Investigating the direct reprogramming of fibroblasts into skeletal muscle progenitors

研究成纤维细胞直接重编程为骨骼肌祖细胞

• 批准号: 10633236
• 负责人: Konrad Hochedlinger
• 金额: $ 43.6万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-15 至 2025-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10633236
• 关键词: Address; Adult; Affect; Binding; Biological Assay; Biological Models; Cell Differentiation process; Cell Line; Cell Maintenance; Cell Separation; Cell Therapy; Cells; ChIP-seq; Characteristics; Chromatin; DNA; Derivation procedure; Disease; Disease model; Dystrophin; Engraftment; Enhancers; Epigenetic Process; Exhibits; Fibroblasts; Future; Gene Expression; Gene Mutation; Gene Targeting; Generations; Genes; Genetic; Genetic Transcription; Germ Layers; Hepatocyte; Human; In Vitro; Individual; Injury; Knowledge; Maintenance; Measures; Memory; Modeling; Molecular; Mouse Strains; Mus; Muscle; Muscle Development; Muscle Fibers; Muscular Dystrophies; MyoD Protein; Myopathy; Neurons; Pattern; Pharmaceutical Preparations; Phenotype; Population; Predisposition; Process; Proliferating; Property; Protocols documentation; Publishing; Reporting; Role; Signal Transduction; Skeletal Muscle; Source; Specific qualifier value; Specificity; Stem cell transplant; System; Testing; Therapeutic; Transgenes; Transplantation; Undifferentiated; cell dedifferentiation; cell type; cofactor; disease phenotype; experimental study; fetal; gene therapy; in vivo; insight; mdx mouse; muscle regeneration; mutant; myogenesis; novel strategies; postmitotic; progenitor; satellite cell; self renewing cell; self-renewal; small molecule; stem; stem cell self renewal; stem cells; stem-like cell; synergism; transcription factor; transcriptome sequencing; transdifferentiation

SUMMARY Transdifferentiation denotes the conversion of one mature cell type into another mature cell upon forced expression of transcription factors or treatment with small molecules. Transdifferentiation systems typically give rise to postmitotic cells, which poses a challenge for mechanistic studies and potential therapeutic applications. To address this shortcoming in the muscle lineage, we recently developed a novel strategy to dedifferentiate fibroblasts directly into “induced myogenic progenitor cells” (iMPCs) by transiently expressing the myogenic transcription factor MyoD in the presence of three small molecules. iMPC cultures are comprised of stem-like cells that give rise to progenitors and mature myofibers exhibiting spontaneous contraction, thus recapitulating key stages of myogenesis in a dish. Moreover, stem-like iMPC subsets can be clonally propagated for at least 20 passages while retaining the ability to produce myotubes, demonstrating long-term self-renewal and differentiation potential in vitro. Accordingly, bulk iMPCs transplanted into mdx dystrophic mice engraft and differentiate into Dystrophin-expressing myotubes in vivo. Thus, our results represent the first successful derivation of stable, expandable and functional muscle stem-like cells directly from fibroblasts and provide the basis for this R01 application using three complementary aims. In SPECIFIC AIM 1, we will compare molecular and functional properties between Pax7+ stem-like cells purified from iMPC cultures and Pax7+ satellite cells purified from skeletal muscle using single-cell expression and chromatin analyses as well as a serial transplantation assay. In addition, we will leverage a tetO-MyoD mouse we recently developed to test whether different cell types are equally amenable to dedifferentiation into iMPCs and whether iMPCs derived from distinct cell types retain a transcriptional memory from their cells of origin. In SPECIFIC AIM 2, we will investigate the molecular mechanisms underlying this dedifferentiation process. First, we will assess whether the establishment and maintenance of iMPCs depend on the same genetic regulators as satellite cells in vivo, with a focus on the transcription factors Pax7, Myf5 and MyoD including MyoD mutants with altered DNA and cofactor binding. We will further explore the specific roles of MyoD and small molecules during iMPC induction by examining enhancer and gene expression dynamics in relation to transdifferentiation (MyoD alone). In SPECIFIC AIM 3, we will test the potential therapeutic utility of iMPCs using mouse and human cells. Briefly, we will assess whether iMPCs from dystrophic mdx mice recapitulate published disease phenotypes in vitro and whether iMPCs are susceptible to gene therapy. Mechanistic insights gained throughout these 3 aims will finally be exploited for efforts to generate human iMPCs. Collectively, our project will provide fundamental insights into the mechanisms by which transcription factors and external signals rewire cell fate using the muscle lineage as a model system and explore how this knowledge could be used in a therapeutic setting. !

概括 转分化是指一种成熟细胞类型在强制作用下转化为另一种成熟细胞。 转录因子的表达或小分子处理。转分化系统通常给出 产生有丝分裂后细胞，这对机制研究和潜在的治疗应用提出了挑战。 为了解决肌肉谱系的这一缺点，我们最近开发了一种新的去分化策略 通过瞬时表达肌源性，将成纤维细胞直接转化为“诱导肌源性祖细胞”（iMPC） 转录因子 MyoD 存在三个小分子。 iMPC 培养物由干状细胞组成 产生祖细胞和成熟肌纤维的细胞表现出自发收缩，从而概括 培养皿中肌生成的关键阶段。此外，茎状 iMPC 子集可以克隆繁殖至少 20次传代，同时保留产生肌管的能力，展示了长期的自我更新和 体外分化潜力。因此，将大量 iMPC 移植到 mdx 营养不良小鼠中并 在体内分化成表达肌营养不良蛋白的肌管。因此，我们的结果代表了第一个成功的 直接从成纤维细胞中衍生出稳定的、可扩展的和功能性的肌肉干细胞，并提供 此 R01 应用程序的基础使用三个互补的目标。在具体目标 1 中，我们将比较分子 从 iMPC 培养物纯化的 Pax7+ 干细胞与 Pax7+ 卫星细胞之间的功能特性 使用单细胞表达和染色质分析以及一系列的方法从骨骼肌中纯化 移植测定。此外，我们将利用我们最近开发的 tetO-MyoD 小鼠来测试是否 不同的细胞类型同样适合去分化为 iMPC，以及 iMPC 是否源自不同的细胞 细胞类型保留了其起源细胞的转录记忆。在具体目标 2 中，我们将调查 这种去分化过程背后的分子机制。首先，我们会评估是否成立 iMPC 的和维持依赖于与体内卫星细胞相同的遗传调节因子，重点是 转录因子 Pax7、Myf5 和 MyoD，包括 DNA 和辅因子结合发生改变的 MyoD 突变体。我们 将通过检查增强子进一步探讨MyoD和小分子在iMPC诱导过程中的具体作用 以及与转分化相关的基因表达动态（仅 MyoD）。在 SPECIFIC AIM 3 中，我们将测试 使用小鼠和人类细胞的 iMPC 的潜在治疗效用。简而言之，我们将评估 iMPC 是否 营养不良的 mdx 小鼠在体外重现已发表的疾病表型以及 iMPC 是否易受影响 到基因治疗。通过这三个目标获得的机制见解最终将被用于努力 生成人类 iMPC。总的来说，我们的项目将为这些机制提供基本见解 通过转录因子和外部信号以肌肉谱系为模型重新连接细胞命运 系统并探索如何将这些知识用于治疗环境。 ！