Hepatic Transcriptomics Reveals Sexually Dimorphic Expression of IGF/IGFR Genes Underlying Growth Differences in Spinibarbus hollandi.

Sexual dimorphism in growth is a major factor affecting the economic efficiency of fish aquaculture; however, its molecular underpinnings remain incompletely elucidated. We combined comparative liver transcriptomics with genome-wide screening to identify growth-related genes in female and male S. hollandi. We identified 1063 differentially expressed genes (DEGs), with 869 being significantly upregulated in females. KEGG enrichment analysis revealed key growth-related pathways, including Growth hormone synthesis, secretion and action, mTOR, insulin and MAPK signaling pathway were significantly enriched. Furthermore, we identified seven core IGF system components at the genomic level: four ligands (igf1, igf2a, igf2b, igf3) and three receptors (igf1ra, igf1rb, igf2r). Phylogenetic and protein structure analyses indicated high conservation of these genes among teleosts. Multi-tissue expression profiling revealed marked tissue specificity and sexual dimorphism for several IGF members. Notably, hepatic expression levels of igf1, igf2a, igf2b, and igf1ra were significantly higher in females than in males. This expression pattern correlates with the faster female growth phenotype. Here, we present the first systematic characterization of the IGF/IGFR gene family in S. hollandi and based on comparative hepatic transcriptomics targeting growth-related pathways, suggesting that sexually dimorphic activity of the hepatic IGF system may serve as a central regulatory mechanism at the transcriptional level driving growth dimorphism. These findings offer novel theoretical insights and candidate genes for understanding the molecular mechanisms of sexual growth differences in fish and for advancing molecular breeding.