Locus specificity of polymorphic alleles and evolution by a birth-and-death process in mammalian MHC genes
Locus specificity of polymorphic alleles and evolution by a birth-and-death process in mammalian MHC genes
复制标题
DOI：
10.1093/oxfordjournals.molbev.a026097
复制
发表时间：
1999-02-01
影响因子：
10.7
通讯作者：
Nei, M
中科院分区：
文献类型：
--
作者：
Gu, X;Nei, M
我们已经进行了广泛的系统发育分析的多态性等位基因从人类和小鼠的主要组织相容性复合体（MHC）I类和II类基因。从212个完整的人类I类等位基因序列（HLA-A、-B和-C）获得的系统发育树显示，除了一个HLA-B等位基因（HLA-B*7301）之外，来自同一基因座的所有等位基因形成一个单一的簇，该簇得到bootstrap值的高度支持。小鼠MHC I类基因座没有表现出位点特异性的多态性等位基因簇。这被认为是因为基因座间的遗传交换或目前不同单倍型中基因座的混淆指定。在人类和小鼠MHC II类基因座中也观察到多态性等位基因的基因座特异性。因此得出结论，基因座间重组或基因转换是不是非常重要的MHC多样性，与小鼠I类基因座的可能例外。根据完整编码序列的系统发育树，我们将人类MHC I类（HLA-A、-B和-C）和II类（DRB 1）等位基因分为3 ~ 5个主要等位基因谱系（群），这些谱系具有较高的自举值，具有单系性。即使在基于单个外显子的系统发育树中，这些等位基因组中的大多数也保持不变，尽管这并不排除涉及短DNA片段的基因座内重组的可能性。这些结果与以前的观察，MHC基因座是经常重复和删除，以及平衡选择，表明在哺乳动物中的MHC进化是与出生和死亡的进化模型，而不是协同进化的模型。
We have conducted an extensive phylogenetic analysis of polymorphic alleles from human and mouse major histocompatibility complex (MHC) class I and class II genes. The phylogenetic tree obtained for 212 complete human class I allele sequences (HLA-A, -B, and -C) has shown that all alleles from the same locus form a single cluster which is highly supported by bootstrap values, except for one HLA-B allele (HLA-B*7301). Mouse MHC class I loci did not show locus-specific clusters of polymorphic alleles. This was considered to be because of either interlocus genetic exchange or the confusing designation of loci in different haplotypes at the present time. The locus specificity of polymorphic alleles was also observed in human and mouse MHC class II loci. It was therefore concluded that interlocus recombination or gene conversion is not very important for generating MHC diversity, with a possible exception of mouse class I loci. According to the phylogenetic trees of complete coding sequences, we classified human MHC class I (HLA-A, -B, and -C) and class II (DRB1) alleles into three to five major allelic lineages (groups), which were monophyletic with high bootstrap values. Most of these allelic groups remained unchanged even in phylogenetic trees based on individual exons, though this does not exclude the possibility of intralocus recombination involving short DNA segments. These results together with the previous observation that MHC loci are subject to frequent duplication and deletion, as well as to balancing selection, indicate that MHC evolution in mammals is in agreement with the birth-and-death model of evolution, rather than with the model of concerted evolution.