On the migration of myogenic stem cells into the prospective wing region of chick embryos. A scanning and transmission electron microscope study.

In chick embryos undifferentiated myogenic stem cells migrate from the ventrolateral somite respectively dermatome edge into the prospective wing region after the second day of incubation. At first, single cells that are elongated in mediolateral direction, later also small groups of cells, are found in the space between somites and somatopleura at the wing bud level. The leading ends of the migrating cells are formed like finger-shaped lobopodia as well as flattened lamellipodia from which thin filopodia arise. The main structural features of the cell processes are microtubules and microfilaments predominantly oriented parallel to the long axis of the cells. The filopodia are found to be in close connection with the surrounding network of collagen fibrils. Since the main strands of the fibrils show a mediolateral orientation, it may be assumed that the direction of cell migration depends on the arrangement of the collagen fibrils.