Studies on the molecular evolution of MHC class I genes and their polymorphism

本研究表明，在T细胞识别的MHC I类分子/肽复合物的基本特征似乎已经建立在脊椎动物进化的早期阶段。我们的研究揭示了MHC I类分子的高度保守性，即肽结合策略的保守性和T细胞受体与MHC I类分子之间界面的保守性。我们还分析了软骨鱼类经典MHC I类基因的基因组结构，发现经典MHC I类基因的外显子/内含子组织基本上在整个有颌脊椎动物的进化过程中高度保守。我们进一步研究了经典的MHC I类和II类基因在软骨鱼之间的联系。结果表明，软骨鱼与硬骨鱼属于同一连锁群，但与哺乳动物、鸟类和两栖类等脊椎动物的连锁群一致。因此，这两类MHC基因之间的联系似乎是原始的，并有很长的进化历史。

The present study suggests that the essential features in the T cell recognition of the MHC class I molecule/peptide complex appear to have been established at the early stage of the vertebrate evolution. Our study revealed highly conserved nature of the MHC class I molecules, namely, conservation of the peptide-binding strategy and conservation of the interface between a T cell receptor and an MHC class I molecule. We also analysed the genomic structure of a cartilaginous fish classical MHC class I gene and found that the exon/intron organization of the classical MHC class I gene is, basically, highly conserved throughout the evolution of the jawed vertebrates. We further examined the linkage between the classical MHC class I and class II genes in the cartilaginous fish. The results indicated that the two MHC classes belong to the same linkage group in the genome of the cartilaginous fish in contrast to the teleost fish but in accordance with the other vertebrate groups such as mammals, birds, and amphibians. Therefore, the linkage between the genes of the two MHC classes appears to be primitive and to have a long evolutionary history.