Generation of albino via SLC45a2 gene targeting by CRISPR/Cas9 in the marine medaka Oryzias melastigma.

To produce albinism in the marine medaka Oryzias melastigma, we disrupted the solute carrier family 45 (SLC45a2) gene by clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 with a single guide RNA (sgRNA). Selected sgRNAs were able to target a SLC45a2 gene as confirmed by genotyping and heteroduplex mobility assay (HMA). Of the survived embryos after injection, 54.2% and 60.0% embryos exhibited albinism phenotype by sgRNA1 and sgRNA2, respectively. Deep sequencing at the on-target sites showed different insertion and deletion (indel) mutation profiles near the DNA cleavage sites, indicating high efficacy of producing SLC45a2 knock-out mutants by this method. Moreover, HMA at the potential off-target sites revealed that off-target activity would be induced at a low rate, or not induced at all. This albino marine medaka will be a good model for marine molecular ecotoxicology in establishment of diverse in vivo endpoints, and the application of this efficient gene targeting method in the marine medaka would be useful tool for mechanistic approaches.