Duplicated Tyr disruption using CRISPR/Cas9 reveals melanophore formation in Oujiang color common carp (Cyprinus carpio var. color)

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Gene duplication plays an important role in the regulation of biological traits. The Tyr inactivation have been confirmed to hinder melanin synthesis, but the research of duplicated Tyr function and evolution in fish, especially in ornamental farm fish, is insufficient. To test whether the duplicated Tyr has effect on black patches formation in Oujiang color common carp (Cyprinus carpio var. color), we obtained duplicated Tyr gene (Tyr1 and Tyr2), each of them possesses biased expression in melanocyte-rich skin, indicating existence of function. The various mutants by disrupting Tyr in white-black (WB) types of Oujiang color common carp using the CRISPR/Cas9 tool were generated. The Tyr2 mosaic mutant WB exhibited shallow black patches, while simultaneously disrupting two Tyr genes caused different levels of melanin loss in the eyes and on black patches. Most obviously, the complete albino individuals were obtained with non-wild type sequence and distinguished from whole white (WW) in the pigmentation of eyes. The correlation analysis between the gene mutation type and phenotype revealed that duplicated Tyr were co-involved in melanogenesis, where Tyr1 was the key factor, and Tyr2 might have been playing compensatory roles on the melanin synthesis in Oujiang color common carp. Our study provided insight into regulation mechanism of black patches formation in fish and breeding of special traits in future.