RESUMEN
Adult muscle stem cells and their committed myogenic precursors, commonly referred to as the satellite cell population, are involved in both muscle growth after birth and regeneration after damage. It has been previously proposed that, under these circumstances, satellite cells first become activated, divide and differentiate, and only later fuse to the existing myofiber through M-cadherin-mediated intercellular interactions. Our data show that satellite cells fuse with the myofiber concomitantly to cell division, and only when the nuclei of the daughter cells are inside the myofiber, do they complete the process of differentiation. Here we demonstrate that M-cadherin plays an important role in cell-to-cell recognition and fusion, and is crucial for cell division activation. Treatment of satellite cells with M-cadherin in vitro stimulates cell division, whereas addition of anti-M-cadherin antibodies reduces the cell division rate. Our results suggest an alternative model for the contribution of satellite cells to muscle development, which might be useful in understanding muscle regeneration, as well as muscle-related dystrophies.