Deciphering the molecular mechanisms of skeletal muscle fiber fusion

Objective

Skeletal muscle fibers are highly organized multinucleated cells that grow and regenerate by fusing with myocytes derived from their resident stem cells. The fusion between myocytes and mature muscle fibers, which underpins the remarkable adaptability of muscles, is molecularly distinct from the fusion events that occur during development. This secondary fusion process, also known as myonuclear accretion, integrates mononucleated myocytes into immature myotubes or mature fibers, supporting muscle growth, repair, and regeneration throughout life. Despite its critical physiological importance, the mechanisms governing secondary fusion and the active role of myofibers in this process remain poorly understood. Leveraging the development and application of high-content screening, advanced biochemistry, genetics, cell biology, transcriptomics, and cutting-edge imaging techniques, including 3D correlative light and electron microscopy (CLEM), we aim to provide groundbreaking insights into the molecular and cellular processes of secondary fusion. To achieve this, we will address three independent but interconnected aims: Aim 1: Screen for regulators of secondary fusion and determine their effects using high-content imaging together with exploratory molecular studies. Aim 2: Elucidate the molecular mechanisms and cellular dynamics underpinning fusion hotspots. Aim 3: Establish the physiological relevance of myonuclear accretion in vivo by visualizing fusion hotspots and evaluating the impact of enhanced myoblast transplantation on muscle regeneration and function. This synergistic approach will transform our understanding of muscle physiology, bridging the molecular mechanisms with their functional outcomes. The findings promise to uncover new principles of cell fusion, organelle dynamics, and tissue adaptability, offering profound implications for muscle biology and novel therapeutic strategies for muscle-wasting diseases.