Histone methylation regulates gene expression in the round spermatids to set the RNA payloads of sperm

Gene expression during spermatogenesis undergoes significant changes due to a demanding sequence of mitosis, meiosis and differentiation. Round spermatids have to prepare for DNA condensation as well as synthesize transcripts of genes required for the differentiation process. However, the mechanisms of gene activation and silencing in round spermatids remain largely unknown. We employed ChIP-seq to figure out the correlation of H3K4me3 and H3K9me3 marks with transcriptional activation and silencing in round spermatids. Out of about 2800 genes identified by H3K4me3 chipseq, transcriptome sequencing in purified round spermatids showed the presence of transcripts corresponding to about 64% of the genes. On the other hand, only about 25% of H3K9me3 enriched genes showed transcription in round spermatids, that too at very low levels. In conclusion, H3K4me3 enrichment in round spermatids correlates significantly with gene expression and H3K9me3 correlates with gene silencing, both of which are equally important for successful spermatogenesis. Performed ChIP-Seq analysis of H3K4me3 and H3K9me3 in rat round spermatids.

精子发生过程中，由于有丝分裂、减数分裂与细胞分化的严苛时序进程，基因表达会发生显著改变。圆形精子细胞需要为DNA凝缩做好准备，并合成分化过程所需基因的转录本。然而，圆形精子细胞中基因激活与沉默的调控机制在很大程度上仍未被阐明。本研究采用染色质免疫共沉淀测序（ChIP-seq）技术，探究圆形精子细胞中H3K4me3与H3K9me3修饰标记与转录激活、沉默之间的关联。经H3K4me3 ChIP-seq鉴定的约2800个基因中，对纯化后圆形精子细胞的转录组测序结果显示，其中约64%的基因存在对应转录本。另一方面，在H3K9me3富集的基因中，仅约25%在圆形精子细胞中存在转录，且转录水平极低。综上，圆形精子细胞中H3K4me3富集与基因表达显著相关，而H3K9me3则与基因沉默相关，二者对于精子发生的顺利完成均具有同等重要的作用。本研究在大鼠圆形精子细胞中开展了H3K4me3与H3K9me3的ChIP-seq分析。