18] Cultured amphibian melanophores: a model system to study melanopsin photobiology

Abstract

Publisher Summary Melanopsin is expressed by scattered perikarya among the amacrine and ganglion cells of the primate retina. In amphibians, melanopsin is expressed in the retina, hypothalamus, iridial myocytes, and melanophores. Amphibian melanophore responses to light protect vital organs against ultraviolet irradiation and produce rapid color changes needed for camouflage responses and animal survival. From a technical standpoint, it is important to understand the regulation and expression of melanopsin to avoid misinterpreting the actions of other agents on amphibian melanophores studied in lighted environments. This chapter describes the Xenopus melanophore model system. It also describes methods for monitoring the effects of melanopsin gene overexpression on the photobiological response of cultured transgenic melanophores. As computerized image analysis techniques for easy and reliable automated measurement of pigment dispersion are developed, it is anticipated that assay technologies in the melanophore model system will become more sophisticated. Future transgenic studies are likely to use Xenopus tropicalis instead of Xenopus laevis as a melanophore source to avoid the complications of pseudotetraploidy.