CD47 Promotes, While Exposure to Apoptotic Cells Destroys the Fusion Program of Differentiating Myoblasts

Area of Science:

• Muscle biology
• Cellular mechanisms
• Immunology

Background:

• Cell fusion and phagocytosis share molecular pathways in myoblasts.
• Viable cells express "don't eat-me" signals to avoid phagocytosis.
• Understanding how myoblasts choose between fusion and phagocytosis is crucial for muscle regeneration.

Purpose of the Study:

• To investigate the role of "don't eat-me" signals in myoblast fusion versus phagocytosis.
• To determine how myoblasts decide between fusion and phagocytosis pathways.
• To elucidate the function of CD47 signaling in myoblast differentiation and fusion.

Main Methods:

• RNA sequencing analysis of C2C12 mouse myoblast cells.
• In vivo studies using cardiotoxin-induced injury in mouse skeletal muscle.
• Functional assays using anti-CD47 antibody and thrombospondin-1 blocking.

Main Results:

• Differentiation upregulated "don't eat-me" genes, including Sirpα (receptor for CD47), in myoblasts.
• Blocking CD47 signaling significantly reduced myoblast fusion but not survival or differentiation.
• CD47 signaling promotes myoblast fusion and prevents accidental phagocytosis of live cells.

Conclusions:

• Differentiating myoblasts upregulate CD47 to balance phagocytosis and promote fusion.
• CD47 signaling is a key decision-making factor between myoblast fusion and phagocytosis.
• This pathway is essential for effective muscle regeneration by ensuring proper myoblast fusion.