EphA7 promotes contact-dependent myogenesis

EphA7促进接触依赖性肌生成

基本信息

批准号：
10219157
负责人：
Dawn D Cornelison
金额：
$ 31.68万
依托单位：
UNIVERSITY OF MISSOURI-COLUMBIA
依托单位国家：
美国
项目类别：
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/10219157
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 Cultured Cells 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

项目摘要

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.

概括增殖的骨骼肌前体细胞（成肌细胞）转化为终末分化的肌细胞是骨骼肌发育和修复的关键步骤；因此，对该过程的控制是对于肌肉发育和受伤后的肌肉再生至关重要。趋势为密集培养的生肌细胞可分化，相反，细胞对分化的抵抗力低密度被称为“社区效应”；理解这一现象代表了一个基本的肌肉生物学问题。根据我们的初步观察，EphA7（一种近分泌信号分子）是在胚胎和胎儿肌发生过程中在肌细胞上表达，在肌肉过程中在新生肌纤维上表达我们检查了 EphA7-/- 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，并且这些肌纤维的尺寸减小并且具有较少的肌纤维。肌核和整个出生后生命中前体细胞总数的减少。成年 EphA7-/- 小鼠卫星细胞数量减少，肌肉再生延迟且延长，并且来自 EphA7-/- 小鼠的卫星细胞衍生的肌原细胞的分化表达延迟体外标记。暴露于外源 EphA7 胞外结构域将挽救无效表型，并且将还加速了 WT 细胞分化的过程，这促使我们提出了一个模型，其中 EphA7 分化的肌细胞上的表达促进相邻成肌细胞向终末期的定向通过反向信号进行分化。我们在目标 1 和 2 中提出的实验将解决 EphA7 在两个肌细胞的肌原性承诺中（“分化承诺如何导致 EphA7 的表达？”）和成肌细胞（“接收 EphA7 信号如何导致承诺分化？”）。一旦分化，肌细胞必须彼此融合或与正在生长的细胞融合。肌管以产生功能性肌细胞（收缩肌细胞纤维），因此这也代表发育和再生的关键过程。然而，分子要求哺乳动物肌肉细胞中的融合一直难以实现。我们的数据表明 EphA7 还促进生肌融合，可能通过不同的分子机制/相互作用来促进生肌差异化。我们在目标 3 中提出的实验将测试 EphA7 促进融合的能力肌源性和非肌源性细胞，确定它是否与细胞表面融合剂肌细胞相关，并识别它在肌细胞界面参与和生长的其他蛋白质-蛋白质相互作用肌管呈顺式（在同一细胞膜上）或反式（在相对的细胞膜上）。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原性分化；他们还有潜力深入了解肌肉的潜在创新干细胞体外扩增及其在组织工程和再生医学中的应用。