School of Bioscience, University of Kent, UK.
Nucleic Acids Res. 2023 Mar 21;51(5):2319-2332. doi: 10.1093/nar/gkad089.
During mammalian spermatogenesis, the paternal genome is extensively remodelled via replacement of histones with protamines forming the highly compact mature sperm nucleus. Compaction occurs in post-meiotic spermatids and is accompanied by extensive double strand break (DSB) formation. We investigate the epigenomic and genomic context of mouse spermatid DSBs, identifying primary sequence motifs, secondary DNA structures and chromatin contexts associated with this damage. Consistent with previously published results we find spermatid DSBs positively associated with short tandem repeats and LINE elements. We further show spermatid DSBs preferentially occur in association with (CA)n, (NA)n and (RY)n repeats, in predicted Z-DNA, are not associated with G-quadruplexes, are preferentially found in regions of low histone mark coverage and engage the remodelling/NHEJ factor BRD4. Locations incurring DSBs in spermatids also show distinct epigenetic profiles throughout later developmental stages: regions retaining histones in mature sperm, regions susceptible to oxidative damage in mature sperm, and fragile two-cell like embryonic stem cell regions bound by ZSCAN4 all co-localise with spermatid DSBs and with each other. Our results point to a common 'vulnerability code' unifying several types of DNA damage occurring on the paternal genome during reproduction, potentially underpinned by torsional changes during sperm chromatin remodelling.
在哺乳动物精子发生过程中，通过用鱼精蛋白替换组蛋白，父系基因组被广泛重塑，形成高度紧凑的成熟精子核。浓缩发生在减数分裂后精子细胞中，并伴随着广泛的双链断裂 (DSB) 形成。我们研究了小鼠精子细胞 DSB 的表观基因组和基因组背景，确定了与这种损伤相关的主要序列基序、二级 DNA 结构和染色质环境。与先前发表的结果一致，我们发现精子细胞 DSB 与短串联重复序列和 LINE 元件呈正相关。我们进一步表明，精子细胞 DSB 优先与 (CA)n、(NA)n 和 (RY)n 重复序列相关，在预测的 Z-DNA 中，与 G-四链体无关，优先发生在组蛋白标记覆盖度低的区域，并与重塑/NHEJ 因子 BRD4 结合。在精子细胞中发生 DSB 的位置在以后的发育阶段也表现出不同的表观遗传特征：在成熟精子中保留组蛋白的区域、在成熟精子中易受氧化损伤的区域以及由 ZSCAN4 结合的脆弱的两细胞样胚胎干细胞区域都与精子细胞 DSB 以及彼此共定位。我们的研究结果指向一种共同的“脆弱性代码”，它统一了父系基因组在生殖过程中发生的几种类型的 DNA 损伤，其潜在基础可能是精子染色质重塑过程中的扭转变化。
