[Single nuclear polymorphisms in exon 3 of POMC gene and the association with growth traits in Hu sheep and East Friesian x Hu crossbred sheep].

Pro-opiomelancortin (POMC) plays important roles in the regulation of food intake and energy expenditure. The sheep exon 3 of gene POMC was amplified and sequenced by screening the DNA pools to select single nuclear polymorphisms and analyze the association with the growth traits. Two silent SNP mutations (g.273 T/C and g.456 G/A) in Hu sheep were identified. PCR-restriction fragment length polymorphism (RFLP) was used to test the g.273 T/C and the association between the g.273 T/C polymorphism and some growth traits was analyzed in Hu sheep (n = 162) and East Friesian x Hu crossbred sheep (n=130). The results showed that three genotypes, TT, TC and CC, were detected in Hu sheep with the frequencies of 0.469, 0.438 and 0.093, respectively. Two genotypes, TT and TC, were detected in East Friesian x Hu crossbred sheep with the frequencies of 0.754 and 0.246, respectively. The association analysis showed that in Hu sheep the two-month weaning weight, four-month rump height of genotype CC and the four-month body length, cannon circumference of genotype TC were significantly higher than those of genotype TT (P < 0.05); the four- and six-month weight of genotype CC were significantly higher than those of genotypes TT and TC (P < 0.01); the four-month body height and body length of genotype CC were significantly higher than those of genotypes TT (P < 0.01) and TC (P < 0.05); the four-month cannon circumference of CC genotype was significantly higher than that of TT genotype (P < 0.01). In East Friesian x Hu crossbred sheep the two-month weaning weight, four-month weight, body height, body length, chest depth and cannon circumference of genotype TC were significantly higher than those of genotype TT (P < 0.05); the six-month weight of genotype TC was significantly higher than that of genotype CC (P < 0.01). In conclusion, the exon 3 of gene POMC was associated with growth traits, and C allele was beneficial to the increase of body weight and body size traits of sheep, which potentially afford a good foundation for further study on POMC gene as aided breeding markers for growth traits in sheep.