Sex Differences in the Brain Transcriptome and the GnRH/GnRHR Gene Family of Siniperca scherzeri

Siniperca scherzeri exhibits significant sexual growth dimorphism, but the mechanism of sex differentiation in its brain remains poorly understood. To reveal the molecular basis of sexual dimorphism, this study performed comparative transcriptome sequencing of male and female brain tissues and systematically identified the GnRH/GnRHR gene family. A total of 1,471 differentially expressed genes were identified, with 804 upregulated in female brains and 667 in male brains. KEGG enrichment revealed significant enrichment of GnRH signaling and Wnt signaling pathways. Furthermore, three GnRH ligands (GnRH1, GnRH2, GnRH3) and two receptors (GnRHR2, GnRHR4) were identified for the first time in S. scherzeri . Phylogenetic analysis and protein structure analysis indicate that these genes are relatively conserved in teleosts. Multi-tissue expression profiling analysis revealed that all GnRH members exhibit significant tissue specificity. Notably, all three GnRH ligands exhibited male-biased expression in the brain, a pattern closely associated with the female-biased growth advantage. These findings suggest that sexually dimorphic GnRH activity serves as a key endocrine mechanism linking the reproductive and growth axes, directing differential energy allocation between sexes and thereby driving sexual dimorphism. This study provides a foundation for understanding the molecular mechanisms underlying sex differentiation and growth regulation in fish.