Towards the Identification of Sex-Determining Genes in Channel Catfish

Sex is one of the most fundamental features in the life of an organism. In teleost, sex determination mechanism exhibits extraordinary plasticity and diversity with respect to the evolutionary pattern. Catfish possess a male heterogametic sex determination system (XY system). Recent work in our lab identified one Y-linked specific microsatellite marker in channel catfish, which allow rapid identification of sex of channel catfish. To further search for the sex-determining genes in channel catfish, six projects have been carried out to pinpoint the sex-determining region. RNA-Seq of pooled testes from 25 males stemmed from different developmental stages revealed about 300 candidate testis-specific transcripts. To identify the genes expressed exclusively in males during gonad sex differentiation period, another RNA-Seq is being conducted to sequence females and males in sequential early developmental stages. BAC contigs on the putative Y chromosome with the sex-linked marker were sequenced by NGS and the assembly of these contigs is underway. Along with XY male whole genome sequencing and YY male whole genome sequencing, assembly, and then mapping and subtracting the female sequences from the YY or XY sequences, a group of potential candidate male-specific genes can be identified. SNP fine mapping of sex would reveal sex determination loci in catfish and further pin down the number of candidate sex-determining genes in catfish.