MafB is a member of the Maf basic leucine-zipper containing transcription factor family. MafB is an islet-enriched protein that plays a role in beta cell-specific and glucose-responsive insulin gene transcription. MafB is expressed in all developing insulin and glucagon producing cells but is restricted to alpha cells in adults. MafB is has been shown to be critical for alpha and beta cell differentiation. Alternative names for MafB include v-maf musculoaponeurotic fibrosarcoma oncogene homolog B, transcription factor Maf1, segmentation protein KR, kreisler, Krml, Krml1, kr, and Maf1.