Figure 2.

Regulatory switch between quiescent and activated states of satellite cells. Notch and Wnt signaling antagonize each other to define the state of satellite cells. Upon binding of DSL ligands (Delta) to Notch receptor, released Notch intracellular domain (NICD) translocates to the nucleus. After associating with RBP-Jκ, the complex activates the transcription of target genes, such as Hes, Hey, and Pax7 to maintain satellite cells in quiescent state (left). When the “molecular switch” turns from the quiescent state to the activation state by Wnt proteins (right), the Wnt signal transduction activates β-catenin/TCF/LEF transcriptional complexes. The transcription complex triggers the expression of target MyoD gene and positively regulates myogenic differentiation.