Association analysis of nucleotide polymorphisms in growth hormone (GH) and its receptor (GHR) with body weight in Californian rabbits

Abstract

[EN] The objective of the present study was to evaluate the influence of the genotypes of two single nucleotide polymorphisms (SNPs) c.78C>T located in the growth hormone gene (GH) and c.106C>G in the growth hormone receptor gene (GHR) on individual body weight (IBW) during the growing period at 35, 70 and 90 d of age on a total of 107 weaned Californian breed rabbits. The restriction fragments obtained revealed that 74.8% of the rabbits carrying c.78C>T SNP and 52.3% of the rabbits carrying c.106C>G SNP were heterozygous, which indicated a moderate level of genetic diversity in this Californian population. Association analysis based on a single-gene approach revealed that c.78C>T polymorphism in the GH gene had a significant effect (P<0.05) on the weight at 70 and 90 d of age. The highest IBW (2530.4±66.6 g) was observed in rabbits carrying the c.78C>T TT genotype, and detected individuals were significantly affected by the dominance effect. Significant differences were observed between individuals with homozygous c.106C>G CC genotype and those with heterozygous CG genotype. The highest IBW (2462.0±198.3 g) was observed in rabbits carrying the c.106C>G CC genotype and detected individuals were significantly affected by the additive effect. A total of nine combined genotypes of c.78C>T and c.106C>G SNPs was found in the study, of which only four major groups (CT/CC, CC/CG, CT/CG, and CT/GG) were concerned in the diplotype analysis. Significant differences were observed between individuals with CT/CC and CC/CG genotype combinations, and between those with the CC/CG and CT/GG diplotypes. However, the highest IBW at 90 d of age (2447.2±213.8 g) was observed in rabbits carrying the CT/CC genotype combinations. The highest coefficient of determination found for individual body weight at 90 d of age (R2=10.8%) indicated a high effect of genotype combinations. In conclusion, the results obtained suggested that c.78C>T of GH gene and c.106C>G of GHR gene could be useful candidate genes to improve growth performance in Californian rabbits with potential application in rabbit breeding programmes.