The community effect in Xenopus myogenesis is promoted by dorsalizing factors.

The community effect describes a process required for Xenopus muscle progenitor cells to progress to the expression of myogenic genes. Past work has suggested that this effect is dependent on secreted factors released by dorsolateral or dorsal lip cells. We show here that known dorsalizing molecules as well as other natural dorsal lip factors contribute to, but do not wholly account for, the community effect. We conclude that, in addition to dorsalizing molecules, the community effect requires factors or conditions peculiar to the dorsolateral mesoderm, a region of the embryo that contains muscle progenitor cells.