April 21, 2020  |  

The Y chromosome sequence of the channel catfish suggests novel sex determination mechanisms in teleost fish.

Authors: Bao, Lisui and Tian, Changxu and Liu, Shikai and Zhang, Yu and Elaswad, Ahmed and Yuan, Zihao and Khalil, Karim and Sun, Fanyue and Yang, Yujia and Zhou, Tao and Li, Ning and Tan, Suxu and Zeng, Qifan and Liu, Yang and Li, Yueru and Li, Yun and Gao, Dongya and Dunham, Rex and Davis, Kenneth and Waldbieser, Geoffrey and Liu, Zhanjiang

Sex determination mechanisms in teleost fish broadly differ from mammals and birds, with sex chromosomes that are far less differentiated and recombination often occurring along the length of the X and Y chromosomes, posing major challenges for the identification of specific sex determination genes. Here, we take an innovative approach of comparative genome analysis of the genomic sequences of the X chromosome and newly sequenced Y chromosome in the channel catfish.Using a YY channel catfish as the sequencing template, we generated, assembled, and annotated the Y genome sequence of channel catfish. The genome sequence assembly had a contig N50 size of 2.7 Mb and a scaffold N50 size of 26.7 Mb. Genetic linkage and GWAS analyses placed the sex determination locus within a genetic distance less than 0.5?cM and physical distance of 8.9?Mb. However, comparison of the channel catfish X and Y chromosome sequences showed no sex-specific genes. Instead, comparative RNA-Seq analysis between females and males revealed exclusive sex-specific expression of an isoform of the breast cancer anti-resistance 1 (BCAR1) gene in the male during early sex differentiation. Experimental knockout of BCAR1 gene converted genetic males (XY) to phenotypic females, suggesting BCAR1 as a putative sex determination gene.We present the first Y chromosome sequence among teleost fish, and one of the few whole Y chromosome sequences among vertebrate species. Comparative analyses suggest that sex-specific isoform expression through alternative splicing may underlie sex determination processes in the channel catfish, and we identify BCAR1 as a potential sex determination gene.

Journal: BMC biology
DOI: 10.1186/s12915-019-0627-7
Year: 2019

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