Slade R W, Mayer W E
Max-Planck-Institut für Biologie, Abteilung Immungenetik, Tübingen, Germany.
Mol Biol Evol. 1995 May;12(3):441-50. doi: 10.1093/oxfordjournals.molbev.a040219.
The major histocompatibility complex (Mhc) is a multigene family found in vertebrates. Mhc genes code for heterodimeric cell-surface molecules involved in presentation of peptides to T-lymphocytes. There are two classes of Mhc, and in eutherian mammals four main families of class II genes have been recognized; DR, DQ, DP, and DN/DO. Each class II family contains genes that code for one or more alpha and beta chains. Do the class II genes of marsupial mammals belong to any of these eutherian mammal class II families? The results to date are conflicting. The expressed class II beta-chain genes could not be satisfactorily assigned to any eutherian class II gene family and were designated as new gene families, while, conversely, a partial sequence of an expressed alpha-chain gene was clearly very similar to the DNA gene of eutherian mammals. The aim of this study was to conduct a more thorough analysis of the alpha-chain genes in a marsupial by obtaining full-length sequences of all the expressed alpha-chain genes in the red-necked wallaby, Macropus rufogriseus. Two class II alpha-chain genes were isolated from a spleen-derived cDNA library, and both have the potential to code for fully functional MHC molecules. Phylogenetic analysis indicated they belonged to previously identified eutherian class II families and are designated as Maru-DRA and Maru-DNA. Northern blot data indicated processed transcript sizes of approximately 1.6 kb for Maru-DRA and approximately 2.5 kb for Maru-DNA and that the latter was expressed at a lower level than the former. The phylogeny shows that the DR, DQ, DP, and DN/DO gene families diverged prior to the divergence of the marsupial and eutherian mammal lineages.
主要组织相容性复合体（Mhc）是在脊椎动物中发现的一个多基因家族。Mhc基因编码参与将肽呈递给T淋巴细胞的异二聚体细胞表面分子。Mhc有两类，在真兽类哺乳动物中已识别出四个主要的II类基因家族；DR、DQ、DP和DN/DO。每个II类家族都包含编码一条或多条α链和β链的基因。有袋类哺乳动物的II类基因属于这些真兽类哺乳动物II类家族中的任何一个吗？迄今为止的结果相互矛盾。已表达的II类β链基因不能令人满意地归入任何真兽类II类基因家族，因此被指定为新的基因家族，而相反，一个已表达的α链基因的部分序列显然与真兽类哺乳动物的DNA基因非常相似。本研究的目的是通过获得红颈袋鼠（Macropus rufogriseus）所有已表达的α链基因的全长序列，对有袋类动物的α链基因进行更全面的分析。从脾脏来源的cDNA文库中分离出两个II类α链基因，它们都有可能编码具有完全功能的MHC分子。系统发育分析表明它们属于先前鉴定的真兽类II类家族，分别被命名为Maru-DRA和Maru-DNA。Northern印迹数据表明，Maru-DRA的加工转录本大小约为1.6 kb，Maru-DNA的约为2.5 kb，且后者的表达水平低于前者。系统发育显示，DR、DQ、DP和DN/DO基因家族在有袋类和真兽类哺乳动物谱系分化之前就已经分化。
