Humans with a monogenetic form of diabetes, referred to as maturity onset diabetes of the young 5 (MODY 5) (Horikawa et al., 1997), are mutant in HNF1B. A previous study identified Hnf1β as a downstream target for RA in the context of zebrafish pancreas development (Song et al., 2007). This evidence concerns the gene HNF1B and diabetes mellitus.