MYOGENIC CELL-MIGRATION FROM SOMITES IS INDUCED BY TISSUE CONTACT WITH MEDIAL REGION OF THE PRESUMPTIVE LIMB MESODERM IN CHICK-EMBRYOS

It is known that myogenic cells in limb buds are derived from somites. In order to examine the potential of the limb primordium (presumptive limb somatopleure) to induce myogenic cell migration, we transplanted chick presumptive limb somatopleure to the flank region of an embryo, a region that does not normally contribute myogenic cells to the limb . Semitic cell migration was examined using a vital labeling technique . When the presumptive limb somatopleure was transplanted and was in c ontact with the host flank somite, semitic-cell migration toward the g raft was observed. The labeled semitic cells within the graft were ide ntified as myogenic cells in two ways: first, we found that N-cadherin -expressing cells appeared in the graft. Second, after 3 further days of incubation, the semitic cells formed dorsal and ventral masses and expressed sarcomeric myosin heavy chain within the graft. Cell migrati on occurred only when the somite was in contact with the medial region of the presumptive limb somatopleure. When the somite was not in cont act with the limb somatopleure, or when the somite was in contact with the lateral region of the limb somatopleure, migration did not occur. These observations indicate that the potential to induce myogenic cel l migration is restricted to the medial region of the presumptive limb somatopleure and that tissue contact is required.