Single-cell transplantation determines the time when Xenopus muscle precursor cells acquire a capacity for autonomous differentiation.

We have used a single-cell transplantation technique to find out whether there is a stage in development when a single cell can reach and maintain its differentiated state in the absence of its neighbors. Muscle precursor cells from early, mid-, and late gastrula stages of Xenopus laevis embryos were isolated and transplanted singly into the ventral region of late gastrula hosts. Single cells from late gastrulae differentiated into muscle when surrounded by nonmuscle cells. Similar cells from early or mid-gastrulae did not, unless they were transplanted as a group of adjacent cells taken from the same region of an embryo. These results show that single embryonic cells in a tissue can complete their differentiation without interacting with their normal neighbors and that, in the case of Xenopus muscle precursor cells, they acquire this capacity at the late gastrula stage. Our results also suggest that, in addition to mesoderm induction, further cell interactions during gastrulation are required for Xenopus muscle cell differentiation.