Department of Animal Science, McGill University, Sainte-Anne-de-Bellevue, Quebec, Canada.
Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada.
Biol Reprod. 2019 Jun 1;100(6):1661-1672. doi: 10.1093/biolre/ioz055.
Environmental exposures can alter the long-term health and development of offspring. How this environmental information is transmitted via the germline remains unknown, but it is thought to involve epigenetic inheritance. We recently determined that genetic disruption of histone H3 di-methylation at lysine 4 (H3K4me2) in sperm alters gene expression in the embryo and negatively impacts development across generations. However, little is known regarding when in spermatogenesis H3K4me2 methylation is established, and whether specific regions bearing H3K4me2 resist the epigenome remodeling that occurs throughout spermatogenesis. Our objective was to determine what genomic regions bearing histone H3K4me2 in spermatogonia are also present in sperm. Methods: Using transgenic mice expressing Oct4-GFP, we isolated an enriched spermatogonia population and performed ChIP-seq for H3K4me2, followed by downstream bioinformatics analysis. Using our epigenomic data and existing datasets, we compared the genomic distribution of H3K4me2 between spermatogonia and sperm. We also assessed the expression level of genes enriched in H3K4me2 in spermatogenic cell types and at specific embryonic developmental time-points. We observed that many regions of the sperm epigenome bearing H3K4me2 are already present in spermatogonia, suggesting an early establishment of this histone mark in spermatogenesis. Subsets of genes with a high enrichment in H3K4me2 in sperm are strongly expressed in spermatogenesis and others are associated with high gene expression during embryo development. These findings suggest that if epimutations in H3K4me2 are induced in spermatogonia they have the possibility to persist throughout spermatogenesis and may influence fertility by altering gene expression in spermatogenesis and in the embryo.
环境暴露会改变后代的长期健康和发育。这种环境信息如何通过生殖系传递尚不清楚，但据认为涉及表观遗传遗传。我们最近确定，精子中组蛋白 H3 赖氨酸 4 二甲基化（H3K4me2）的遗传破坏会改变胚胎中的基因表达，并在代际间对发育产生负面影响。然而，对于精子发生中何时建立 H3K4me2 甲基化，以及是否存在特定区域带有 H3K4me2 抵抗整个精子发生过程中发生的表观基因组重塑，知之甚少。我们的目标是确定在精原细胞中带有组蛋白 H3K4me2 的哪些基因组区域也存在于精子中。
使用表达 Oct4-GFP 的转基因小鼠，我们分离出富含精原细胞的群体，并进行 H3K4me2 的 ChIP-seq，然后进行下游生物信息学分析。利用我们的表观基因组数据和现有数据集，我们比较了精原细胞和精子中 H3K4me2 的基因组分布。我们还评估了在特定胚胎发育时间点富含 H3K4me2 的基因在精子发生细胞类型中的表达水平。
我们观察到，精子表观基因组中带有 H3K4me2 的许多区域已经存在于精原细胞中，这表明这种组蛋白标记在精子发生中很早就建立了。在精子中 H3K4me2 高度富集的基因子集在精子发生中强烈表达，而其他基因则与胚胎发育过程中的高基因表达相关。这些发现表明，如果 H3K4me2 中的 epimutations 在精原细胞中诱导，它们有可能在整个精子发生过程中持续存在，并通过改变精子发生和胚胎中的基因表达来影响生育能力。
