(A) Developmental expression of Runx1, N-Tub, and Ngnr1 at the neural plate border in stage-matched embryos. The arrows indicate the position of the row of RB sensory neurons. Dorsal views, anterior to top. (B–C) In situ hybridization on adjacent transverse sections of stage 15 and stage 19 embryos, dorsal to top. (B) At stage 15 Runx1 is co-expressed with N-Tub and Ngnr1, as indicated by the red overlay in the lower panels. (C) At stage 19 while Runx1 and N-Tub are still co-expressed, Ngnr1 expression is lost in the RB neurons population, as indicated by the red overlay in the lower panels. The dotted lines demarcate the position of the spinal cord.