HNF1A and maturity-onset diabetes of the young type 3: Though classified under the same subtype, more than 200 different heterozygous mutations in the hepatocyte nuclear factor 1α (HNF1α) gene have been associated with MODY3 (Bellanne-Chantelot et al., 2008; Ellard and Colclough, 2006; Frayling et al., 1997; Yamagata et al., 1996).