Migration of Myogenic Cells in the Developing Limb

Myogenic cells migrate into the limb from the somitic mesoderm, taking up positions in the dorsal and ventral compartments before differentiating into the limb musculature. This process is influenced by the tissues of the limb in a number of ways. Cells of the lateral part of the somitic dermomyotome are induced to express a migratory myogenic phenotype by a diffusible signal originating in the limb bud mesoderm. The limb and body wall musculature are entirely derived from cells of this migratory myogenic lineage. Components of the extracellular matrix of the limb mesoderm, such as fibronectin, facilitate myogenic cell migration by providing sites for adhesion and directed migration. Differences in the composition of the matrix along the proximo-distal axis make the distal mesoderm more attractive for migrating myogenic cells. Anterior-posterior movement of myogenic cells within the limb bud is highly restricted, resulting in a regionalised contribution of cells to the limb musculature based on somitic origin. Lastly, there is a process that excludes myogenic cells from the most distal region of the limb bud mesoderm; a similar process is involved in the aggregation of myogenic cells into the dorsal and ventral premuscle masses. These findings illustrate the high degree of control over myogenic cell migration mediated by both diffusible factors and the extracellular matrix in the developing limb mesenchyme.