Fig. 4. p27^Xic1 acts at an early stage of neurogenesis. Embryos co-injected with 50 pg X-NGNR-1 and 20 ng Con Mo (A) or p27^Xic1 Mo (B) were analysed for Nßtub expression (purple) by whole-mount in situ hybridisation, injected side to the left (ß-gal, light blue). Co-injection of X-NGNR-1 with Con Mo produces extensive ectopic neurones (A), while p27^Xic1 Mo prevents both endogenous and ectopic primary neurogenesis (B). (C) Co-injection of p21^Cip1 with X-NGNR-1 rescues downregulation of Nßtub expression by p27^Xic1 Mo. Embryos were co-injected with 400 pg NeuroD and 20 ng Con Mo (D) or p27^Xic1 Mo (E). NeuroD is able to induce extensive ectopic Nßtub even in the absence of p27^Xic1 protein (E).