Pigment pattern formation by contact-dependent depolarization.

Although recent experimental studies have suggested that the interactions among the pigment cells play a key role in the skin pattern formation, details of the mechanism remain largely unknown. By using an in vitro cell culture system, we have detected interactions between the two pigment cell types, melanophores and xanthophores, in the zebrafish skin. During primary culture, the melanophore membrane transiently depolarizes when contacted with the dendrites of a xanthophore. This depolarization triggers melanophore migration to avoid further contact with the xanthophores. Cell depolarization and repulsive movement were not observed in pigment cells with the jaguar mutant, which shows defective segregation of melanophores and xanthophores. The depolarization-repulsion of wild-type pigment cells may explain the pigment cell behaviors generating the stripe pattern of zebrafish.