Developmental regulation of neuronal expression for the eta subtype of the 14-3-3 protein, a putative regulatory protein for protein kinase C.

An in situ hybridization technique was applied to rat nervous tissues, to analyse the developmental changes in expression for the eta subtype mRNA of 14-3-3 protein, a putative regulatory protein for protein kinase C. Although signal levels of the eta subtype mRNA were low in mitotic cells in the ventricular zone, most neurons displayed a marked increase at their definitive location in the mantle zone. In general, neurons in the spinal ventral horn and peripheral ganglia showed this increase at E13-E15, those in the telencephalon, diencephalon, midbrain, pons and medulla oblongata at E18-P1, and the cerebellar Purkinje cells at P7-P14. It is at these developmental stages when neuronal differentiation including axonal and dendritic growth and ramification occurs actively. Subsequently high levels of the eta subtype mRNA were maintained until the adult stage in projection type neurons possessing larger cell bodies and highly developed dendritic fields, such as the olfactory mitral cells, hippocampal pyramidal cells, cerebellar Purkinje cells, and motor neurons in the brainstem and spinal cord. However, the signal levels decreased until the adult stage in smaller projection type neurons. On the other hand, the signal levels in local circuit type neurons were consistently low throughout development. These findings suggest that gene expression for the eta subtype mRNA of the 14-3-3 protein is regulated in close relation to both neuron types and their cytodifferentiation.