PDX1 and diabetes mellitus: Six genes account for the majority of the monogenic forms of diabetes: hepatic nuclear factor 4α (HNF-4α), glucokinase (GCK), hepatic nuclear factor 1α (HNF-1α), insulin promoter factor-1 (IPF-1), hepatic nuclear factor 1β (HNF-1β) and neuro D1 transcription factor (NEUROD1) [40].