Expression of Ca²⁺/calmodulin-dependent protein kinase (CaMK) Iβ2 in developing rat CNS

We observed the onset time and distribution pattern of β2 isoform of Ca²⁺/calmodulin-dependent protein kinase I (CaMKIβ2) in the CNS of the rat during the embryonic period until birth using an immunohistochemical method. The expression of CaMKIβ2 started at embryological day 10 when the three primary brain vesicles and neural tube are generated from the neural plate. During the embryonic period, highly immunoreactive products were ubiquitously detected in neurons in the CNS, although neurons in the caudate-putamen and globus pallidus were faintly immunostained or immunonegative. High expression of CaMKIβ2 persisted in the olfactory bulb, lymbic system, neocortex, septal nuclei, amygdala complex, some hypothalamic nuclei, pontine nuclei, Purkinje cells and granule cells in the cerebellar cortex through the developing period. At the subcellular level, CaMKIβ2 was strongly expressed in nuclei of neurons but faintly in their cytoplasm, suggesting that this protein has an important role in the nuclear signaling pathway. This study demonstrates that expression of CaMKIβ2 begins at the earliest developmental stage of the rat CNS and persists through the developing period.