Fig. 10. Validation of microarray data by immunohistochemistry. Cryosections of neonatal (P7) cerebellum (A,D,G,J), pre-neoplastic lesions (B,E,H,K) and tumors (C,F,I,L) from patched^+/– mice were stained with primary antibodies specific for Zic3 (A-C), Pax6 (D-F), Necdin (G-I) or Hsp105 (J-L) and peroxidase-conjugated secondary antibodies. Staining was detected using the peroxidase substrate DAB, which yields a dark brown precipitate. Yellow brackets mark the boundaries of the EGL (panels A,D,G,J), pre-neoplastic (PN) regions (B,E,H,K) and tumor (C,F,I,L). Expression of all four proteins is detectable in GCPs within the EGL. Consistent with microarray data, expression of Zic3 decreases significantly in pre-neoplastic lesions and is absent from tumors; Pax6 and Necdin are restricted to peripheral regions at the pre-neoplastic stage and are undetectable in tumors; and Hsp105 expression increases markedly at the pre-neoplastic stage and decreases somewhat in tumors.