FIG. 1.

Diagram to illustrate the origin and fate of TSC in the mouse. Stem cell precursors in polar TE are hypothesized to give rise to a population of TSC. TSC are located adjacent to the developing epiblast, which arises from the ICM (see Fig. 2). The TSC self-renew but also generate faster-dividing, multipotent progenitors that provide the precursors of the differentiated cell types of the placenta. The information shown is speculative, and the differentiated tissue lineages are minimized for simplicity.