Research advances of iridophores in Teleosts

The iridophore is a kind of common pigment cell in teleosts. It contains a large number of iridosomes, which contain reflecting platelets with high refractive index composed of guanine crystals. The reflecting platelets and the cytoplasm with low refractive index are alternately arranged to form alternating layers. After light is reflected by the alternating layers, the iridophores show an iridescent color through multilayer thin-film interference. Iridophores achieve color change by changing the distances between each of the reflecting platelets under the stimulation of hormones, sympathetic nervous system or external environment factors. Guanine is the basis for the coloration and color changes of iridophores, and its biosynthesis pathway has been analyzed in detail. Iridophores are differentiated from multipotent neural crest cells. The lineage specialization process of differentiation from neural crest cells to mature iridophores requires multiple genes. At present, some key genes have been found in the model organism, zebrafish, and the core gene regulatory network governing iridophore specification has been preliminarily analyzed through studying the interactions among those genes. At the same time, other genes and signaling pathways affecting the specialization, differentiation and survival of iridophores have also been found. This manuscript reviews advances of studies in the mechanism of coloration and color change of iridophores, the pathway and genes involved in guanine biosynthesis, as well as genes and signaling pathways affecting the development and survival of iridophores in teleosts. Prospects for future research directions are also provided. It is aimed at a deeper understanding of iridophores and providing a reference for studying gene regulation during iridophore development.