Are ribosomal DNA clusters rearrangement hotspots?: a case study in the genus Mus (Rodentia, Muridae).
Are ribosomal DNA clusters rearrangement hotspots?: a case study in the genus Mus (Rodentia, Muridae).
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DOI：
10.1186/1471-2148-11-124
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发表时间：
2011-05-13
影响因子：
3.4
通讯作者：
Britton-Davidian J
中科院分区：
文献类型：
--
作者：
Cazaux B;Catalan J;Veyrunes F;Douzery EJ;Britton-Davidian J
比较基因组学的最新进展极大地提高了我们对哺乳动物核型结构进化的了解。其中一项突破是进化断点优先定位在富含重复序列（片段重复、端粒和着丝粒）的区域。在这种情况下，我们研究了核糖体基因对基因组重排的贡献，因为它们通常位于着丝粒周围或亚端粒区域，并在不同染色体上形成重复簇。目标模型是小鼠属，它表现出高比率的核型变化，其中很大一部分涉及着丝粒。通过对 19 个物种的小鼠探针进行原位杂交，确定了 rDNA 簇的染色体分布。使用基于分子的参考树，重建了属内簇的系统发育分布，并通过最大似然分析测试了 rDNA 簇、断点和着丝粒之间的时间关联。我们的结果强调了鼠属 rDNA 簇动态的以下特征：i）rDNA 簇在物种之间显示出广泛的数量多样性和几乎唯一的着丝粒周围位置，ii）检索到 rDNA 位点和着丝粒之间的强关联，这可能与它们协同进化的共同约束有关，iii）观察到的断点中有 24% 映射在 rDNA 簇附近，iv）相当大的比例 rDNA 簇变化（插入、删除）也在没有染色体重排的情况下发生。这项关于小鼠属内 rDNA 簇动态的研究揭示了 rDNA 簇和着丝粒之间强烈的进化关系。这两种基因组结构都与小鼠属的断点一致，表明着丝粒区域大量重复的积累可能有助于在该群体中观察到的高水平染色体重新模式。然而，在染色体不变进化枝中观察到的 rDNA 变化率升高表明这些序列的存在不足以导致基因组不稳定。与最近的研究一致，这些结果表明可能需要其他因素（例如 DNA 表观遗传状态的修饰）来触发进化可塑性。
Recent advances in comparative genomics have considerably improved our knowledge of the evolution of mammalian karyotype architecture. One of the breakthroughs was the preferential localization of evolutionary breakpoints in regions enriched in repetitive sequences (segmental duplications, telomeres and centromeres). In this context, we investigated the contribution of ribosomal genes to genome reshuffling since they are generally located in pericentromeric or subtelomeric regions, and form repeat clusters on different chromosomes. The target model was the genus Mus which exhibits a high rate of karyotypic change, a large fraction of which involves centromeres. The chromosomal distribution of rDNA clusters was determined by in situ hybridization of mouse probes in 19 species. Using a molecular-based reference tree, the phylogenetic distribution of clusters within the genus was reconstructed, and the temporal association between rDNA clusters, breakpoints and centromeres was tested by maximum likelihood analyses. Our results highlighted the following features of rDNA cluster dynamics in the genus Mus: i) rDNA clusters showed extensive diversity in number between species and an almost exclusive pericentromeric location, ii) a strong association between rDNA sites and centromeres was retrieved which may be related to their shared constraint of concerted evolution, iii) 24% of the observed breakpoints mapped near an rDNA cluster, and iv) a substantial rate of rDNA cluster change (insertion, deletion) also occurred in the absence of chromosomal rearrangements. This study on the dynamics of rDNA clusters within the genus Mus has revealed a strong evolutionary relationship between rDNA clusters and centromeres. Both of these genomic structures coincide with breakpoints in the genus Mus, suggesting that the accumulation of a large number of repeats in the centromeric region may contribute to the high level of chromosome repatterning observed in this group. However, the elevated rate of rDNA change observed in the chromosomally invariant clade indicates that the presence of these sequences is insufficient to lead to genome instability. In agreement with recent studies, these results suggest that additional factors such as modifications of the epigenetic state of DNA may be required to trigger evolutionary plasticity.