Cloning and expression of IGF-I, IGF-II, and GHR genes and the role of their single-nucleotide polymorphisms in the growth of pikeperch (Sander lucioperca)

Pikeperch (Sander lucioperca L.) is a freshwater fish species of major economic importance in several producer countries. Insufficient information about growth-related genes in pikeperch prevents their breeding through marker-assisted selection (MAS). This study aimed to clone growth-related genes (IGF-I, IGF-II, and GHR) of pikeperch to detect single-nucleotide polymorphisms (SNPs) associated with growth, laying the foundation for MAS in pikeperch. Full-length cDNA sequences of IGF-I, IGF-II, and GHR were isolated using RACE PCR; the cDNA sequences obtained were 883, 1210, and 1995 base pairs, respectively, encoding proteins of 183, 215, and 664 amino acids. The three genes were expressed in all tissues tested, though at especially high levels in the liver. Four SNPs, comprising two in intron 1 of IGF-I, one in intron 3 of IGF-II, and one in the coding region of GHR, were found in a cultured population of pikeperch. Three of the SNPs were successfully genotyped by Kompetitive allele-specific PCR in a randomly mixed group of 298 individuals. The SNP in IGF-II was significantly associated with body weight (SL2-IGF-II-c.544+1111_544+1112delAAinsTC; allele frequency, AA:TC = 52.8:47.2; AA-AA (26), AA-TC (54), and TC-TC (20) genotypes). The fish with genotype TC-TC of SL2-IGF-II-c.544+1111_544+1112delAAinsTC had a significantly greater body weight than fish of genotype AA-AA (P < 0.05). This discovery may provide a useful marker for marker-assisted selection of pikeperch in the future.