Regulation of Muscle Stem Cell Dynamics and Quiescence by Netrin-1 Cytoskeletal Signaling

Area of Science:

• Cell Biology
• Stem Cell Biology
• Neuroscience

Background:

• Muscle stem cells (MuSCs) are quiescent at homeostasis.
• MuSCs possess complex cellular protrusions with filopodia, suggesting motility.
• These protrusions may function as niche sensors.

Purpose of the Study:

• To develop an ex vivo live imaging assay for MuSC protrusion dynamics.
• To identify regulatory factors involved in MuSC protrusion.

Main Methods:

• Developed an ex vivo live imaging assay for MuSC protrusion dynamics.
• Investigated the role of Netrin-1 signaling pathway components (Dcc, Neogenin, Rac1, Arp2/3) in MuSC protrusions.
• Utilized adult MuSC-specific genetic removal of key regulatory factors.

Main Results:

• Netrin-1 promotes MuSC protrusion outgrowth ex vivo.
• Protrusion outgrowth is dependent on Netrin-1 receptors (Dcc, Neogenin), Rac1, and Arp2/3.
• Genetic removal of these factors impairs homeostatic protrusion length and causes MuSC attrition.

Conclusions:

• Quiescent MuSCs exhibit significant morphological dynamism at homeostasis.
• MuSC protrusions are regulated by axon guidance cue Netrin-1 signaling.
• This protrusion dynamics is essential for maintaining MuSC quiescence and self-renewal.