Figure 3.

Neurod1-Cre induced overexpression of constitutively active smo results in retention of a variable sized external granule layer (EGL) in each lobe (small * in B) and medulloblastoma (MB) formation in the posterior lobe (large * in B, lobe X) of the cerebellum. Higher magnification reveals that instead of molecular layers separated only by a thin layer of meninges (Pia in D,H) the EGL of adjacent folia merge (E). In lobes IX and X small MBs form that show abundant proliferation as demonstrated by numerous cell divisions (I). Overexpression of Neurod1 suppresses the formation of extra EGL and MB formation caused by smo overexpression, resulting in near normal EGL in anterior lobes (F, G, K, arrows in C) and reduced EGL in posterior lobes (arrow heads in C). Starting at lobe VII (C) there was a variable formation of MB (C, J) Scale bars= 1mm in A,B,C and 100 μm all other images.