Evolutionary Genetics, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany.
Immunogenetics. 2012 Jul;64(7):535-47. doi: 10.1007/s00251-012-0609-1. Epub 2012 Mar 20.
Genes of the major histocompatibility complex (MHC) play a pivotal role in the vertebrate immune system and are attractive markers for functional, fitness-related, genetic variation. Although bats (Chiroptera) represent the second largest mammalian order and are prone to various emerging infectious diseases, little is known about MHC evolution in bats. In the present study, we examined expressed MHC class II DRB sequences (exons 1 to 4) of New World bat species, Saccopteryx bilineata, Carollia perspicillata, Noctilio albiventris and Noctilio leporinus (only exon 2). We found a wide range of copy number variation of DRB loci with one locus detected in the genus Noctilio and up to ten functional loci observed in S. bilineata. Sequence variation between alleles of the same taxa was high with evidence for positive selection. We found statistical support for recombination or gene conversion events among sequences within the same but not between bat species. Phylogenetic relationships among DRB alleles provided strong evidence for independent evolution of the functional MHC class II DRB genes in the three investigated species, either by recent gene duplication, or homogenization of duplicated loci by frequent gene conversion events. Phylogenetic analysis of all available chiropteran DRB exon 2 sequences confirmed their monophyletic origin within families, but revealed a possible trans-species mode of evolution pattern in congeneric bat species, e.g. within the genera Noctilio and Myotis. This is the first study investigating phylogenetic relationships of MHC genes within bats and therefore contributes to a better understanding of MHC evolution in one of the most dominant mammalian order.
主要组织相容性复合体（MHC）基因在脊椎动物免疫系统中起着关键作用，是功能、适应相关遗传变异的有吸引力的标记。尽管蝙蝠（翼手目）是第二大哺乳动物目，容易发生各种新发传染病，但对蝙蝠 MHC 进化知之甚少。在本研究中，我们研究了新世界蝙蝠物种 Saccopteryx bilineata、Carollia perspicillata、Noctilio albiventris 和 Noctilio leporinus（仅外显子 2）的表达 MHC 类 II DRB 序列（外显子 1 至 4）。我们发现 DRB 基因座的拷贝数变异范围很广，在 Noctilio 属中检测到一个基因座，在 S. bilineata 中观察到多达十个功能基因座。同一分类单元等位基因之间的序列变异很大，有正选择的证据。我们发现，在同一蝙蝠物种内的序列之间存在重组或基因转换事件的统计支持，但在蝙蝠物种之间没有发现。DRB 等位基因之间的系统发育关系为三个研究物种中功能性 MHC 类 II DRB 基因的独立进化提供了强有力的证据，这是通过最近的基因复制或频繁的基因转换事件使重复基因座同质化来实现的。对所有可用的翼手目 DRB 外显子 2 序列的系统发育分析证实了它们在科内的单系起源，但在同种蝙蝠物种中揭示了可能的跨物种进化模式，例如在 Noctilio 和 Myotis 属中。这是第一项研究蝙蝠 MHC 基因系统发育关系的研究，因此有助于更好地了解在最占主导地位的哺乳动物目中之一的 MHC 进化。
