Notch signaling/MyoD double deficient embryonic muscle progenitors

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 deregulate the expression of basal lamina components and adhesion molecules like integrin a7, collagen XVIIIa1, 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. Gene expression analysis using total RNA from FACS-isolated Vcam-1+/CD31-/CD45-/Sca1- embryonic muscle progenitor cells from E17.5 back muscle tissue of MyoD-/-, Pax3cre/+;Rbpjflox/flox;MyoD-/- and Pax3cre/+;DnMamlflox/flox;MyoD-/- mice.