Characterization of the sex associated region in the sablefish genome
Date
2026
Authors
Carlow-Ujiie, Tasmin
Journal Title
Journal ISSN
Volume Title
Publisher
University of Victoria
Abstract
The locus that determines sex in sablefish (Anoplopoma fimbria) and a putative master sexdetermining gene, gsdf, were mapped to chromosome 14 in 2013. In 2021, the role of gsdf was confirmed and the allele responsible for sex was characterized to be a 936 transposable element insertion upstream of gsdf that upregulates expression in developing testis and determines maleness via a male heterogametic (XX/XY) system. According to classical theory of sex chromosome evolution, a sex-determining mutation creating a master sex-determining (MSD) gene is followed by recombination suppression spreading from that locus and eventual chromosome degradation and differentiation which ultimately produces heteromorphic sex chromosomes. In sablefish, it was not clear whether X and Y versions of chromosome 14 differed beyond the gsdf insertion. In this study, we used genome wide association studies (GWAS) and linkage disequilibrium (LD) analyses to define boundaries of the sex-associated region (SAR). We found that loci with genotype frequencies that differed between males and females were distributed across a large region of chromosome 14 (38,000 bp). Genes within this block include LOCI129102360, nup54, LOCI129102793, and gsdf. A weaker male-specific block of LD beyond the SAR included aff1. Alleles of nup54, LOCI129102793, and aff1 on the gsdfY-bearing (Y) chromosome differed nonsynonymously from X-linked counterparts. These genes therefore appear to be ‘founder loci’ of an emerging sex-determining region. Moving forward, characterization of the SAR at this stage of sex chromosome evolution will explicate the rate and progression of the sex-determination system in sablefish.
Supervisor: Dr. John S. Taylor