Generation and maintenance of diversity in the cattle MHC class I region
Generation and maintenance of diversity in the cattle MHC class I region
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DOI：
10.1007/s00251-006-0137-y
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发表时间：
2006-08-01
期刊：
影响因子：
3.2
通讯作者：
Ellis, Shirley A.
中科院分区：
文献类型：
--
作者：
Birch, James;Murphy, Lisa;Ellis, Shirley A.
主要组织相容性复合体（MHC）I类基因在针对细胞内病原体的免疫防御中起着至关重要的作用。一个重要的进化策略是在这些基因中产生和维持高水平的多样性。人类表达三种高度多态性的经典MHC I类基因（HLA-A、HLA-B和HLA-C）。相反，一些物种，例如大鼠和恒河猴，通过产生在转录基因的数量和组合方面差异很大的单倍型来保持多样性。牛似乎使用这两种策略。我们发现，六个明显的经典基因，其中三个是高度多态性的各种组合，在不同的单倍型转录。尽管在cDNA和gDNA中鉴定了额外的序列，但不可能将它们分配给任何这些定义的基因。大多数是高度分歧或非经典的I类基因。因此，我们发现很少有证据表明，在其他一些物种中报道的经典I类基因的频繁重复和缺失。然而，维持牛的I类多样性可能涉及有限的基因改组和删除，可能是由于I类区域内的不平等交换。
Major histocompatibility complex (MHC) class I genes play a crucial role in the immune defence against intracellular pathogens. An important evolutionary strategy is to generate and maintain a high level of diversity in these genes. Humans express three highly polymorphic classical MHC class I genes (HLA-A, HLA-B and HLA-C). In contrast, some species, for example rat and rhesus macaque, maintain diversity by generation of haplotypes that vary considerably with regard to the number and combination of transcribed genes. Cattle appear to use both strategies. We show that various combinations of six apparently classical genes, three of which are highly polymorphic, are transcribed on different haplotypes. Although additional sequences were identified in both cDNA and gDNA, it was not possible to assign them to any of these defined genes. Most were highly divergent or were non-classical class I genes. Thus, we found little evidence for frequent duplication and deletion of classical class I genes as reported in some other species. However, the maintenance of class I diversity in cattle may involve limited gene shuffling and deletion, possibly as a result of unequal crossing-over within the class I region.