N-cadherin is involved in myoblast migration and muscle differentiation in the avian limb bud

Limb muscle formation involves invasion of the limb bud mesoderm by myogenic precursor cells from the dermomyotomes at limb bud level. Directed cell migration, homing, and differentiation of myogenic cells are controlled by the stationary cells of the limb bud mesoderm. At the level of the extracellular matrix, the molecular basis of migration control has been suggested to be exerted by the distribution of hyaluronan. Here, we demonstrate that N-cadherin-mediated interactions play a role at cell-membrane level in myoblast distribution and differentiation. N-cadherin is strongly expressed by myogenic cells in the chick limb bud and more moderately expressed by stationary mesodermal cells in the myogenic zones and progress zone. After in vivo injection of antibodies and Fab-fragments against the homophilic binding site of N-cadherin into the wing bud mesoderm, aggregates of myoblasts are found predominantly in the dorsal myogenic zone 36 hr after injection apparently due to immobilization. In the same position, areas of myf-5-positive cells are also observed. In injected limb buds, Pax-3-positive cells are less evenly distributed than in uninjected limbs. They are found to spread up to the epidermis and also form loosely arranged aggregates. After prolonged reincubation periods; injected limbs show ectopic myoblasts that are rich in desmin and areas of strongly desmin-expressing myoblasts within muscle blastemas. These effects were not observed after application of antibodies against other parts of the N-cadherin molecule. We conclude that N-cadherin is involved in myoblast migration in the limb buds via homophilic interactions and that it plays a role in signal transduction during myogenesis.