Melanophore and fluoroleucophore synergistically photo-protect the Arabian killifish, Aphanius dispar, embryo from ultraviolet light

Abstract Pigment cells in fish species play crucial roles in forming colour patterns of each species and other physiological characteristics including photoprotection. Research on photoprotection by pigment cells in animals has primarily concentrated on black pigment cells, known as melanophores. However, the roles of other pigment cells and their synergistic effects on UV protection remain poorly understood. In this study, we use the Arabian killifish embryos as a model for studying the mechanisms of UV protection by different pigment cells. This species features highly fluorescent pigment cells called fluoroleucophores and black pigment cells known as melanophores. The fluorescent pigments and black melanin pigments are generated by genes gch (GTP cyclohydrolase) and tyr (tyrosinase) respectively. We generated gch(-/-) and gch/tyr(-/-) double mutant lines using CRISPR/Cas9 genome editing and examined the UV sensitivity of these mutant embryos. Both morphology and gene expression data revealed that the gch/tyr(-/-) double mutant line exhibited the highest UV sensitivity, and the gch(-/-) line also demonstrated a greater stress response compared to wild type (WT). From the study, we have identified the synergistic role of black and fluorescent pigment cells in providing effective UV protection from the early stages of embryonic development.