M-cadherin localization in developing adult and regenerating mouse skeletal muscle: possible involvement in secondary myogenesis.

In this work, we investigated the distribution of the Ca(2+)-dependent cell adhesion molecule, M-cadherin, in mouse limb muscle during normal development and regeneration. Using two unrelated anti-M-cadherin peptide antibodies, we found scarce M-cadherin immunostaining during primary myogenesis (E12-E14) with no accumulation at areas of cell-cell contact. In contrast, the staining sharply increased in intensity at E16, remained high during secondary myogenesis (E16-P0) but disappeared soon after birth. During secondary myogenesis, M-cadherin was specifically accumulated at the characteristic sites of insertion of secondary myotubes in neighbouring primary myotubes. M-cadherin was also accumulated at the areas of contact between fusing secondary myoblasts and myotubes in vitro. In the adult normal and regenerating muscle, we did not detect M-cadherin accumulations at the surface of myofibres. All together, these observations suggest that M-cadherin is specifically involved in secondary myogenesis.