In vitro differentiation assays demonstrated that low-pH-induced Oct4-GFP+ cells gave rise to three-germ-layer derivatives (Fig. 2d) as well as visceral endoderm-like epithelium (Extended Data Fig. 3d). When grafted into mice, low-pH-induced Oct4-GFP+ cell clusters formed teratomas (40%, n = 20) (Fig. 2e and Extended Data Fig. 4a–c) but no teratocarcinomas that persistently contained Oct4-GFP+ cells (n = 50). Because some cellular variation was observed in the signal levels of Oct4-GFP within the clusters, we sorted GFP-strong cells (a major population) and GFP-dim cells (a minor population) by FACS on day 7 and separately injected them into mice. In this case, only GFP-strong cells formed teratomas (Extended Data Fig. 4d).
exist, and in whichtissues do they exist?
How do adult stem cells evolve during development and how are they maintained in
the adult? Are they "leftover" embrj'^onic stem cells, or do they arise in some other
way?
Through years of experimentation, scientists have established some basic protocols
or "recipes" for the directed differentiation of embryonic stem cells into some specific
cell types.
