Initiation of recombination suppression and PAR formation during the early stages of neo-sex chromosome differentiation in the Okinawa spiny rat, Tokudaia muenninki.
Initiation of recombination suppression and PAR formation during the early stages of neo-sex chromosome differentiation in the Okinawa spiny rat, Tokudaia muenninki.
复制标题
DOI：
10.1186/s12862-015-0514-y
复制
发表时间：
2015-10-29
影响因子：
3.4
通讯作者：
Kuroiwa A
中科院分区：
文献类型：
--
作者：
Murata C;Kuroki Y;Imoto I;Tsukahara M;Ikejiri N;Kuroiwa A
现存真兽类物种的性染色体太古老，无法揭示启动性染色体分化的过程。相比之下，由新近起源的性-常染色体融合产生的新性染色体预计在进化上是年轻的，因此为阐明真核生物性染色体进化的早期阶段提供了一个很好的模式。在这里，我们描述了木麻黄在新性染色体分化过程中的基因组进化。使用50个BAC克隆作为探针的FISH图谱显示，在新的性染色体之间没有染色体重排。替换方向分析表明，与重组活性呈正相关的富含GC的序列发生在新性染色体的周边区，而不是中间区。相反，在这些着丝粒周围区域观察到了向AT富集区的序列进化。此外，我们通过对多个男性和女性的基因测序检测男性特有的替换，以及每个新性别衍生的BAC序列，显示了着丝粒周围区域之间的遗传分化以及neo-Y区域的加速进化速度。我们的结果表明，在没有染色体重排的情况下，重组在新性别染色体的着丝粒周围区域被抑制，而在几乎未分化的新性别染色体的染色体周围区域，高水平的重组活性是有限的。我们认为，在性染色体分化的早期，PAR可能是作为一种独立于重组抑制扩散的事件在性染色体的端粒周围区域形成的。本文的在线版本(doi：10.1186/s12862-0150514-y)包含补充材料，授权用户可以使用。
Sex chromosomes of extant eutherian species are too ancient to reveal the process that initiated sex-chromosome differentiation. By contrast, the neo-sex chromosomes generated by sex-autosome fusions of recent origin in Tokudaia muenninki are expected to be evolutionarily ‘young’, and therefore provide a good model in which to elucidate the early phases of eutherian sex chromosome evolution. Here we describe the genomic evolution of T. muenninki in neo-sex chromosome differentiation. FISH mapping of a T. muenninki male, using 50 BAC clones as probes, revealed no chromosomal rearrangements between the neo-sex chromosomes. Substitution-direction analysis disclosed that sequence evolution toward GC-richness, which positively correlates with recombination activity, occurred in the peritelomeric regions, but not middle regions of the neo-sex chromosomes. In contrast, the sequence evolution toward AT-richness was observed in those pericentromeric regions. Furthermore, we showed genetic differentiation between the pericentromeric regions as well as an accelerated rate of evolution in the neo-Y region through the detection of male-specific substitutions by gene sequencing in multiple males and females, and each neo-sex–derived BAC sequencing. Our results suggest that recombination has been suppressed in the pericentromeric region of neo-sex chromosomes without chromosome rearrangement, whereas high levels of recombination activity is limited in the peritelomeric region of almost undifferentiated neo-sex chromosomes. We conclude that PAR might have been formed on the peritelomeric region of sex chromosomes as an independent event from spread of recombination suppression during the early stages of sex chromosome differentiation. The online version of this article (doi:10.1186/s12862-015-0514-y) contains supplementary material, which is available to authorized users.