Institute of Animal Science, CZ 104 01 Prague, Czech Republic.
Development. 2014 Apr;141(8):1694-704. doi: 10.1242/dev.105940.
The oocyte (maternal) nucleolus is essential for early embryonic development and embryos originating from enucleolated oocytes arrest at the 2-cell stage. The reason for this is unclear. Surprisingly, RNA polymerase I activity in nucleolus-less mouse embryos, as manifested by pre-rRNA synthesis, and pre-rRNA processing are not affected, indicating an unusual role of the nucleolus. We report here that the maternal nucleolus is indispensable for the regulation of major and minor satellite repeats soon after fertilisation. During the first embryonic cell cycle, absence of the nucleolus causes a significant reduction in major and minor satellite DNA by 12% and 18%, respectively. The expression of satellite transcripts is also affected, being reduced by more than half. Moreover, extensive chromosome bridging of the major and minor satellite sequences was observed during the first mitosis. Finally, we show that the absence of the maternal nucleolus alters S-phase dynamics and causes abnormal deposition of the H3.3 histone chaperone DAXX in pronuclei of nucleolus-less zygotes.
卵母细胞（母体）核仁对于早期胚胎发育至关重要，而去核卵母细胞来源的胚胎在 2 细胞阶段停滞。其原因尚不清楚。令人惊讶的是，无核仁小鼠胚胎中的 RNA 聚合酶 I 活性（表现为前 rRNA 合成）和前 rRNA 加工不受影响，这表明核仁具有不寻常的作用。我们在这里报告，母体核仁对于受精后主要和次要卫星重复序列的调控是必不可少的。在第一个胚胎细胞周期中，核仁的缺失导致主要和次要卫星 DNA 分别减少 12%和 18%。卫星转录本的表达也受到影响，减少了一半以上。此外，在第一次有丝分裂过程中观察到主要和次要卫星序列的广泛染色体桥接。最后，我们表明，缺乏母体核仁会改变 S 期动力学，并导致 H3.3 组蛋白伴侣 DAXX 在无核仁合子的原核中异常沉积。
