奶牛TLR4基因的多态性与乳房炎的相关性研究

TLR4通过识别病原体而激活免疫细胞,在先天免疫和适应性免疫防御中起着重要作用。以中国荷斯坦奶牛、三河牛和中国西门塔尔牛为研究对象,以TLR4为乳房炎抗性的候选基因,分别扩增316bp和382bp2个片段,分别采用SSCP和RFLP-AluⅠ方法来检测TLR4基因的多态性。结合测序发现:在intron1的第4,525bp处的A→G的突变,和exon3的第1,397bp处的T→C突变,使得产生多态。2个位点的A、B等位基因在3个群体中都有分布,且处于中度多态。χ2适合性检验表明,3个群体在这2个位点的突变达到Hardy-Weinberg平衡状态(P>0.05)。运用SAS8.0软件采用最小二乘法拟合线性模型,将基因座不同基因型与奶牛乳房炎进行了关联分析,结果表明:T4CRBR1的AA基因型为乳房炎抗性基因型(P<0.05),A等位基因为乳房炎抗性的有利基因,T4CRBR2的各基因型个体间的体细胞评分差异不显著(P>0.05)。

Genetic Polymorphism of TLR4 Gene and Correlation with Mastitis in Cattle

Toll-like receptor 4 (TLR4) recognizes pathogen ligands and mediates signaling to initiate innate and adaptive immune responses. In this experiment, a 316 bp and 382 bp fragments of TLR4 gene named T4CRBR1 and T4CRBR2, of Chinese Holstein, Sanhe cattle, and Chinese Simmental was amplified by polymerase chain reaction (PCR), respectively. The genetic polymorphisms in the three populations were detected by Single-Strand Conformational Polymorphism (SSCP) in the first locus and by digesting the fragments with restriction endonuclease Alu? in the second one. Results showed that both alleles (A and B) of two loci were found in all the three populations and the value of polymorphism information content (PIC) indicated that these were a moderate polymorphism. Statistical results of χ² test indicated that two polymorphism sites in the three populations fitted with Hardy–Weinberg equilibrium (P > 0.05). After sequencing, A-G single nucleotide polymorphism (SNP) was identified at nucleotide 4,525 in intron 1 of TLR4 gene and C-T SNP was identified at nucleotide 1,397 in exon 3 of TLR4 gene. Meanwhile, the effect of polymorphism of TLR4 gene on somatic cell score (SCS) was analyzed, the results indicated that the cattle with allele A in T4CRBR1 showed lower somatic cell score than that of allele B (P < 0.05). In short, the allele A might play an important role in mastitis resistance in bovine.