Figure 3.

Atoh1 deletion prevents tumor formation in a mouse model of Shh-induced medulloblastoma. Pictures of A) P14 cerebella of a control animal that did not receive tamoxifen, and thus doesn't express the activated form of Smoothened; of B) an Atoh1^wt and of C) an Atoh1^▵ animal injected with tamoxifen to activate the expression of the constitutively active Smoothened (see text). The treatment is shown on the side of each image series. The cerebellum is outlined with a dotted line in the left panels; the arrowheads point out two neoplastic outgrowths. A sagittal section around the midline is shown in the middle panels; neurons and neuronal precursors are visualized by Nissl staining. The boxed regions are shown at high magnification in the right panels; arrows indicate the EGL.