Staggerer mutant mouse Purkinje cells do not contain detectable calmodulin mRNA.

Within the cerebellum calmodulin mRNA is found predominantly in Purkinje cells, with lower levels in granule cells and interneurons. The message shows developmental increases during the first 14 days postnatally. Surviving Purkinje cells of the staggerer (sg/sg) mutant, which are grossly stunted and lack tertiary dendritic spines, contain no detectable calmodulin mRNA, as assayed by Northern blot or an enhanced biotinylated in situ hybridization. This is in contrast to both the Lurcher Purkinje cells and sg/sg granule cells, which express normal levels of this mRNA up until the time they disappear. The sg/sg phenotype can be explained by a defective Purkinje-cell-specific regulatory mechanism for calmodulin.