Analysis of frequency of intermingling between labeled clones in Xenopus embryos.

These experiments were designed to provide data that would test alternative hypotheses of the basis of clonal intermingling during early development of Xenopus. Clones were initiated by injection of different fluorescent cell lineage tracers into two blastomeres in the same 512-cell embryo. In order to find out how frequently clonal intermingling or clonal separation developed between the progeny of two ancestral cells at different distances apart, the pair of injected cells was either adjacent, separated by one uninjected cell, or separated by two uninjected cells, chosen at random in the animal dorsal region of the embryo. The final positions of the labeled clones were analyzed at tailbud stages. The results closely match the probability of interclonal mingling predicted by a compartment model, in which two clones intermingle or remain separate as a function of the probability of a clonal restriction boundary developing between them, rather than as a continuous function of the distance between the two cells at the time of labeling.