HNF4A and type 2 diabetes mellitus: The most frequently affected maturity-onset diabetes of the young (MODY) genes include the enzyme glucokinase (GCK, MODY2) (86, 87) and the transcription factor genes hepatic nuclear factor 1 alpha (HNF1A, MODY3) (88), hepatic nuclear factor 4 alpha (HNF4A, MODY1) (89), and hepatic nuclear factor 1 beta (HNF1B, MODY5) (90).