PLAG1 g.8795C>T Mutation Regulates Early Body Weight in Hu Sheep by Weakening miR-139 Binding.

Sheep birth and weaning weights indicate their growth and survival. Thus, identifying molecular genetic markers for early body weight is important in sheep breeding. Pleomorphic adenoma gene 1 (PLAG1) is important for regulating birth weight and body length in mammals; however, its relationship with sheep body weight remains unknown. Here, the 3'-untranslated region (3'-UTR) of the Hu sheep PLAG1 gene was cloned, single nucleotide polymorphisms (SNPs) were screened, genotype-early body weight relationships were analyzed, and the possible molecular mechanism was explored. PLAG1 3'-UTR sequences with five forms of base sequences plus poly(A) tails were detected in Hu sheep and the g.8795C>T mutation was identified. Luciferase reporter assay indicated that the g.8795C>T mutation influenced PLAG1 post-transcriptional activity. miRBase prediction showed that the g.8795C>T mutation was located in the miR-139 seed sequence binding region, and miR-139 overexpression significantly decreased both PLAG1-CC and PLAG1-TT activities. Moreover, the luciferase activity of PLAG1-CC was significantly lower than that of the PLAG1-TT, but miR-139 inhibition substantially increased both PLAG1-CC and PLAG1-TT luciferase activities, suggesting that PLAG1 is the target gene of miR-139. Thus, the g.8795C>T mutation upregulates PLAG1 expression by weakening its binding with miR-139, promoting PLAG1 expression, and increasing Hu sheep birth and weaning weights.

[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.