Epigenetic control of muscle stem cell function by PASK-Wdr5 signaling

项目摘要 肌肉损伤是人类最常见、最常见的损伤类型之一。由于 肌肉干细胞的再生功能，损伤的肌节可以完全恢复其结构和功能 在短短几天内完成功能完整性。除了这种非凡的再生功能外，MUSCs还发挥着 在正常情况下对维持肌肉动态平衡有显著作用。另一方面， 肌肉干细胞功能下降与肌肉萎缩疾病和几种形式的肌肉疾病有关 营养不良。MSC的功能受到它所处的生态位的影响。例如，利基环境会发出 信号调节MuSCs在未损伤状态下静止，或在需要再生时激活。 了解这些信号通路如何控制MuSCs的静止和激活是设计 MSC功能障碍疾病的下一代治疗方法。我们最近描述了一种 MUSCs中新的信号通路通过表观基因激活刺激再生性肌肉生成 Myog启动子的转录。在这个途径中，Per-Arnt-Sim结构域激酶(PASK)被磷酸化 WD40-结构域重复序列5(WDR5)在肌肉发生程序开始时。磷酸化的WDR5刺激 组蛋白H3赖氨酸4(H3K4me3)三甲基化诱导的Myog转录及其募集 MyoG启动子上的MyoD转录因子。我们提出的证据表明PASK的表达和活性 通过信号传递信号，如胰岛素和mTOR复合体1中的营养物质，在再生成肌细胞中诱导 依赖的态度。在功能上，小鼠失去PASK会延缓再生的肌肉发生，并过度表达 会耗尽干细胞。因此，我们假设PASK扮演着平衡自我更新和 再生过程中的分化。在这些数据的基础上，在本提案中，我们将调查 PASK的表达和活性在再生的成肌细胞中受到调节(特异性目标1)。处于激活状态 MUSCs、PASK磷酸化WDR5诱导H3K4me3修饰、MyoD募集和核小体 Myog启动子的重塑机制尚不清楚。在具体目标2中，我们将广泛 研究WDR5的两个相互作用的伙伴，它们可以重塑Myog启动子以使其激活。vt.在.的基础上 在Mygenin诱导下，Pax7的表达下调，并建立了终末分化。自.以来 PASK是Myog表达的上游调控因子，我们有兴趣决定如何失去或获得 在更新和正常老化过程中，PASK会影响自我更新的种群，我们将 研究特定的目标3.最终，这些目标将使我们理解利基信号信号如何控制 自我更新和差异化之间的平衡以及如何利用它来改善 生理状况，如石棺减少症。

Project Summary Muscle trauma is one of the most common and repetitive types of injury in humans. Owing to the regenerative functions of Muscle Stem Cells (MuSCs), the injured myotome can fully regain its structural and functional integrity within just a few days. In addition to this remarkable regenerative function, MuSCs also play a significant role in the maintenance of muscle homeostasis under the normal condition. On the other hand, the decline in MuSCs function is implicated in muscle wasting diseases and several forms of muscular dystrophy. The functions of MuSCs are influenced by the niche it occupies. For example, the niche emits signals to regulate MuSCs quiescence in the uninjured state, or activation when regeneration is required. Understanding how these signaling pathways control quiescence and activation of MuSCs is essential to devise the next generation of therapeutic approaches for diseases of MuSCs dysfunction. We recently described a novel signaling pathway in MuSCs that stimulates regenerative myogenesis by epigenetically activating the transcription of the Myog promoter. In this pathway, Per-Arnt-Sim domain Kinase (PASK) phosphorylates WD40-domain repeat 5 (Wdr5) at the onset of the myogenesis program. Phosphorylated Wdr5 stimulates the Myog transcription by inducing histone H3 trimethylation at lysine 4 (H3K4me3) and the recruitment of the MyoD transcription factor at the Myog promoter. We present evidence that PASK expression and activity is induced in regenerating myoblasts by signaling cues such as insulin and nutrients in mTOR complex 1 dependent manner. Functionally, loss of Pask in mice retards regenerative myogenesis, and over-expression of PASK depletes the stem cells. Thus, we hypothesize that PASK plays a role balancing self-renewal vs differentiation during regeneration. Building upon these data, in this proposal, we will investigate how PASK expression and activity is regulated in the regenerating myoblast (Specific Aim 1). In activated MuSCs, PASK phosphorylated Wdr5 induces H3K4me3 modification, MyoD recruitment and nucleosomal remodeling on the Myog promoter yet the mechanism is not clear. In Specific Aim 2, we will extensively study two interacting partners of Wdr5 which could remodel the Myog promoter for its activation. Upon induction of Myogenin, Pax7 expression is down-regulated and terminal differentiation is established. Since PASK is an upstream regulator of the Myog expression, we are interested determining how loss or gain of PASK affects the self-renewing population during regeneration and normal aging process, which we will study in Specific Aim 3. Ultimately, these aims will allow us to understand how niche signaling cues control the balance between self-renewal and differentiation and how it can be exploited for improvement of physiological conditions such as sarcopenia.