Cloning, SNP detection, and growth correlation analysis of the 5' flanking regions of two myosin heavy chain-7 genes in Mandarin fish (Siniperca chuatsi).

Abstract

Myosin heavy chains (MYHs) play important roles in muscle growth and contraction. In fish, MYHs contribute to hyperplasia and hypertrophy of muscle fibers, which can continue into adult life and thus result in indeterminate growth in some species. We previously identified two MYH genes, MYH-7a and MYH-7b, that are differentially expressed in Mandarin fish (Siniperca chuatsi) and appear to function in early growth. However, the regulatory role of their 5' flanking regions is unknown. To examine the effects of single nucleotide polymorphisms (SNPs) in these regions, we used genome walking to amplify their flanking sequences and analyzed the regulatory elements and binding sites. A single SNP locus was found in the flanking sequence of each gene. These SNP loci are located in the conserved glucocorticoid receptor binding region (MYH-7a: G-614A; Allele frequency: G:A = 94.9:5.1; GG (89.76) and AG (10.24) genotypes) and the LIM homeobox domain transcription factor binding sequence (MYH-7b: C-1933A; Allele frequency: C:A = 54.8:45.2; AA (20.82), AC (48.81), and CC (30.37) genotypes). At the G-614A loci, the GG genotype exhibited more superior growth traits (total length, body length, body height, etc.) than the AG genotype, with the exception of caudal peduncle length. Alternatively, at the C-1933A loci, the AC and AA genotypes showed significant differences in all growth traits, except for head length, with AC exhibiting superior traits. The AA and CC genotypes showed significant differences in caudal peduncle length and height, while no differences were observed between the AC and CC genotypes. Thus, these SNPs in the 5' flanking regions of MYH-7a and MYH-7b are correlated with superior growth and can be used for selecting Mandarin fish during breeding.