Fig. 5. Expression patterns of Notch signaling cascade components and neuronal markers calbindin D 28k and ß-tubulinIII (TuJ1) at E12.5. In situ RNA hybridization on cross-sections through the neural tube, dorsal to the left and ventral to the right, of E12.5 mutant (/) (A,C,E,G) and control embryos (lox/lox) (B,D,F,H) show that the extended expression of Dll1 (A,B) observed in E10 mutants compared with controls was no longer seen at E12.5 and the induction of Dll3 (arrow, C,D) and Mash1 (E,F) was detectable but less pronounced than at E10. In situ RNA hybridization did not reveal precocious expression of calbindin D 28k (G,H) in the mutant compared with control animals. Expression of the pan-neuronal marker ß-tubulin (TuJ1) (I,J) revealed differentiated cells in the lateral aspects of the cerebellum (arrows) but no precocious neurogenesis in the mutants. Scale bar: 100 µm.