Analysis of Cell Fate Commitment in Xenopus Embryos.

The fates of individual cleavage-stage blastomeres and of groups of cells at the blastula through gastrula stages of Xenopus embryos have been mapped in great detail. These studies identified the major contributors of the three germ layers as well as a variety of tissues and organs and several specific cell types. One can use these fate maps to test the commitment of single cells or groups of cells to produce their normal repertoire of descendants, to identify the genes that regulate fate commitment, and to modulate the levels of gene expression in specific lineages to determine gene function in a variety of developmental processes. Here we introduce methods that include how to identify specific blastomeres, inject them with lineage tracers, and alter gene expression levels. We also discuss methods for assaying protein and mRNA expression in situ and for providing novel embryonic environments to test fate commitment. These techniques draw upon classical approaches that are quite easy to perform in the versatile Xenopus embryo.