Colonization of the Satellite Cell Niche by Skeletal Muscle Progenitor Cells Depends on Notch Signals

Skeletal muscle growth and regeneration rely on myogenic progenitor and satellite cells, the stem cells of postnatal muscle. Elimination of Notch signals during mouse development results in premature differentiation of myogenic progenitors and formation of very small muscle groups. Here we show that this drastic effect is rescued by mutation of the muscle differentiation factor MyoD. However, rescued myogenic progenitors do not assume a satellite cell position and contribute poorly to myofiber growth. The disrupted homing is due to a deficit in basal lamina assembly around emerging satellite cells and to their impaired adhesion to myofibers. On a molecular level, emerging satellite cells deregulate the expression of basal lamina components and adhesion molecules like integrin α7, collagen XVIIIα1, Megf10, and Mcam. We conclude that Notch signals control homing of satellite cells, stimulating them to contribute to their own microenvironment and to adhere to myofibers. [Display omitted] ► Premature muscle differentiation after Notch ablation is rescued by a MyoD mutation ► Rescued myogenic progenitor cells do not assume a satellite cell position ► Instead, such cells locate interstitially and contribute poorly to myofiber growth ► Notch stimulates satellite cells to produce basal lamina and to adhere to myofibers Elimination of Notch signaling during mouse development results in premature differentiation of myogenic progenitors and formation of tiny muscle groups. Bröhl et al. find that mutating MyoD rescues this defect; however, rescued progenitors are defective in extracellular matrix production and myofiber adhesion. These results link satellite cell maintenance and homing.