Dnmt3a Regulates Proliferation of Muscle Satellite Cells via p57Kip2.
Dnmt3a Regulates Proliferation of Muscle Satellite Cells via p57Kip2.
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DOI：
10.1371/journal.pgen.1006167
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发表时间：
2016-07
期刊：
影响因子：
4.5
通讯作者：
Asahara H
中科院分区：
文献类型：
--
作者：
Naito M;Mori M;Inagawa M;Miyata K;Hashimoto N;Tanaka S;Asahara H
细胞分化状态由基因表达谱决定，并受表观遗传机制的协调控制。细胞类型特异性的DNA甲基化模式是由染色质修饰剂建立的，包括从头DNA甲基转移酶，如Dnmt3a和Dnmt3b。自肌源性主控基因MyoD被发现以来，肌源性分化已被用作研究组织分化的模型系统。虽然关于肌源性基因网络的知识正在积累，但对DNA甲基化如何控制肌源性基因程序的理解有限。为了阐明DNA甲基化在肌肉发育和再生中的作用，我们研究了小鼠肌肉前体细胞Dnmt3a突变的后果。Pax3启动子驱动的dnmt3a条件敲除（cKO）小鼠在骨骼肌中表现出器官质量下降，心脏毒素诱导的肌肉损伤后再生减弱。此外，Dnmt3a-null卫星细胞（SCs）在培养中表现出显著的增殖丧失。转录组分析显示，在Dnmt3a-KO sc中，周期蛋白依赖性激酶抑制剂（CDKIs）的Cip/Kip家族成员p57Kip2表达异常。此外，rnai介导的p57Kip2的缺失补充了SC的增殖活性，从而确立了Dnmt3a-p57Kip2轴在SC增殖调控中的作用。与这些发现一致，Dnmt3a-cKO肌肉表现出较少的Pax7+ SCs，这表明p57Kip2蛋白的表达增加。因此，发现Dnmt3a通过p57Kip2通过表观遗传调节SCs的增殖来维持肌肉稳态。肌肉的内稳态是如何维持的还没有完全阐明。表观遗传疾病，如导致骨骼肌过度生长和横纹肌肉瘤的贝克威斯-维德曼综合征，表明表观遗传调控，如DNA甲基化，有助于这种体内平衡控制。DNA甲基化是由DNA甲基转移酶介导的，如Dnmt3a和Dnmt3b，它们是新生的DNA甲基转移酶。DNA甲基化在体细胞干细胞中的作用尚不完全清楚，尽管它已被证明在原始生殖细胞和胚胎干细胞的分化中不可或缺。在本报告中，我们通过分析Dnmt3a条件敲除（cKO）小鼠，研究了Dnmt3a在肌肉卫星细胞中的作用。在cKO小鼠中，Dnmt3a基因座被肌肉前体系中特异性激活的Pax7或Pax3启动子驱动的Cre-recombinase删除。cKO小鼠中Dnmt3a的缺失导致肌肉质量下降和肌肉再生明显受损。此外，Dnmt3a的缺失还会导致SCs的增殖能力显著下降，这是由细胞周期蛋白依赖性激酶抑制剂p57Kip2的错误表达引起的。因此，我们的研究结果表明DNA甲基化在肌肉稳态中起着至关重要的作用。
Cell differentiation status is defined by the gene expression profile, which is coordinately controlled by epigenetic mechanisms. Cell type-specific DNA methylation patterns are established by chromatin modifiers including de novo DNA methyltransferases, such as Dnmt3a and Dnmt3b. Since the discovery of the myogenic master gene MyoD, myogenic differentiation has been utilized as a model system to study tissue differentiation. Although knowledge about myogenic gene networks is accumulating, there is only a limited understanding of how DNA methylation controls the myogenic gene program. With an aim to elucidate the role of DNA methylation in muscle development and regeneration, we investigate the consequences of mutating Dnmt3a in muscle precursor cells in mice. Pax3 promoter-driven Dnmt3a-conditional knockout (cKO) mice exhibit decreased organ mass in the skeletal muscles, and attenuated regeneration after cardiotoxin-induced muscle injury. In addition, Dnmt3a-null satellite cells (SCs) exhibit a striking loss of proliferation in culture. Transcriptome analysis reveals dysregulated expression of p57Kip2, a member of the Cip/Kip family of cyclin-dependent kinase inhibitors (CDKIs), in the Dnmt3a-KO SCs. Moreover, RNAi-mediated depletion of p57Kip2 replenishes the proliferation activity of the SCs, thus establishing a role for the Dnmt3a-p57Kip2 axis in the regulation of SC proliferation. Consistent with these findings, Dnmt3a-cKO muscles exhibit fewer Pax7+ SCs, which show increased expression of p57Kip2 protein. Thus, Dnmt3a is found to maintain muscle homeostasis by epigenetically regulating the proliferation of SCs through p57Kip2. How muscle homeostasis is maintained is not completely elucidated yet. Epigenetic disorders such as Beckwith-Wiedemann syndrome, which causes hypergrowth of skeletal muscles and rhabdomyosarcoma, indicate that epigenetic regulations such as DNA methylation, contribute to this homeostasis control. DNA methylation is mediated by DNA methyltransferases, such as Dnmt3a and Dnmt3b, which are de novo DNA methyltransferases. The role of DNA methylation in somatic stem cells is not completely understood, although it has been shown to be indispensable in differentiation of primordial germ cells and embryonic stem cells. In this report, we investigated the role of Dnmt3a in muscle satellite cells by analyzing Dnmt3a-conditional knockout (cKO) mice in which Dnmt3a loci are deleted utilizing Cre-recombinase driven by Pax7 or Pax3 promoters that are specifically activated in the muscle precursor lineage. The loss of Dnmt3a in cKO mice causes decreased muscle mass and significantly impaired muscle regeneration. Moreover, Dnmt3a loss also results in a striking loss of proliferation of SCs, which is caused by mis-expression of a cyclin-dependent kinase inhibitor, p57Kip2. Therefore, our findings suggest that DNA methylation plays an essential role in muscle homeostasis.