EphA7 promotes contact-dependent myogenesis

EphA7促进接触依赖性肌生成

• 批准号: 10410527
• 负责人: Dawn D Cornelison
• 金额: $ 32.32万
• 依托单位: UNIVERSITY OF MISSOURI-COLUMBIA
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-17 至 2025-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10410527
• 关键词: Address; Adhesions; Adult; Animals; Binding; Biology; Birth; Cell Culture Techniques; Cell Differentiation process; Cell membrane; Cell physiology; Cell surface; Cells; Cephalic; Communities; Data; Development; Developmental Process; Differentiation Antigens; Embryo; Eph Family Receptors; Ephrin-A5; Ephrins; Epigenetic Process; Exhibits; Exposure to; Extracellular Domain; Fiber; Genetic Transcription; Giant Cells; Hindlimb; Human; Hypertrophy; In Vitro; Individual; Injury; Lead; Life; Ligands; Link; Mediating; Mediator of activation protein; Membrane; Modeling; Molecular; Mus; Muscle; Muscle Cells; Muscle Development; Muscle Fibers; Muscle satellite cell; Myoblasts; Myogenin; Natural regeneration; Neural Tube Closure; Phenotype; Population; Process; Proliferating; Proteins; Receptor Protein-Tyrosine Kinases; Regenerative Medicine; Resistance; Role; Serum; Signal Transduction; Signal Transduction Pathway; Signaling Molecule; Skeletal Muscle; Surface; Testing; Tissue Differentiation; Tissue Engineering; Tissues; Vertebrates; Work; adverse outcome; base; density; experimental study; fetal; in vivo; in vivo regeneration; innovation; insight; member; muscle form; muscle regeneration; muscle strength; myogenesis; postnatal; precursor cell; prevent; protein protein interaction; receptor; repaired; retinal axon; satellite cell; stem cell expansion; transcription factor; translational applications

SUMMARY The conversion of proliferating skeletal muscle precursors (myoblasts) to terminally-differentiated myocytes is a critical step in skeletal muscle development and repair; control of this process is therefore of fundamental importance in both muscle development and muscle regeneration after injury. The tendency for myogenic cells cultured densely to differentiate and, conversely, the resistance to differentiation of cells at low density has been called the 'Community Effect'; understanding this phenomenon represents a basic question in muscle biology. Based on our initial observation that EphA7, a juxtacrine signaling molecule, is expressed on myocytes during embryonic and fetal myogenesis and on nascent myofibers during muscle regeneration in vivo we examined the muscle phenotype of EphA7-/- mice. We found that their hindlimb muscles possess fewer myofibers at birth, and those myofibers are reduced in size and have fewer myonuclei and reduced overall numbers of precursor cells throughout postnatal life. Adult EphA7-/- mice have reduced numbers of satellite cells and exhibit delayed and protracted muscle regeneration, and satellite cell-derived myogenic cells from EphA7-/- mice are delayed in their expression of differentiation markers in vitro. Exposure to exogenous EphA7 extracellular domain will rescue the null phenotype, and will also accelerate commitment to differentiation in WT cells, which led us to propose a model in which EphA7 expression on differentiated myocytes promotes commitment of adjacent myoblasts to terminal differentiation via reverse signaling. The experiments we propose in Aims 1 and 2 will address the role of EphA7 in myogenic commitment in both the myocyte ("How does commitment to differentiation lead to expression of EphA7?") and the myoblast ("How does receiving an EphA7 signal lead to commitment to differentiation?"). Once they have differentiated, myocytes must fuse with each other or with a growing myotube in order to generate a functional muscle cell (the contractile myocyte fiber), thus this also represents a critical process in both development and regeneration. However, the molecular requirements for fusion in mammalian muscle cells have been elusive. Our data suggest EphA7 also promotes myogenic fusion, possibly via different molecular mechanisms/interactions from its role in promoting myogenic differentiation. The experiments we propose in Aim 3 will test the ability of EphA7 to promote fusion in myogenic and nonmyogenic cells, determine whether it associates with the cell-surface fusogen myomaker, and identify other protein-protein interactions it is participating in at the interface of myocytes and growing myotubes in cis (on the same cell membrane) or in trans (on opposing cell membranes). Collectively, these studies will address the molecular mechanisms regulating two fundamental cellular processes during myogenic differentiation; they also have the potential to provide insight into potential innovations in muscle stem cell expansion in vitro and thus applications in tissue engineering and regenerative medicine.

总结 增殖的骨骼肌前体细胞（成肌细胞）向终末分化的肌细胞的转化 是骨骼肌发育和修复的关键步骤;因此， 在肌肉发育和损伤后肌肉再生中具有根本重要性。的趋势 密集培养以分化的肌源性细胞，相反， 低密度被称为“社区的平衡”;理解这种现象代表了一个基本的 肌肉生物学的问题。基于我们最初的观察，EphA 7，一种阿曲他克林信号分子， 表达于胚胎和胎儿肌形成过程中的肌细胞和肌肉形成过程中的新生肌纤维 在体内再生中，我们检查了EphA 7-/-小鼠的肌肉表型。我们发现它们的后肢 肌肉在出生时拥有较少的肌纤维，这些肌纤维的大小减少， 在整个出生后的生活中，肌核和减少的前体细胞总数。成年EphA 7-/-小鼠 卫星细胞数量减少，肌肉再生延迟和延长， 来自EphA 7-/-小鼠的卫星细胞衍生的肌原性细胞在其分化表达中延迟 体外标记物。暴露于外源性EphA 7胞外结构域将拯救无效表型，并且将 也加速了WT细胞的分化，这使我们提出了一个模型，其中EphA 7 在分化的肌细胞上的表达促进邻近的成肌细胞向终末的定向 通过反向信号进行分化。我们在目标1和目标2中提议的实验将探讨 EphA 7在肌细胞中的肌原性定型（“分化定型如何导致 EphA 7的表达？）和成肌细胞（“接受EphA 7信号如何导致承诺， 分化？").一旦它们分化，肌细胞必须彼此融合或与生长的细胞融合。 肌管以产生功能性肌细胞（收缩性肌细胞纤维），因此这也 代表了发展和再生的关键过程。然而，分子要求 在哺乳动物肌肉细胞中进行融合的方法一直是难以捉摸的。我们的数据表明EphA 7也促进肌源性 融合，可能通过不同的分子机制/相互作用，从它的作用，促进肌源性 分化我们在目标3中提出的实验将测试EphA 7促进融合的能力。 肌原性和非肌原性细胞，确定其是否与细胞表面融合原肌原性因子相关， 并确定它在肌细胞界面参与的其他蛋白质-蛋白质相互作用， 顺式（在同一细胞膜上）或反式（在相对的细胞膜上）的肌管。总的来说，这些 研究将解决调节两个基本细胞过程的分子机制， 肌源性分化;他们也有潜力提供洞察肌肉的潜在创新 干细胞体外扩增以及因此在组织工程和再生医学中的应用。