Mayer W E, Williams N S, O'hUigin C, Vincek V, Zaleska-Rutczynska Z, Klein J
Max-Planck-Institut für Biologie, Abteilung Immungenetik, Tübingen, Germany.
Mol Phylogenet Evol. 1993 Mar;2(1):23-30. doi: 10.1006/mpev.1993.1004.
Marsupials are one of three main evolutionary lineages in mammals, the other two being the monotremes and the placental mammals. The marsupial and the placental lineages separated between 120 and 156 million years ago. In this communication, we provide the first molecular description of class I major histocompatibility complex (Mhc) genes in a representative of the marsupial lineage, the red-necked wallaby, Macropus rufogriseus. Three different, nearly full-length class I Mhc sequences were identified in the cDNA library prepared from spleen mRNA of a single wallaby. The three sequences identify at least two loci. Under the assumption that two of the identified sequences are alleles, we designate the three wallaby genes Maru-Mhc-UA01, Maru-Mhc-UA02, and Maru-Mhc-UB*01. The three Maru sequences share several codon deletions and insertions not found in the class I genes of placental mammals. Comparisons of genetic distances among the known class I genes suggest that the Maru genes arose from one ancestral element, whereas the class I genes of the placental mammals arose from another, different ancestral element. The absence of an identifiable defect in the three Maru sequences suggests that the genes from which they were derived are functional. Hence, as in placental mammals, there appear to be two functional class I Mhc loci in the marsupials as well.
有袋类动物是哺乳动物三大主要进化谱系之一，另外两类是单孔目动物和胎盘哺乳动物。有袋类动物和胎盘哺乳动物的谱系在1.2亿至1.56亿年前分化。在本论文中，我们首次对有袋类动物谱系的代表——赤褐袋鼠（Macropus rufogriseus）的I类主要组织相容性复合体（Mhc）基因进行了分子描述。从一只袋鼠脾脏mRNA制备的cDNA文库中鉴定出三个不同的、近乎全长的I类Mhc序列。这三个序列至少确定了两个基因座。假设鉴定出的两个序列是等位基因，我们将这三个袋鼠基因命名为Maru-Mhc-UA01、Maru-Mhc-UA02和Maru-Mhc-UB*01。这三个Maru序列有几个密码子缺失和插入，在胎盘哺乳动物的I类基因中未发现。已知I类基因之间的遗传距离比较表明，Maru基因起源于一个祖先元件，而胎盘哺乳动物的I类基因起源于另一个不同的祖先元件。这三个Maru序列中没有可识别的缺陷，表明它们所源自的基因是有功能的。因此，与胎盘哺乳动物一样，有袋类动物中似乎也有两个功能性的I类Mhc基因座。
