Fig. 6. Response of whole ectodermal explants to Activin. (A) Animal pole explants were dissected and incubated in the presence or absence of Activin protein for the indicated times. Explants were dissociated in CMFM at hourly intervals (0 hour time point is before addition of Activin) and single cells were picked for RT-PCR. Intact caps remaining at 4 hours were assayed by real-time RT-PCR. (B) Real-time RT-PCR of intact caps shows high levels of expression of XK70A and Xbra, lower levels of Mix.1, and almost no induction of Sox17 after 4 hours. (C) The gene expression profile of individual cells at different times is shown in the presence and absence of Activin.