Evolutionary redefinition of immunoglobulin light chain isotypes in tetrapods using molecular markers
Evolutionary redefinition of immunoglobulin light chain isotypes in tetrapods using molecular markers
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DOI：
10.1073/pnas.0808800105
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发表时间：
2008-10-28
影响因子：
11.1
通讯作者：
Nei, Masatoshi
中科院分区：
文献类型：
--
作者：
Das, Sabyasachi;Nikolaidis, Nikolas;Nei, Masatoshi
免疫球蛋白轻链(IGL)基因的系统发育关系很难解决，因为这些基因很短，进化相对较快。在这里，我们使用保守的氨基酸残基、重组信号序列和IGL基因的基因组结构作为分支标记，将12种四足动物的IGL序列分为三个不同的组(kappa、lambda和sigma异型)。根据标记的分布，我们得出结论，现存最早的四足动物，即两栖动物，具有三种IGL亚型：kappa，lambda和sigma。其中，在爬行动物和一些哺乳动物中也发现了两种(kappa和lambda)。到目前为止，在所有测试的四足动物中都发现了lambda同种类型，而kappa同种类型似乎至少在一些鸟类和微型蝙蝠中丢失了。分支分子标记的保守性表明，它们与三种IGL亚型的功能特化有关。IGL基因座的基因组图谱揭示了在四足动物物种进化过程中发生的多种基因重排。这些重排导致了IGL基因座的基因组长度和IGL组成基因的数目和顺序的种间差异，但IGL基因座的总体组织结构并没有改变。
The phylogenetic relationships of Ig light chain (IGL) genes are difficult to resolve, because these genes are short and evolve relatively fast. Here, we classify the IGL sequences from 12 tetrapod species into three distinct groups (kappa, lambda, and sigma isotypes) using conserved amino acid residues, recombination signal sequences, and genomic organization of IGL genes as cladistic markers. From the distribution of the markers we conclude that the earliest extant tetrapods, the amphibians, possess three IGL isotypes: kappa, lambda, and sigma. Of these, two (kappa and lambda) are also found in reptiles and some mammals. The lambda isotype is found in all tetrapods tested to date, whereas the kappa isotype seems to have been lost at least in some birds and in the microbat. Conservation of the cladistic molecular markers suggests that they are associated with functional specialization of the three IGL isotypes. The genomic maps of IGL loci reveal multiple gene rearrangements that occurred in the evolution of tetrapod species. These rearrangements have resulted in interspecific variation of the genomic lengths of the IGL loci and the number and order of IGL constituent genes, but the overall organization of the IGL loci has not changed.