Centre for Genetics and Genomics, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom ; Systems Biology of Gene Regulatory Elements, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
Department of Biology, McGill University, Montréal, Québec, Canada ; Department of Biology, Concordia University, Montreal, Québec, Canada.
PLoS Genet. 2013;9(12):e1004003. doi: 10.1371/journal.pgen.1004003. Epub 2013 Dec 19.
Post-transcriptional regulatory mechanisms are of fundamental importance to form robust genetic networks, but their roles in stem cell pluripotency remain poorly understood. Here, we use freshwater planarians as a model system to investigate this and uncover a role for CCR4-NOT mediated deadenylation of mRNAs in stem cell differentiation. Planarian adult stem cells, the so-called neoblasts, drive the almost unlimited regenerative capabilities of planarians and allow their ongoing homeostatic tissue turnover. While many genes have been demonstrated to be required for these processes, currently almost no mechanistic insight is available into their regulation. We show that knockdown of planarian Not1, the CCR4-NOT deadenylating complex scaffolding subunit, abrogates regeneration and normal homeostasis. This abrogation is primarily due to severe impairment of their differentiation potential. We describe a stem cell specific increase in the mRNA levels of key neoblast genes after Smed-not1 knock down, consistent with a role of the CCR4-NOT complex in degradation of neoblast mRNAs upon the onset of differentiation. We also observe a stem cell specific increase in the frequency of longer poly(A) tails in these same mRNAs, showing that stem cells after Smed-not1 knock down fail to differentiate as they accumulate populations of transcripts with longer poly(A) tails. As other transcripts are unaffected our data hint at a targeted regulation of these key stem cell mRNAs by post-transcriptional regulators such as RNA-binding proteins or microRNAs. Together, our results show that the CCR4-NOT complex is crucial for stem cell differentiation and controls stem cell-specific degradation of mRNAs, thus providing clear mechanistic insight into this aspect of neoblast biology.
转录后调控机制对形成稳健的遗传网络至关重要，但它们在干细胞多能性中的作用仍知之甚少。在这里，我们使用淡水涡虫作为模型系统来研究这一点，并揭示了 CCR4-NOT 介导的 mRNA 脱腺苷酸化在干细胞分化中的作用。涡虫成体干细胞，即所谓的成体神经干细胞，驱动涡虫几乎无限的再生能力，并允许其持续的体内组织更新。虽然已经证明许多基因对于这些过程是必需的，但目前几乎没有关于它们调控的机制见解。我们表明，敲低涡虫 Not1（CCR4-NOT 脱腺苷酸化复合物支架亚基）会破坏再生和正常的体内平衡。这种破坏主要是由于它们的分化潜力严重受损。我们描述了 Smed-not1 敲低后关键成体神经干细胞基因的 mRNA 水平出现特异性增加，这与 CCR4-NOT 复合物在分化开始时降解成体神经干细胞 mRNA 的作用一致。我们还观察到这些相同 mRNA 中的长 poly(A)尾巴的频率在成体神经干细胞中特异性增加，表明 Smed-not1 敲低后的成体神经干细胞未能分化，因为它们积累了具有更长 poly(A)尾巴的转录本。由于其他转录本不受影响，我们的数据暗示这些关键成体神经干细胞 mRNA 受到 RNA 结合蛋白或 microRNAs 等转录后调节剂的靶向调控。总之，我们的结果表明 CCR4-NOT 复合物对于干细胞分化至关重要，并控制着特定于干细胞的 mRNA 降解，从而为成体神经干细胞生物学的这一方面提供了明确的机制见解。
