Role of STAT3 in muscle stem cell activation

描述（由申请人提供）：成体肌肉干细胞（MuSC），也称为卫星细胞，是骨骼肌再生的主要来源。MuSC在健康成人组织中处于静止状态，在受到应激或损伤时被激活增殖，产生大量祖细胞修复受损组织。虽然静止和激活之间的平衡是MuSC功能的一个关键开关，但调节这一转变的分子机制仍在很大程度上未知。对调节MuSC功能的网络的更好理解将促进它们在再生医学中的应用，以开发肌肉萎缩疾病的治疗方法。我们的初步研究结果表明，STAT3调节MuSC增殖，并在bHLH肌生成调节因子MyoD的转录激活中起直接作用，这是MuSC退出静止状态的关键事件。在细胞因子的刺激下，STAT3被JAK激酶磷酸化，易位到细胞核并结合DNA激活靶基因的转录。本研究的重点是研究STAT3在MuSC自我更新、激活和肌生成中的作用，并确定其相关的下游靶点。我们的研究将利用以下工具：(1)结合时间延迟显微镜进行功能丧失研究，以监测原位MuSC激活；(2)染色质免疫沉淀（ChIP）、ChIPseq和微阵列基因表达谱分析，以鉴定MuSC中新的STAT3下游靶点；(3)MuSC中STAT3的条件基因消融，以评估其在完整动物体内MuSC自我更新和维持中的作用；(4)从患者分离的人类MuSC。以确定STAT3在MuSC功能中的关键作用是否在两个物种之间保守。总之，这些研究将确定STAT3和MyoD之间的直接功能相互作用，并进一步扩展我们对STAT3在MuSC激活中的调控网络的了解。最后，这些发现将有助于制定旨在促进肌肉干细胞介导的组织再生的策略，以改善肌肉萎缩性疾病。

DESCRIPTION (provided by applicant): Adult muscle stem cells (MuSC), also known as satellite cells, are the main source skeletal muscle regeneration. MuSC exist in healthy adult tissues in a quiescent state, and upon stress or injury they are activated to proliferate and generate large numbers of progenitors to repair the damaged tissue. Although the balance between quiescence and activation is a critical switch in MuSC function, the molecular mechanisms regulating this transition are still largely unknown. An improved understanding of the networks regulating MuSC function would facilitate their use in regenerative medicine for the development of therapeutic approaches for muscle wasting diseases. Our preliminary findings indicate that STAT3 regulates MuSC proliferation as well as plays a direct role in the transcriptional activation of the bHLH myogenic regulatory factor MyoD, a key event as MuSC exit the quiescent state. Upon cytokine stimulation, STAT3 is phosphorylated by JAK kinases, translocates to the nucleus and binds DNA to activate the transcription of target genes. The focus of this proposal is to investigate the role of the STAT3 in MuSC self-renewal, activation and myogenic commitment and to identify its relevant downstream targets. Our research will take advantage of the following tools: (1) Loss of function studies in conjunction with time-lapse microscopy, to monitor MuSC activation in situ, (2) Chromatin ImmunoPrecipitation (ChIP), ChIPseq and microarray gene expression profiling, in order to identify novel STAT3 downstream targets in MuSC, (3) Conditional genetic ablation of STAT3 in MuSC, in order to evaluate its role in MuSC self-renewal and maintenance in vivo in the intact animal, and (4) Human MuSC isolated from patients, to determine whether the critical role of STAT3 in MuSC function is conserved in between the two species. Together, these studies would identify a direct functional interaction between STAT3 and MyoD, and further extend our knowledge of the STAT3 regulatory network in MuSC activation. Finally, these findings would aid in the development of strategies aimed at promoting muscle stem cell-mediated tissue regeneration to ameliorate muscle-wasting diseases.