Neuronal apoptosis in the developing cerebellum.

The following study analysed apoptosis in proliferative cells and migrating neurons of the developing cerebellum. The external granular layer, Purkinje cell layer and internal granular layer in the developing mouse cerebellar cortex were analysed by active caspase-3 immunohistochemistry, Hoechst 33258 staining and Western blot analysis. Immunocytochemistry results indicated that the peak of apoptosis appeared at postnatal days P8, P5 and P9 in the external granular layer, Purkinje cell layer and internal granular layer, respectively. Subsequently, in each region, the rate of apoptosis decreased with increasing age. In contrast, Western blot results demonstrated the highest expression of activated caspase-3 in the cerebellum at P5, followed by a subsequent decline and disappearance of expression by P14. Activated caspase-8 was expressed maximally at P10, and subsequently disappeared by P30. The results of this study suggest that the key period of neuronal apoptosis in the cerebellar cortex is between P0 and P14, indicating that this developmental period could be susceptible to treatment for congenital neurodegenerative diseases.