Fig. 4. The expression of SHH target genes is altered in the cerebellum of Pn-1-deficient mice. The distribution of Gli1, Patched 1 (Ptc1), Gli3 and Shh transcripts were examined in the cerebellum of P8 Pn-1^+/+ and Pn-1^-/- mice by in situ hybridization. Sagittal sections are shown for each gene at low (A-F) and high magnifications (G-O). The frame in G indicates the enlargements shown in H-O. The black frames in E,F indicate the enlargements shown in L,M. (A,G,H) Gli1 is expressed in the EGL and in the Bergmann glia of wild-type mice. (B,I) Gli1 expression is increased in the EGL of mutants and numbers of expressing precursors are expanded. (C,J) Wild-type Ptc1 expression. (D,K) Pn-1 deficiency induces an increase in Ptc1 expression levels and in the number of Ptc1-expressing precursors in the EGL. (E,L) Wild-type Gli3 expression. (F,M) Gli3 expression is decreased in the deeper regions of the lobes and within the EGL of mutant mice. The green frames in E,F outline zones of equal expression in both wild type and mutant. (N) Shh is predominantly expressed in the PCL of wild-type mice, and is unchanged in mutants (O). At least three independent cerebella were analysed for all genes shown and yielded identical results. EGL, external granular layer; IGL, internal granular layer; PCL, Purkinje cell layer. Scale bars: 250 µm in A for A,F; 30 µm in G; 20 µm in H for H-O.