MOLECULAR CHARACTERIZATION AND EXPRESSION ANALYSES OF IGFBP1 (INSULIN-LIKE GROWTH FACTOR BINDING PROTEIN 1) GENE IN BIGHEAD CARP (HYPOPHTHALMICHTHYS NOBILIS)

The gene sequence of insulin-like growth factor binding proteins 1 (IGFBP1) was obtained from the genome of bighead carp (Hypophthalmichthys nobilis), and subsequently, the physicochemical and evolutionary characteristics of the IGFBP1 protein and gene expression were analyzed. The open reading frame (ORF) of bighead carp IGFBP1 is 789 bp, encoding 262 amino acids. The protein has a molecular weight of 28139.23 u and an isoelectric point (pI) of 7.42. Notably, it possesses a signal peptide but lacks a transmembrane structure, suggesting its classification as a hydrophilic secreted protein. Additionally, the IGFBP1 protein in bighead carp contains two conserved IB and TY domains, demonstrating high sequence homology with IGFBP1 in cypriniformes. Spatial and temporal expression analyses of the IGFBP1 gene in bighead carp revealed significantly up-regulation during the segmental stage, contrasting with lower expression levels during the hatching period. In adult fish, the highest expression level was observed in liver, followed by skin, intestine, and gonad, while expression in other tissues remained relatively low. Differential growth analysis showed significant differences in IGFBP1 in liver tissues between large (heavy group) and small (light group) fish (P<0.01), suggesting a positive regulatory role for the IGFBP1 gene in facilitating the rapid growth of bighead carp. The results of this study hold both theoretical significance and potential applications in further elucidating the molecular mechanisms underlying growth regulation and in implementing genetic improvements for farmed bighead carp.