Two ancient allelic lineages at the single classical class I locus in the Xenopus MHC.
Two ancient allelic lineages at the single classical class I locus in the Xenopus MHC.
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DOI：
10.4049/jimmunol.163.7.3826
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发表时间：
1999-10
影响因子：
4.4
通讯作者：
M. Flajnik;Y. Ohta;A. Greenberg;L. Salter-Cid;A. Carrizosa;L. Du Pasquier;M. Kasahara
中科院分区：
文献类型：
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作者：
M. Flajnik;Y. Ohta;A. Greenberg;L. Salter-Cid;A. Carrizosa;L. Du Pasquier;M. Kasahara
与迄今为止检查的所有其他脊椎动物不同，非洲爪蟾MHC中只有一个可检测的I类基因座。由于该基因几乎普遍存在且在组织中高表达，广泛的多态性和MHC连锁，该基因属于经典或Ia类基因。由八种确定的MHC单倍型编码的Ia类cDNA的测序分析揭示了两种非常古老的等位基因谱系，它们可能是在1亿年前人类和小鼠从一个共同祖先分化出来时出现的。这些谱系的空前年龄表明，来自实验室模型非洲爪蟾祖先的不同Ia类基因现在在这个物种中表达为等位基因。谱系最好由其细胞质和α 2肽结合结构域定义，并且在每个谱系中存在高度多样的等位基因（由α 1肽结合结构域定义）。令人惊讶的是，α 3结构域在两个谱系中均质化，表明等位基因间的基因转换/重组保持了高序列相似性。
Unlike all other vertebrates examined to date, there is only one detectable class I locus in the Xenopus MHC. On the bases of a nearly ubiquitous and high tissue expression, extensive polymorphism, and MHC linkage, this gene is of the classical or class Ia type. Sequencing analysis of class Ia cDNAs encoded by eight defined MHC haplotypes reveals two very old allelic lineages that perhaps emerged when humans and mice diverged from a common ancestor up to 100 million years ago. The unprecedented age of these lineages suggests that different class Ia genes from ancestors of the laboratory model Xenopus laevis are now expressed as alleles in this species. The lineages are best defined by their cytoplasmic and alpha2 peptide-binding domains, and there are highly diverse alleles (defined by the alpha1 peptide-binding domain) in each lineage. Surprisingly, the alpha3 domains are homogenized in both lineages, suggesting that interallelic gene conversion/recombination maintains the high sequence similarity.