HNF4A and diabetes mellitus: The hepatocyte nuclear transcription factors, HNF1A and HNF4A, play crucial roles in glucose-stimulated insulin secretion as evidenced by the identification of loss-of- function variants in these genes in individuals with maturity-onset diabetes of the young (MODY)(OMIM #125850), an autosomal dominant form of diabetes typically diagnosed before the age of 25 years [40].