(A) Wnt1 expression in the caudal rhombic lip in normal animal at 11.5 dpc. The caudal rhombic lip has a dorsal-ventral graded expression of Wnt1. The mossy fiber precerebellar neurons originate from the dorsal domain of the caudal rhombic lip specified by high expression of Wnt1 (arrowhead). Climbing fiber neurons are derived from a more ventral domain of the caudal rhombic lip which expresses a low level of Wnt1 (arrow). (B) The domain of Wnt1 expression was reduced in Bmpr double knockout animals. (C, D) Gdf7, which is expressed in the lateral roof plate, is present in both the normal animals and Bmpr double knockout mutants at 11.5 dpc. The non-Gdf7 expressing medial roof plate was missing in Bmpr mutant (compare arrowhead in C and D). (E, F) Lmx1a, which is expressed in both the lateral and medial roof plate, was significantly reduced in Bmpr mutant at 11.5 dpc. Scale bar: A (for A-F), 50 μm.