Muller’s ratchet of the Y chromosome with gene conversion
Muller’s ratchet of the Y chromosome with gene conversion
复制标题
Y染色体穆勒棘轮与基因转换
DOI：
10.1093/genetics/iyab204
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发表时间：
2022
期刊：
影响因子：
3.3
通讯作者：
Innan Hideki
中科院分区：
文献类型：
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作者：
Sakamoto Takahiro;Innan Hideki
米勒棘轮是一个过程，其中有害突变在没有重组的情况下被不可逆地固定。Y染色体的退化及其基因的逐渐丢失可以用穆勒的棘轮来解释。然而，大多数理论考虑的是单拷贝基因，可能不适用于Y染色体，因为Y染色体在许多物种中有许多重复的基因，它们可能正在通过基因转换进行协同进化。我们开发了一个穆勒棘轮模型来探索Y染色体的进化。该模型假设一个nonrecombining染色体与单拷贝和重复的基因。我们使用分析和模拟的方法来获得在这个模型中的基因丢失率，特别注意的基因转换的作用。通过基因转换进行的均质化使两个重复的拷贝要么突变要么完整。前者促进棘轮，后者阻碍棘轮，我们要问的是，在何种条件下，哪种反作用力占主导地位。我们发现，基因转换的影响是复杂的，并依赖于基因复制的适应性效应。当复制对适应性没有影响时，基因转换会加速单拷贝和复制基因的棘轮。如果复制具有加性适应性效应，那么无论基因转换率如何，基因复制都会加速单拷贝基因的棘轮效应，而基因转换则会减缓复制基因的退化。我们的研究结果表明，Y染色体的进化涉及几个参数，包括基因复制的健身效果，通过增加剂量和基因转换率。
Muller’s ratchet is a process in which deleterious mutations are fixed irreversibly in the absence of recombination. The degeneration of the Y chromosome, and the gradual loss of its genes, can be explained by Muller’s ratchet. However, most theories consider single-copy genes, and may not be applicable to Y chromosomes, which have a number of duplicated genes in many species, which are probably undergoing concerted evolution by gene conversion. We developed a model of Muller’s ratchet to explore the evolution of the Y chromosome. The model assumes a nonrecombining chromosome with both single-copy and duplicated genes. We used analytical and simulation approaches to obtain the rate of gene loss in this model, with special attention to the role of gene conversion. Homogenization by gene conversion makes both duplicated copies either mutated or intact. The former promotes the ratchet, and the latter retards, and we ask which of these counteracting forces dominates under which conditions. We found that the effect of gene conversion is complex, and depends upon the fitness effect of gene duplication. When duplication has no effect on fitness, gene conversion accelerates the ratchet of both single-copy and duplicated genes. If duplication has an additive fitness effect, the ratchet of single-copy genes is accelerated by gene duplication, regardless of the gene conversion rate, whereas gene conversion slows the degeneration of duplicated genes. Our results suggest that the evolution of the Y chromosome involves several parameters, including the fitness effect of gene duplication by increasing dosage and gene conversion rate.