Molecular Evolution of Major Histocompatibility Complex and T Cell Receptor Genes

该项目的具体目标是i)通过克隆低等脊椎动物的MHC基因来阐明主要组织相容性复合体（MHC）的系统发育起源，ii)确定支配MHC长期进化的一般规则。对于第一个具体目标，我们证明了软骨鱼具有典型的多态MHC基因。然而，所有从环口动物中分离MHC基因的尝试都是不成功的，这表明这些动物可能没有真正的MHC基因。至于第二个具体目标，我们确定了以下三条适用于MHC基因的规则。首先，尽管序列保守性较差，但MHC基因的整体结构域组织在进化中保守性很好。其次，功能重要的多态MHC基因的数量在物种间几乎没有变化，每个单倍型在1到3个之间。第三，MHC多态性的基本特征在进化过程中具有较好的保守性。

The specific aims of this project were i) to clarify the phylogenetic origin of the major histocompatibility complex (MHC) by cloning MHC genes of lower vertebrates, and ii) to identify general rules that govern the long-term evolution of the MHC.As to the first specific aim, we demonstrated that the cartilaginous fish has typical, polymorphic MHC genes.However, all attempts to isolate MHC genes from cyclostomes were unsuccessful, suggestimg that these animals might not have bona fide MHC genes.As to the second specific aim, we identified the following three rules that apply to MHC genes in general.First, overall domain organization of MHC genes is very well conserved in evolution despite the fact that the sequence conservation is poor.Second, the number of functionally important, polymorphic MHC genes shows little interspecies variation and falls between one and three per haplotype.Third, essential features of MHC polymorphism are well conserved in evolution.