Figure 2.

Temporal expression profiles of selected ectodermal genes establishing oral-aboral polarity at the blastula stage. A) Time courses for nodal, not, vegf3, gsc, and foxg. These genes are activated sequentially between 8 hr and 18 hr. B) Time courses for ets4 and sip1. Zygotic activation of ets4 and sip1 is concurrent with nodal transcription; ets4 is also transcribed maternally. After 11–12 h, transcript levels of sip1 and ets4 undergo a sharp decline.