Nile Tilapia: A Model for Studying Teleost Color Patterns

Abstract

The diverse color patterns of cichlid fishes play an important role in mate choice and speciation. Here we develop the Nile tilapia (Oreochromis niloticus) as a model system for studying the developmental genetics of cichlid color patterns. We identified 4 types of pigment cells: melanophores, xanthophores, iridophores and erythrophores, and characterized their first appearance in wild-type fish. We mutated 25 genes involved in melanogenesis, pteridine metabolism, and the carotenoid absorption and cleavage pathways. Among the 25 mutated genes, 13 genes had a phenotype in both the F0 and F2 generations. None of F1 heterozygotes had phenotype. By comparing the color pattern of our mutants with that of red tilapia (Oreochromis spp), a natural mutant produced during hybridization of tilapia species, we found that the pigmentation of the body and eye is controlled by different genes. Previously studied genes like mitf, kita/kitlga, pmel, tyrb, hps4, gch2, csf1ra, pax7b, and bco2b were proved to be of great significance for color patterning in tilapia. Our results suggested that tilapia, a fish with 4 types of pigment cells and a vertically barred wild-type color pattern, together with various natural and artificially induced color gene mutants, can serve as an excellent model system for study color patterning in vertebrates.

Analysis of yellow mutant rainbow trout transcriptomes at different developmental stages reveals dynamic regulation of skin pigmentation genes

“…QDPR serves as another cofactor that is responsible for the regeneration of H4biopterin from quinoid dihydrobiopterin (qBH2) 23 . Another important gene is CSFIR1 , which plays a critical role in development, proliferation, and dispersal of xanthophores 24 , 25 . CSFIR1 can act cell-autonomously within xanthophores, and its mutation can almost eliminate xanthophores, leading to the absence of any orange colour in guppy ( Poecilia reticulate ) 25 .…”

“…Another potentially important DEG is BCO2 (beta-carotene oxygenase 2). As a pivotal gene responsible for carotenoid metabolism, BCO2 is required for carotenoids to contribute to body color in tilapia ( Oreochromis niloticus ), and the expression level of this gene is important for converting colored carotenoids into colorless carotenoids 24 , 40 . In East African cichlid ( Tropheus duboisi ), higher expression of BCO2 was observed in white areas adjacent to yellow skin, and similar results were reported for Chinook salmon ( Oncorhynchus tshawytscha ) 39 , 40 .…”

Oca2targeting using CRISPR/Cas9 in the Malawi cichlidAstatotilapia calliptera

“…other cichlids [13,[29][30][31][32][33][34][35]. HDR on the other hand uses a DNA template to guide the repair, thus by providing a single-stranded DNA (ssDNA) template, one can either insert a sequence of interest (e.g.…”

oca2targeting using CRISPR/Cas9 in the Malawi cichlidAstatotilapia calliptera

“…NHEJ is an imprecise mechanism that generates small insertions or deletions that result in a frameshift. This method has been widely used to induce frameshift mutations in coding protein sequences leading to loss of function alleles in many model systems including other cichlids (Fang et al, 2018;Höch et al, 2021;Kratochwil et al, 2018;Li et al, 2021Li et al, , 2014Livraghi et al, 2021;Rasys et al, 2019;Wang et al, 2021). HDR on the other hand utilises a DNA template to guide the repair, thus by providing a single-stranded DNA (ssDNA) template, one can either insert a sequence of interest (e.g.…”