A Pomc (pro-opiomelanocortin-alpha) (bacterial artificial chromosome; RPCI22-372J15) was used to generate mice expressing cre under the control of the Pomc promoter. The cre recombinase cDNA was inserted via homologous recombination into the first ATG transcription start site, ablating the first 30bp of the POMC coding sequence. This transgenic vector was introduced to FVB-derived embryos.