An orthologue of the kit-related gene fms is required for development of neural crest-derived xanthophores and a subpopulation of adult melanocytes in the zebrafish, Danio rerio

Developmental mechanisms underlying traits expressed in larval and adult ve rtebrates remain largely unknown. Pigment patterns of fishes provide an opp ortunity to identify genes and cell behaviors required for postembryonic mo rphogenesis and differentiation. In the zebrafish, Danio rerio, pigment pat terns reflect the spatial arrangements of three classes of neural crest-der ived pigment cells: black melanocytes, yellow xanthophores and silver irido phores. We show that the D. rerio pigment pattern mutant panther ablates xa nthophores in embryos and adults and has defects in the development of the adult pattern of melanocyte stripes. We find that panther corresponds to an orthologue of the c-fms gene, which encodes a type III receptor tyrosine k inase and is the closest known homologue of the previously identified pigme nt pattern gene, kit. In mouse, fms is essential for the development of mac rophage and osteoclast lineages and has not been implicated in neural crest or pigment cell development. In contrast, our analyses demonstrate that fm s is expressed and required by D. rerio xanthophore precursors and that fin s promotes the normal patterning of melanocyte death and migration during a dult stripe formation. Finally, we show that fms is required for the appear ance of a late developing, kit-independent subpopulation of adult melanocyt es. These findings reveal an unexpected role for fms in pigment pattern dev elopment and demonstrate that parallel neural crest-derived pigment cell po pulations depend on the activities of two essentially paralogous genes, kit and fms.