民猪的SLA-DRB基因的PCR-RFLP多态性分析

采用克隆测序和PCR-RFLP相结合的方法,对民猪的SLA-DRB基因的整个编码区进行了扫描和多态性分析.结果表明该基因的第2外显子是整个基因的高变区,突变率达到5.6%,其中80%为有效突变,但没有发现新的等位基因;PCR-RFLP结果表明外显子1用内切酶Alu Ⅰ酶切可获得3种基因型;外显子2用内切酶Taq Ⅰ酶切可获得3种基因型;外显子3用内切酶Bcn Ⅰ酶切可获得3种基因型;外显子4用内切酶Mbo Ⅰ酶切可获得2种基因型;外显子5用内切酶Hin1 Ⅰ酶切可获得3种基因型.Hardy-Weinberg平衡分析表明民猪在Alu Ⅰ和Hin1 Ⅰ处于平衡状态(P＞0.05),在Taq Ⅰ、Bcn Ⅰ和Mbo Ⅰ处于不平衡状态.     

民猪的SM-DRB基因的PCR-RFLP多态性分析

采用克隆测序和PCR—RFLP相结合的方法,对民猪的SLA—DRB基因的整个编码区进行了扫描和多态性分析．结果表明该基因的第2外显子是整个基因的高变区,突变率达到5．6％,其中80％为有效突变,但没有发现新的等位基因;PCR-RFLP结果表明外显子1用内切酶Alu Ⅰ酶切可获得3种基因型;外显子2用内切酶TaqⅠ酶切可获得3种基因型：外显子3用内切酶BcnⅠ酶切可获得3种基因型：外显子4用内切酶MboⅠ酶切可获得2种基因型：外显子5用内切酶HinlⅠ酶切可获得3种基因型．Hardy-Weinberg平衡分析表明民猪在Alu Ⅰ和HinlⅠ处于平衡状态（P〉0．05）．在TaqⅠ、BcnⅠ和MboⅠ处于不平衡状态．     

Allelic diversity at class II DRB1 and DQB loci of the pig MHC (SLA)

 The loci encoding the β chain of the pig major histocompatibility complex (MHC) class II antigens, SLA-DR and -DQ, have been known to exhibit a remarkable degree of allelic polymorphism. Here, to understand the generation of SLA class II polymorphism, 25 SLA-DRB1 and 24 SLA-DQB genes including newly identified 12 SLA-DRB1 and 7 SLA-DQB genes obtained from miniature pigs were analyzed based on the nucleotide and deduced amino acid sequences. Most of the allelic diversity was attributed to the variable sequences which encode a β₁ domain consisting of a β-pleated sheet followed by an α helix. In the β₁ domain coding region, there were four GC-rich sequences, which have been considered to involve the intra-exon sequence exchange also in other gene evolutions. The first and second GC-rich sequences were χ-like sequences, which have been shown to be a putative recombination signal, and were stably conserved among SLA-DRB1 and DQB genes. These χ-like sequences identified in SLA-DRB1 and SLA-DQB were found to encode the first turning point of the β-pleated sheet and the boundary between the β-pleated sheet and the α helix. Analysis of clustered sequence variation also suggested intra-exon gene conversions in which the χ-like sequences act as putative breakpoints. In addition to point mutations and selection mechanism, intra-exon gene conversions must be an important mechanism in the generation of allelic polymorphism at the SLA-DRB1 and SLA-DQB. Received: 3 December 1998 / Revised: 29 June 1999