However, heterozygous mutations in the GCK (glucokinase) (MODY 2), HNF1A (hepatocyte nuclear factor 1 alpha) (MODY 3), and HNF4A (hepatocyte nuclear factor 4 alpha) (MODY 1) genes are the most frequent, and together they explain over 95% of the known genetic causes of MODY [6]. The gene discussed is HNF4A; the disease is MODY.