The effect of skp2 over-expression on neural differentiation is partially rescued by extra Xic1. (a-c) Embryos were injected with wild-type skp2 (a) or wild-type Xic1 (b) mRNA alone, or together (c), 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. (d) Percentages of embryos with mild increase, no change, or moderate or substantial reduction of nßt-positive cells on the injected side relative to the uninjected side (see Additional file 1 for photographs of representative embryos).