Pazhayam Nila M, Sagar Sasha, Sekelsky Jeff
Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.
Department of Psychology and Neuroscience, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.
bioRxiv. 2024 Dec 20:2024.12.19.629512. doi: 10.1101/2024.12.19.629512.
The centromere effect (CE) is a meiotic phenomenon that ensures meiotic crossover suppression in pericentromeric regions. Despite being a critical safeguard against nondisjunction, the mechanisms behind the CE remain unknown. Previous studies have shown that various regions of the pericentromere, encompassing proximal euchromatin, beta and alpha heterochromatin, undergo varying levels of crossover suppression, raising the question of whether distinct mechanisms establish the CE in these different regions. To address this question, we asked whether different pericentromeric regions respond differently to mutations that impair various features that may play a role in the CE. In flies with a mutation that affects the synaptonemal complex (SC), a structure is hypothesized to have important roles in recombination and crossover patterning, we observed a significant redistribution of pericentromeric crossovers from proximal euchromatin towards beta heterochromatin but not alpha heterochromatin, indicating a role for the SC in suppressing crossovers in beta heterochromatin. In flies mutant for or , which encode components of a critical pro-crossover complex, there was a more extreme redistribution of pericentromeric crossovers towards both beta and alpha heterochromatin, suggesting an important role for these meiotic recombination factors in suppressing heterochromatic crossovers. Lastly, we mapped crossovers in flies mutant for . Although we expected a strong alleviation of crossover suppression in heterochromatic regions, no changes in pericentromeric crossover distribution were observed in this mutant, indicating that this vital heterochromatin factor is dispensable to prevent crossovers in heterochromatin. Our results indicate that the meiotic machinery plays a bigger role in suppressing crossovers than the chromatin state.
着丝粒效应（CE）是一种减数分裂现象，可确保在着丝粒周围区域抑制减数分裂交叉互换。尽管它是防止染色体不分离的关键保障，但CE背后的机制仍不清楚。先前的研究表明，着丝粒周围的各个区域，包括近端常染色质、β和α异染色质，经历不同程度的交叉互换抑制，这就提出了一个问题，即在这些不同区域建立CE的机制是否不同。为了解决这个问题，我们研究了不同的着丝粒周围区域对影响可能在CE中起作用的各种特征的突变是否有不同反应。在果蝇中，有一种突变影响联会复合体（SC），据推测该结构在重组和交叉互换模式中起重要作用，我们观察到着丝粒周围交叉互换从近端常染色质向β异染色质显著重新分布，但α异染色质没有，这表明SC在抑制β异染色质中的交叉互换中起作用。在编码关键的促进交叉互换复合体成分的 或 突变的果蝇中，着丝粒周围交叉互换向β和α异染色质都有更极端的重新分布，这表明这些减数分裂重组因子在抑制异染色质交叉互换中起重要作用。最后，我们在 突变的果蝇中绘制了交叉互换图谱。尽管我们预计异染色质区域的交叉互换抑制会大大减轻，但在该突变体中未观察到着丝粒周围交叉互换分布的变化，这表明这种重要的异染色质因子对于防止异染色质中的交叉互换是可有可无的。我们的结果表明，减数分裂机制在抑制交叉互换中比染色质状态起更大的作用。
