Gene duplications and sequence polymorphism of bovine class II DQB genes
Gene duplications and sequence polymorphism of bovine class II DQB genes
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DOI：
10.1007/bf00185115
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发表时间：
2004
期刊：
影响因子：
3.2
通讯作者：
S. Sigurdardóttir;C. Borsch;K. Gustafsson;L. Andersson
中科院分区：
文献类型：
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作者：
S. Sigurdardóttir;C. Borsch;K. Gustafsson;L. Andersson
通过聚合酶链式反应扩增和DNA测序分析了牛IIDQB类基因的遗传多样性。通过限制性片段长度多态性(RFLP)分析，从代表14个II类单倍型的基因组DNA中扩增出第一个结构域外显子。从某些单倍型中分离到两个DQB序列，证实了DQB基因拷贝数的多态。发现了4种牛DQB基因亚型，DQB1是主要亚型，几乎在所有单倍型中都存在；DQB2与DQB1非常相似，但仅在重复单倍型中发现；DQB3和DQB4是两个完全不同的基因，仅存在于某些重复单倍型中。因此，牛DQB区的复杂性类似于人类DRB区。结果表明，牛DQB基因具有较高的多态性，为tenDQB1等位基因，共鉴定出4个DQB2等位基因。观察到的序列多态与先前定义的DQBRFLP有很好的相关性。牛和人的DQB等位基因在氨基酸水平上表现出惊人的相似性。相比之下，DQB等位基因在物种间的比较中沉默替换的频率比物种内的高得多，排除了自人和牛的分化以来任何一个同时代的DQB等位基因保持的可能性。DQB等位基因之间的沉默替换频率在牛身上明显低于人，这与之前对人和牛DRB等位基因的比较一致。
The genetic diversity of bovine class IIDQBgenes was investigated by polymerase chain reaction amplification and DNA sequencing. The first domain exon was amplified from genomic DNA samples representing 14 class II haplotypes, defined by restriction fragment length polymorphism (RFLP) analysis. The presence of a polymorphism in the copy number ofDQBgenes was confirmed since twoDQBsequences were isolated from certain haplotypes. Four subtypes of bovineDQBgenes were found.DQB1is the major type and was found in almost all haplotypes.DQB2is very similarDQB1but was found only in the duplicated haplotypesDQ9to12.DQB3andDQB4are two quite divergent genes only present in certain duplicated haplotypes. The bovineDQBcomplexity thus resembles that in the humanDRBregion. BovineDQBgenes were found to be highly polymorphic as tenDQB1alleles and fourDQB2alleles were identified. The observed sequence polymorphism correlated well with previously definedDQBRFLPs. Bovine and humanDQBalleles show striking similarities at the amino acid level. In contrast, the frequency of silent substitutions is much higher in comparisons ofDQBalleles between species than within species ruling out the possibility that any of the contemporaryDQBalleles have been maintained since the divergence of humans and cattle. The frequency of silent substitutions betweenDQBalleles was markedly lower in cattle than in humans, in agreement with a previous comparison of human and bovineDRBalleles.