Gene duplication and fragmentation in the zebra finch major histocompatibility complex.
Gene duplication and fragmentation in the zebra finch major histocompatibility complex.
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DOI：
10.1186/1741-7007-8-29
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发表时间：
2010-04-01
期刊：
影响因子：
5.4
通讯作者：
Edwards SV
中科院分区：
文献类型：
--
作者：
Balakrishnan CN;Ekblom R;Völker M;Westerdahl H;Godinez R;Kotkiewicz H;Burt DW;Graves T;Griffin DK;Warren WC;Edwards SV
主要组织相容性复合体（MHC）由于其高多态性和对疾病抗性的重要性，已成为许多脊椎动物基因组计划的重要焦点。禽类MHC组织特别令人感兴趣，因为鸡的MHC是最具特征的禽类物种，具有高度流线型的最小必需MHC，这与对特定病原体的抵抗力有关。目前尚不清楚这种组织在多大程度上描述了其他鸟类的情况，以及它是否代表了一种衍生的或祖先的状况。斑胸草雀（Taeniopygia guttata）基因组测序，结合靶向细菌人工染色体（BAC）测序，使我们能够表征来自高度分化和多样化的鸟类谱系——雀形目的MHC。斑胸草雀MHC表现出复杂的结构和历史，涉及基因复制和片段化。斑胸草雀的MHC包括多个I类和II类基因，其中一些似乎是假基因，并且比鸡的MHC跨越更广泛的基因组区域，这一点可以从7个BACs上的MHC基因的存在得到证明，这些BACs的长度为739 kb。细胞遗传学（FISH）证据和基因组组装本身将核心MHC基因定位在多达四条染色体上，TAP和I类基因定位在不同的染色体上。MHC II类区域进一步以内源性逆转录病毒含量高为特征。最后，我们发现了强有力的证据，表明选择作用于雀烷类MHC I类和II类基因的位点。斑胸草雀的MHC与鸡的MHC明显不同，鸡是唯一拥有完整基因组序列的鸟类。TAP和表达的MHC I类位点之间明显缺乏同质性，这实际上让人想起了在一些哺乳动物谱系中看到的一种模式，可能代表了趋同进化。我们对斑胸草雀MHC的分析表明，在鸟类MHC的历史中有一个复杂的历史，包括染色体分裂、基因复制和易位，并强调了鸟类谱系中MHC结构和组织的显著差异。
Due to its high polymorphism and importance for disease resistance, the major histocompatibility complex (MHC) has been an important focus of many vertebrate genome projects. Avian MHC organization is of particular interest because the chicken Gallus gallus, the avian species with the best characterized MHC, possesses a highly streamlined minimal essential MHC, which is linked to resistance against specific pathogens. It remains unclear the extent to which this organization describes the situation in other birds and whether it represents a derived or ancestral condition. The sequencing of the zebra finch Taeniopygia guttata genome, in combination with targeted bacterial artificial chromosome (BAC) sequencing, has allowed us to characterize an MHC from a highly divergent and diverse avian lineage, the passerines. The zebra finch MHC exhibits a complex structure and history involving gene duplication and fragmentation. The zebra finch MHC includes multiple Class I and Class II genes, some of which appear to be pseudogenes, and spans a much more extensive genomic region than the chicken MHC, as evidenced by the presence of MHC genes on each of seven BACs spanning 739 kb. Cytogenetic (FISH) evidence and the genome assembly itself place core MHC genes on as many as four chromosomes with TAP and Class I genes mapping to different chromosomes. MHC Class II regions are further characterized by high endogenous retroviral content. Lastly, we find strong evidence of selection acting on sites within passerine MHC Class I and Class II genes. The zebra finch MHC differs markedly from that of the chicken, the only other bird species with a complete genome sequence. The apparent lack of synteny between TAP and the expressed MHC Class I locus is in fact reminiscent of a pattern seen in some mammalian lineages and may represent convergent evolution. Our analyses of the zebra finch MHC suggest a complex history involving chromosomal fission, gene duplication and translocation in the history of the MHC in birds, and highlight striking differences in MHC structure and organization among avian lineages.
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影响因子：
4.9
作者：
Ekblom, Robert;Saether, Stein Are;Hoglund, Jacob
通讯作者：
Hoglund, Jacob
影响因子：
5.4
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