Temporal separation of the migration of distinct myogenic precursor populations into the developing chick wing bud.

The developing chick limb bud contains several stage-specific populations of muscle colony-forming (MCF) cells. The cell lineage relationships of these populations are not completely understood, but previous studies have suggested that there may be at least two myogenic precursor populations present in the limb bud. To investigate the heterogeneity of the precursor population, the migration of myogenic precursor cells into the wing anlagen was stopped at various times by grafting stage 15-18 wing buds to the flank or chorioallantoic membrane regions of host embryos. The grafted wings were subsequently assayed for the various MCF cell populations. The data provide further support for the existence of two distinct myogenic precursor populations that migrate into the wing anlagen at different times; precursors to early MCF cells are present by stage 15, whereas precursors to late MCF cells are not present until the end of stage 16. The fact that wing buds which are grafted to a foreign location at stage 15 exhibit exclusive development of early MCF cells suggests that late MCF cells are not direct cell lineage descendants of either the early-type precursors or early MCF cells.