Knowing now that P2-HNF4α is expressed in the adult liver under certain conditions of stress – including fasting and type 2 diabetes – raises the possibility that the effects of the MODY1 mutations in the P2 promoter could be due, at least in part, to an inability to express P2-HNF4α in the liver under key conditions (Da 83). Here, HNF4A is linked to type 2 diabetes mellitus.