Association Of Transforming Growth Factor-β1 Gene Polymorphisms With Litter Size In Pigs

As a multifunctional cytokine, the transforming growth factor β1 (TGF-Bl) functions in epithelial cell proliferation, wound healing, immune response, angiogenesis and embryogenesis. In this experiment, We selected TGF-Bl as the candidate gene affecting litter size in pigs. We detected the polymorphisms of this gene by PCR-SSCP (single-strand conformation polymorphism ) in Large white (567), Landrace (174), Pietrain (39), Synthetic (56) and Erhualian(34), genetic correlation between the polymorphisms of TGF-Bl gene and litter size was analyzed.PCR-SSCP analysis was employed on a majority of TGF-β1 gene cDNA sequence, the intron 4 and the intron 6. The result showed that C→T mutation at 32nt (GenBank NO: AF461809) found in the intron 4 and G→A mutation at 179nt, C→T mutation at 1043nt (GenBank NO: AJ621785) found in the intron6, GG→AA linkage mutations at 2490nt and 2494nt respectively (GenBank NO: M23703) found in the 3' flanking region. The haplotype analysis of five SNPs indicated that there are mainly two haplotypes of CGCAA(sign: A )and TATGG(sign: K ) in the experiment groups. Haplotype A is dominance in import breeds such as Large white, Landrace, Pietrain, and Synthetic, while haplotype K is dominance in Chinese native pig breed of Erhualian.Linear model was conducted for estimating the haplotypic combinations (HC) effects of KK, AK and AA. Least squares means for tatal number born (TNB) and number born alive (NBA) of the first and the second parities of KK were higher than that of AK and AA. By T test, the least squares mean for TNB of the first parity in KK was 1.02 piglets/litter higher than that of AK (P<0. 05), 0.49 piglets/litter higher than that of AA (P>0. 1). while the least squares mean for TNB of the first parity in AA was 0.53 piglets/litter higher than that of AK (P<0. 1). The result indicated that the KK genotype was significantly associated with litter size.Level of TGF-Bl in plasma of pregnant day 10,15, 21,70 and day 3 after weaning was assayed by the quantitative sandwich enzyme immunoassay technique. Individuals of HC AA and HC AK were investigated. For the AA genotype sows, TGF-Bl level at day 3 after weaning was much higher those at pregnancy. During pregnant period , level of TGF-Bl at day 10 was higher and declined gradually . Similarity occurred in AK genotype sows.The data further highlight TGF-β1 gene is associated with increased litter size.