蒙古绵羊和哈萨克绵羊MHC-DRB_3基因外显子2的多态性

Polymorphisms of Exon 2 of MHC-DRB_3 Gene in Mongolian and Kazakh Sheep

采用PCR RFLP方法对蒙古绵羊和哈萨克绵羊MHC DRB3 基因第 2外显子 2 85bp的扩增产物进行多态性分析 ,共检测到 17种基因型 ,由A、B、C、D、E、F和H共 7个复等位基因控制。通过酶切图谱分析表明 ,蒙古绵羊和哈萨克绵羊的MHC DRB3 基因第 2外显子的第 15 4、16 8和 2 2 0位的碱基表现出多态性。统计分析表明 ,MHC DRB3 基因的部分基因型频率和等位基因频率在两个群体之间差异显著或极显著 (P <0 10、P <0 0 5或P <0 0 1)。χ2 适合性检验结果表明 ,蒙古绵羊和哈萨克绵羊的MHC DRB3 基因第 2外显子的HaeⅢ酶切位点均未达到Hardy Weinberg平衡状态 (P <0 0 1)。

MHC(major histocompatibility complex) is a chromosomal region consisting of a group of closely linked loci which are highly polymorphic,which plays a central role in the immune system of animals and is almost found in all vertebrates.Its expressional product is MHC antigen of which main function is antigen presentation.In this study,the exon 2 of MHC-DRB_3 gene was amplified by PCR and a uniform fragment of 285 bp was obtained in Mongolian Sheep and Kazakh Sheep.The 285 bp PCR product was digested with restriction endomuclease Hae Ⅲ and genetic polymorphism was investigated by PCR-RFLP.Seven alleles were found: A (168 bp/117 bp), B (154 bp/117 bp/14 bp), C (154 bp/65 bp/52 bp/14 bp), D (168 bp/65 bp/52 bp), E (154 bp/131 bp), F (154 bp/66 bp/65 bp), H (220 bp/65 bp).There are seventeen genotypes in the tested populations, BB (154 bp/117 bp/14 bp), CC (154 bp/65 bp/52 bp/14 bp), EE (154 bp/131 bp), HH (220 bp/65 bp), FF (154 bp/66 bp/65 bp), AB (168 bp/154 bp/117 bp/14 bp), AC (168 bp/154 bp/117 bp/65 bp/52 bp/14 bp), AE (168 bp/154 bp/131 bp/117 bp), AH (220 bp/168 bp/117 bp/65 bp), BC (154 bp/117 bp/65 bp/52 bp/14 bp), CE (154 bp/131 bp/65 bp/52 bp/14 bp), CD (168 bp/154 bp/65 bp/52 bp/14 bp), CF (154 bp/66 bp/65 bp/52 bp/1 4bp), CH (220 bp/154 bp/65 bp/52 bp/14 bp), DE (168 bp/154 bp/131 bp/65 bp/52 bp), EH (220 bp/154 bp/131 bp/65 bp), FH (220 bp/154 bp/66 bp/65 bp).By analyzing restriction map,polymorphic sites were detected at base position 154,168 and 220.Statistical results indicated that there are significant differences of some genotypic frequencies and allelic frequencies between Mongolian Sheep and Kazakh Sheep( P<0.10,P <0.05 or P<0.01).CC,FF,BC and B,C,F are favorable genotypes and favorable alleles respectively in Mongolian Sheep and Kazakh Sheep,In addition, Hae Ⅲ CE and Hae Ⅲ E is favorable genotype and favorable allele respectively in Kazakh Sheep.The results of χ 2 test showed that genotypes of MHC-DRB_3 gene in Mongolian Sheep and Kazakh Sheep did not fit with Hardy-Weinberg equilibrium( P <0.01).