Fig. 10. Summary of the phenotype of dorsal neural tube development in Bmpr1a;Bmpr1b double knockout animals. (A) On the left, the normal distribution of dorsal interneurons, DI1-DI6, are schematically illustrated. Ventral subtypes, V0-V3 and MN are shown in grey. The neuron populations are characterized by expression of LIM-homeodomain factors, shown on the right. The ventricular zone of the developing spinal cord is subdivided by the expression domains of the bHLH factors, as shown. (B) In the Bmpr double knockout animals, the DI1 population is absent, as shown by the loss of Lhx2 and Lhx9. Furthermore, Math1 expression in the ventricular zone is also lost. The other bHLH domains are intact but shifted dorsally. Only a small number of DI2 cells remain with decreased expression of Foxd3 and Lim1/2. The DI3 and DI4 populations are shifted dorsally as well.