skp2 inhibits primary neurogenesis between XNgnr1 and NeuroD. (a-f) Embryos were injected with XNgnr1 (a) or NeuroD (d) mRNA alone, or together with Wt skp2 (b,e) or FBox skp2 (c,f) mRNA, in one blastomere at the two cell stage. ßgal mRNA was co-injected as a lineage tracer. Embryos were analyzed for expression of nßt mRNA at stage 15. Dorsal views with injected side to the right.