Purkinje cell reduction in the reeler mutant mouse: a quantitative immunohistochemical study.

We have used the immunohistochemical detection of the Purkinje cell marker cGMP-dependent protein kinase to identify Purkinje neurons in the cerebellum of the reeler mutant mouse. Our quantitative analysis of Purkinje cell number based on this marker indicates that reeler mice possess approximately 82,000 Purkinje cells, slightly less than half the number found in normal mice. Our analysis also shows that 5% of the Purkinje cells in reeler are located in a normal position (between molecular and granular layers), 10% are found in the granular layer, and the remainder form the deep cellular masses characteristic of the reeler cerebellum. The finding of a major Purkinje cell deficit in reeler was surprising in that most investigators consider this mutation to effect cell migration as opposed to cell number. Although we cannot determine whether the Purkinje cell loss in reeler is a primary or secondary gene effect, the possibility that the reeler gene has its effect on migration through a primary effect on neurogenesis or cell survival should be considered.