Irani Delna, Arya Deepshikha, Tandon Deepti, Bansal Vandana, Patil Anushree, Singh Dipty
Department of Neuroendocrinology, ICMR-National Institute for Research in Reproductive and Child Health, Mumbai, India.
Department of Clinical Research, ICMR-National Institute for Research in Reproductive and Child Health, Mumbai, India.
Epigenetics. 2025 Dec;20(1):2498859. doi: 10.1080/15592294.2025.2498859. Epub 2025 Apr 29.
During fertilization, spermatozoa contribute genetic and epigenetic factors such as chromatin packaged with protamines and histones; DNA methylome, non-coding RNAs, etc. Human sperm chromatin retains 5-15% nucleosomes which can play a key role in embryonic development. Recurrent pregnancy loss (RPL) is a condition mainly attributed to defects in embryo and placenta development. Majority of the known RPL factors are of maternal contribution, while ~50% RPL cases are termed idiopathic (iRPL). In addition to paternal genetic factors, epigenetic factors via sperm could also be responsible for iRPL. Hence, we investigated alterations in retained nucleosome content of iRPL sperm ( = 46) as compared to fertile male population ( = 40). We measured the relative abundance of core histone H4 and Protamine-2 content along with the modified histones H4Ac, H3K4me3, H3K27me3 and H3K9me3 by flow cytometry. H4 and Protamine-2 levels were comparable in both groups and showed significant negative correlation. The iRPL group had significantly higher levels of sperm H3K4me3 as compared to the fertile control group. The other modified histones and protamine levels showed no significant alterations. Furthermore, sperm DFI was found to be significantly positively correlated with H4 levels in both groups. No significant correlation was observed between sperm 5-mC levels with H4 and other modified histone levels. A fraction of H3K4me3 enrichment is now known to resist embryonic epigenetic reprogramming; and hence, such elevated levels in the sperm would question its developmental competence leading to RPL pathology. Also, incidence of sperm DNA fragmentation is associated with increased histone retention in both fertile and iRPL cases.
在受精过程中，精子会贡献遗传和表观遗传因子，如与鱼精蛋白和组蛋白包装在一起的染色质；DNA甲基化组、非编码RNA等。人类精子染色质保留5%-15%的核小体，这些核小体在胚胎发育中起关键作用。复发性流产（RPL）是一种主要归因于胚胎和胎盘发育缺陷的病症。大多数已知的RPL因素来自母体，而约50%的RPL病例被称为特发性（iRPL）。除了父系遗传因素外，通过精子传递的表观遗传因素也可能导致iRPL。因此，我们研究了与可育男性群体（n = 40）相比，iRPL精子（n = 46）中保留的核小体含量的变化。我们通过流式细胞术测量了核心组蛋白H4和鱼精蛋白-2的相对丰度，以及修饰后的组蛋白H4Ac、H3K4me3、H3K27me3和H3K9me3。两组的H4和鱼精蛋白-2水平相当，且呈显著负相关。与可育对照组相比，iRPL组精子H3K4me3水平显著更高。其他修饰后的组蛋白和鱼精蛋白水平无显著变化。此外，发现两组精子DNA碎片指数（DFI）与H4水平均呈显著正相关。未观察到精子5-甲基胞嘧啶（5-mC）水平与H4及其他修饰后的组蛋白水平之间存在显著相关性。现在已知一部分H3K4me3富集能够抵抗胚胎表观遗传重编程；因此，精子中如此高的水平会质疑其发育能力，导致RPL病理。此外，在可育和iRPL病例中，精子DNA碎片化的发生率都与组蛋白保留增加有关。
