Figure 4.

Lateral views of two embryos (A and B) at approximately 24 hpf stained to reveal spt transcription. Dorsal is up and rostral is to the left. DIC microscopy was used to reveal somite boundaries. Consequently, spt-expressing cells in the developing CNS are not seen clearly because they lie in a different focal plane. However, the most rostral cell in each embryo is indicated by a white arrrowhead. The most rostral visible discernible somite is indicated by a white arrow. In both cases there are 6 somites rostral to the most rostral spt-expressing neuron. Scale bars equal 100 μm.