Acquisition and Loss of a Neuronal Ca2+/Calmodulin-Dependent Protein Kinase During Neuronal Differentiation

Calcium ions play a critical role in neural development. Insights into the ontogeny of Ca2+-signaling pathways were gained by investigating the developmental expression of granule cell-enriched Ca2+/calmodulin-dependent protein kinase (CaM kinase-Gr) in the cerebellum and hippocampus of the rat. Neurons of these brain regions displayed characteristic schedules by which they acquired and lost CaM kinase-Gr during differentiation. In the cerebellum, granule cells did not begin to express CaM kinase-Gr until after birth when they migrated into the granule cell layer, and this expression persisted in the adult. Purkinje cells expressed CaM kinase-Gr prenatally and lost this expression by postnatal day 14. In contrast, the granule and pyramidal cells of the hippocampus expressed the enzyme prenatally and in the adult. Moreover, CaM kinase-Gr was localized to the processes and nuclei of developing neurons. This subcellular localization together with the scheduled expression of CaM kinase-Gr can serve to regulate a developing neuron's sensitivity to Ca2+at different subcellular levels.