Fig. 1. (A) tPA mRNA is expressed in both Purkinje cells (P) and granule cells (G) in mouse cerebellum during development. In situ hybridization was performed on wild-type mouse cerebellum at P12 using tPA antisense mRNA probes corresponding to either nucleotides 977-1409 of the tPA-coding region (shown), or 1890-2401 of the tPA 3' untranslated region (not shown). Identical patterns of expression were observed for the probes. No specific expression above background was detected when the corresponding sense probes were used. Scale bars: 100 µm (left); 20 µm (right). (B) Increased tPA activity in Lurcher cerebella at P12 but not P30. The amidolytic assay was performed as described in Materials and Methods. Notice that the level of tPA activity in the cerebella of Lc/+ at P12 was significantly higher than in wild-type mice, but no significant difference was detected at P30. The data are presented as mean±s.e.m. (n=4 or 5 mice). *P<0.05 by ANOVA.