De La Fuente Rabindranath, Viveiros Maria M, Burns Kathleen H, Adashi Eli Y, Matzuk Martin M, Eppig John J
The Jackson Laboratory, Bar Harbor, ME 04609, USA.
Dev Biol. 2004 Nov 15;275(2):447-58. doi: 10.1016/j.ydbio.2004.08.028.
Global silencing of transcriptional activity in the oocyte genome occurs just before the resumption of meiosis and is a crucial developmental transition at the culmination of oogenesis. Transcriptionally quiescent oocytes rely on stored maternal transcripts to sustain the completion of meiosis, fertilization, and early embryonic cleavage stages. Thus, the timing of silencing is key for successful embryo development. Yet, the cellular and molecular pathways coordinating dynamic changes in large-scale chromatin structure with the onset of transcriptional repression are poorly understood. Here, oocytes obtained from nucleoplasmin 2 knockout (Npm2-/-) mice were used to investigate the relationship between transcriptional repression and chromatin remodeling in the germinal vesicle (GV) of mammalian oocytes. Although temporally linked, global silencing of transcription and chromatin remodeling in the oocyte genome can be experimentally dissociated and therefore must be regulated through distinct pathways. Detection of centromeric heterochromatin DNA sequences with a mouse pan-centromeric chromosome paint revealed that most centromeres are found in close apposition with the nucleolus in transcriptionally quiescent oocytes and therefore constitute an important component of the perinucleolar heterochromatin rim or karyosphere. Pharmacological inhibition of histone deacetylases (HDACs) with trichostatin A (TSA) revealed that HDACs are essential for large-scale chromatin remodeling in the GV. Importantly, the specialized nuclear architecture acquired upon transcriptional repression is essential for meiotic progression as interference with global deacetylation and partial disruption of the karyosphere resulted in a dramatic increase in the proportion of oocytes exhibiting abnormal meiotic chromosome and spindle configuration. These results indicate that the unique chromatin remodeling mechanism in oocytes may be specifically related to meiotic cell division in female mammals.
卵母细胞基因组转录活性的整体沉默发生在减数分裂恢复之前，是卵子发生 culmination 阶段的关键发育转变。转录静止的卵母细胞依靠储存的母体转录本维持减数分裂、受精和早期胚胎分裂阶段的完成。因此，沉默的时间对于胚胎的成功发育至关重要。然而，协调大规模染色质结构动态变化与转录抑制起始的细胞和分子途径却知之甚少。在这里，使用从核质蛋白 2 基因敲除（Npm2-/-）小鼠获得的卵母细胞来研究哺乳动物卵母细胞生发泡（GV）中转录抑制与染色质重塑之间的关系。虽然在时间上相关，但卵母细胞基因组中转录的整体沉默和染色质重塑在实验上可以分离，因此必须通过不同的途径进行调节。用小鼠全着丝粒染色体涂染检测着丝粒异染色质 DNA 序列发现，在转录静止的卵母细胞中，大多数着丝粒与核仁紧密相邻，因此构成核仁周围异染色质边缘或核球的重要组成部分。用曲古抑菌素 A（TSA）对组蛋白去乙酰化酶（HDACs）进行药理学抑制表明，HDACs 对于 GV 中的大规模染色质重塑至关重要。重要的是，转录抑制后获得的特殊核结构对于减数分裂进程至关重要，因为干扰整体去乙酰化和核球的部分破坏导致表现出异常减数分裂染色体和纺锤体构型的卵母细胞比例急剧增加。这些结果表明，卵母细胞中独特的染色质重塑机制可能与雌性哺乳动物的减数分裂细胞分裂特别相关。
