From the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine and.
Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, College of Life Science, Northeast Agricultural University, Harbin 150030, China, and.
J Biol Chem. 2018 Mar 9;293(10):3829-3838. doi: 10.1074/jbc.RA117.001150. Epub 2018 Jan 22.
Derepression of chromatin-mediated transcriptional repression of paternal and maternal genomes is considered the first major step that initiates zygotic gene expression after fertilization. The histone variant H3.3 is present in both male and female gametes and is thought to be important for remodeling the paternal and maternal genomes for activation during both fertilization and embryogenesis. However, the underlying mechanisms remain poorly understood. Using our H3.3B-HA-tagged mouse model, engineered to report H3.3 expression in live animals and to distinguish different sources of H3.3 protein in embryos, we show here that sperm-derived H3.3 (sH3.3) protein is removed from the sperm genome shortly after fertilization and extruded from the zygotes via the second polar bodies (PBII) during embryogenesis. We also found that the maternal H3.3 (mH3.3) protein is incorporated into the paternal genome as early as 2 h postfertilization and is detectable in the paternal genome until the morula stage. Knockdown of maternal H3.3 resulted in compromised embryonic development both of fertilized embryos and of androgenetic haploid embryos. Furthermore, we report that mH3.3 depletion in oocytes impairs both activation of the pluripotency marker gene and global transcription from the paternal genome important for early embryonic development. Our results suggest that H3.3-mediated paternal chromatin remodeling is essential for the development of preimplantation embryos and the activation of the paternal genome during embryogenesis.
染色质介导的父本和母本基因组转录抑制的去抑制被认为是受精后启动合子基因表达的第一个主要步骤。组蛋白变体 H3.3 存在于雄性和雌性配子中，被认为对于在受精和胚胎发生过程中激活父本和母本基因组的重塑很重要。然而，其潜在的机制仍知之甚少。使用我们的 H3.3B-HA 标记的小鼠模型，该模型旨在报告活体动物中的 H3.3 表达，并区分胚胎中不同来源的 H3.3 蛋白，我们在这里表明，精子衍生的 H3.3（sH3.3）蛋白在受精后不久就从精子基因组中被去除，并在胚胎发生过程中通过第二极体（PBII）从受精卵中挤出。我们还发现，母本 H3.3（mH3.3）蛋白早在受精后 2 小时就被整合到父本基因组中，并可在父本基因组中检测到，直到桑葚胚阶段。母本 H3.3 的敲低导致受精胚胎和雄核单倍体胚胎的胚胎发育受损。此外，我们报告说，卵母细胞中 mH3.3 的耗竭会损害多能性标记基因的激活和对早期胚胎发育很重要的父本基因组的全局转录。我们的结果表明，H3.3 介导的父本染色质重塑对于植入前胚胎的发育和胚胎发生过程中父本基因组的激活至关重要。
