Purifying Selection Maintains Dosage-Sensitive Genes during Degeneration of the Threespine Stickleback Y Chromosome.
Purifying Selection Maintains Dosage-Sensitive Genes during Degeneration of the Threespine Stickleback Y Chromosome.
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纯化选择在三刺鱼 Y 染色体变性过程中维持剂量敏感基因。
DOI：
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发表时间：
2015
影响因子：
10.7
通讯作者：
C. L. Peichel
中科院分区：
文献类型：
--
作者：
M. White;J. Kitano;C. L. Peichel
性染色体受到独特的进化力量抑制重组，导致序列退化，形成异型染色体对（即XY或ZW）。尽管在描述脊椎动物性染色体的这些进化过程的结果方面已经取得了进展，但人们仍然不清楚重组抑制和序列分化通常是如何发生的，以及基因剂量失衡是如何在异配子性别中解决的。三刺棘鱼（Gasterosteus aculeatus）在分化较早的阶段就拥有一对XY性染色体，是探索脊椎动物性染色体进化的有力模型系统。使用全基因组和转录组测序的组合，我们表征序列进化和基因表达跨性染色体。我们发现了两个不同的进化层，它们与Y染色体上已知的结构重排相对应。在最古老的地层中，只剩下少数基因，这些基因处于强烈的净化选择之下。通过比较外群中性别连锁基因表达与常染色体同源基因的表达，我们发现三刺鱼的剂量补偿并未通过雄性X染色体的上调而进化。相反，在最古老的地层中，仍然拥有Y染色体等位基因的基因在哺乳动物和酵母中被预测为剂量敏感的基因所富集。我们的研究结果表明，通过强净化选择保留Y染色体等位基因的功能，可以避免单倍不足基因的剂量不平衡。
Sex chromosomes are subject to unique evolutionary forces that cause suppression of recombination, leading to sequence degeneration and the formation of heteromorphic chromosome pairs (i.e., XY or ZW). Although progress has been made in characterizing the outcomes of these evolutionary processes on vertebrate sex chromosomes, it is still unclear how recombination suppression and sequence divergence typically occur and how gene dosage imbalances are resolved in the heterogametic sex. The threespine stickleback fish (Gasterosteus aculeatus) is a powerful model system to explore vertebrate sex chromosome evolution, as it possesses an XY sex chromosome pair at relatively early stages of differentiation. Using a combination of whole-genome and transcriptome sequencing, we characterized sequence evolution and gene expression across the sex chromosomes. We uncovered two distinct evolutionary strata that correspond with known structural rearrangements on the Y chromosome. In the oldest stratum, only a handful of genes remain, and these genes are under strong purifying selection. By comparing sex-linked gene expression with expression of autosomal orthologs in an outgroup, we show that dosage compensation has not evolved in threespine sticklebacks through upregulation of the X chromosome in males. Instead, in the oldest stratum, the genes that still possess a Y chromosome allele are enriched for genes predicted to be dosage sensitive in mammals and yeast. Our results suggest that dosage imbalances may have been avoided at haploinsufficient genes by retaining function of the Y chromosome allele through strong purifying selection.
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影响因子：
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作者：
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