This suggests that not only is PAX6 essential for pancreatic endocrine maintenance, but that correct dosage of the protein is required for this role, as it is for some other transcription factors associated with diabetes, such as HNF1A and HNF4A, in which heterozygous mutations have been found in a significant portion of MODY cases [35]. The gene discussed is HNF4A; the disease is diabetes mellitus.