Chromosomal fusions represent one of the most common types of chromosomal rearrangements found in nature. Yet, their role in shaping the genomic landscape of recombination and hence genome evolution remains largely unexplored. Here, we take advantage of wild mice populations with chromosomal fusions to evaluate the effect of this type of structural variant on genomic landscapes of recombination and divergence. To this aim, we combined cytological analysis of meiotic crossovers (COs) in primary spermatocytes with inferred analysis of recombination rates based on linkage disequilibrium using single nucleotide polymorphisms. Our results suggest the presence of a combined effect of Rb fusions and Prdm9 allelic background, a gene involved in the formation of meiotic double strand breaks and postzygotic reproductive isolation, in reshaping genomic landscapes of recombination. We detected a chromosomal redistribution of meiotic recombination towards telomeric regions in metacentric chromosomes in mice with Robertsonian (Rb) fusions when compared to non-fused mice. This repatterning was accompanied by increased levels of CO interference and reduced levels of estimated recombination rates between populations, together with high levels of genomic divergence. Interestingly, we detected that Prdm9 allelic background was a major determinant of recombination rates at the population level, whereas Rb fusions showed limited effects, restricted to centromeric regions of fused chromosomes. Altogether, our results provide new insights into the effect of Rb fusions and Prdm9 background on meiotic recombination.

中文翻译：

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野生家鼠群体重组和基因组分歧的多重基因组景观 - 染色体融合和 Prdm9 的作用

染色体融合代表自然界中最常见的染色体重排类型之一。然而，它们在塑造重组基因组景观以及基因组进化方面的作用在很大程度上仍未被探索。在这里，我们利用具有染色体融合的野生小鼠群体来评估这种类型的结构变异对重组和分化的基因组景观的影响。为此，我们将原代精母细胞减数分裂交换（CO）的细胞学分析与基于连锁不平衡的重组率推断分析结合起来，使用单核苷酸多态性。我们的结果表明，Rb 融合和 Prdm9 等位基因背景（一种参与减数分裂双链断裂和合子后生殖隔离形成的基因）在重塑重组基因组景观中存在联合效应。与非融合小鼠相比，我们在罗伯逊 (Rb) 融合小鼠的定着丝粒染色体中检测到减数分裂重组向端粒区域的染色体重新分布。这种重新模式伴随着CO干扰水平的增加和群体之间估计重组率水平的降低，以及高水平的基因组分歧。有趣的是，我们发现 Prdm9 等位基因背景是群体水平重组率的主要决定因素，而 Rb 融合显示出有限的影响，仅限于融合染色体的着丝粒区域。总而言之，我们的结果为 Rb 融合和 Prdm9 背景对减数分裂重组的影响提供了新的见解。