Chantelot et al., 2004, 2005; Haldorsen et al., 2008; Haumaitre et al., 2006; Kettunen et al., 2017; Lindner et al., 1999). Here, HNF1B is linked to diabetes mellitus.