Developmental Origins of Transgenerational Sperm Histone Retention Following Ancestral Exposures

This study was designed to investigate the developmental origins of the transgenerational differential histone retention sites (called DHRs) during gametogenesis of the sperm. Vinclozolin and DDT were independently used to promote the epigenetic transgenerational inheritance of these DHRs. Male control, DDT lineage and vinclozolin lineage F3 generation rats were used to isolate round spermatids, caput epididymal spermatozoa, and caudal sperm. The DHRs between the control versus DDT lineage or vinclozolin lineage were determined in these three developmental stages. DHRs and a reproducible core of histone H3 retention sites were observed using an H3 chromatin immunoprecipitation (ChIP-Seq) analysis in the germ cell populations. The chromosomal locations and genomic features of the DHRs were also analyzed. A cascade of epigenetic histone retention site alterations was found to be initiated in or prior to the round spermatids that is further altered during epididymal sperm maturation. Observations show that in addition to alterations in sperm DNA methylation previously identified, the induction of differential histone retention sites (DHRs) in the later stages of spermatogenesis also occurs.本研究旨在探究精子发生过程中跨代差异组蛋白保留位点（transgenerational differential histone retention sites, DHRs）的发育起源。本研究分别使用烯菌酮（vinclozolin）与滴滴涕（DDT），诱导上述DHRs的表观遗传跨代遗传。选取雄性对照组、滴滴涕谱系组与烯菌酮谱系组的F3代大鼠，分离其圆形精子细胞、附睾头精子与附睾尾精子。在上述三个发育阶段中，分别分析对照组与滴滴涕谱系组、对照组与烯菌酮谱系组之间的DHRs差异。通过组蛋白H3染色质免疫共沉淀测序（chromatin immunoprecipitation sequencing, ChIP-Seq）分析，在生殖细胞群体中检测到了DHRs以及一组可重复的组蛋白H3保留位点核心集。本研究同时分析了DHRs的染色体定位与基因组特征。研究发现，一系列表观遗传组蛋白保留位点改变的级联反应可在圆形精子细胞阶段或更早启动，并在精子附睾成熟过程中进一步发生变化。研究结果表明，除此前已报道的精子DNA甲基化改变外，在精子发生后期也可诱导产生DHRs。