SKELETAL MYOGENESIS - THE PREFERRED PATHWAY OF CHICK-EMBRYO EPIBLAST CELLS IN-VITRO

The epiblast layer of the chick embryo gives rise to all embryonic tis sues. In vitro analyses were carried out to determine whether epiblast cells could form skeletal muscle prior to entry into the primitive st reak. Epiblasts were separated from the mesoderm, hypoblast, and primi tive streak, dissociated to produce a single cell suspension, and plat ed at high density. Myogenesis began on the first day in culture, and by the fifth day most cells had differentiated into skeletal muscle. S ome cells differentiated without replicating. MyoD messenger RNA was p resent in epiblast tissue and translated in practically all cells in c ulture. Cells from regions of the epiblast which do not form muscle la ter in the embryo did so in vitro. Epiblasts cultured for 2 days as an intact epithelium, or in the presence of the mesoderm and hypoblast, did not undergo myogenesis. These findings demonstrate that myogenic p otential is wide-spread within the primitive streak stage epiblast, an d that muscle differentiation, which occurs relatively autonomously in culture, can be prevented by cell and tissue interactions. (C) 1996 A cademic Press, Inc.