HNF4α is a member of the HNF4 orphan subfamily of the nuclear receptor superfamily of transcription factors that is required for hepatocyte differentiation and development of the liver. It has been shown to constitutively bind fatty acids. HNF4α is almost exclusively expressed in the gastrointestinal system (stomach, duodenum, jejunum, ileum, colon, and gall bladder), liver and kidney, with lower levels in white adipose tissue and pancreas. HNF4α dysfunction has been implicated in mature onset diabetes of the young, (MODY), type I, type II diabetes mellitus, high serum lipid levels, chronic kidney failure and metabolic syndrome. Targeted disruption (knockout) of HNF4α results in defects in embryonic development, homeostasis and metabolism, the liver and biliary system and the central nervous system (CNS).