DISTRIBUTION OF THE PROTEIN-KINASE-C SUBSTRATES MARCKS AND MRP IN THEPOSTNATAL DEVELOPING RAT-BRAIN

The myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS- related protein (MRP) are both membrane-associated phosphoproteins tha t interact with calmodulin and filamentous actin in a protein kinase C phosphorylation-dependent manner. In the present study, we examined M ARCKS and MRP gene expression in the postnatal (P) rat brain (1, 7, 14 , 21, and 90 days after birth) by using quantitative in situ hybridiza tion. At P1, MRP expression was high in neocortex, striatum, thalamus, cerebellar cortex, and hippocampus (CA1-CA3, hilus, and granule cell layer) but low in brainstem and, between P7 and P14, exhibited a drama tic decline in each of these regions except hippocampal CA1 and granul e cell layers. Between P14 and P21, MRP expression increased in white matter regions including the corpus callosum, fimbria/fornix, and cere bellar deep white matter. At P90 (adult), MRP remained strongly expres sed in the olfactory bulb, medial habenula, hippocampal CA1, and the i nner two-thirds of granule cell layer, temporal, and entorhinal cortic es, the corpus callosum and fimbria/fornix, and cerebellar white matte r. At P1, MARCKS was strongly expressed in the majority of brain regio ns except the brainstem, which subsequently declined gradually to appr oximate adult levels by P14. Between P14 and P21, MARCKS expression de clined gradually in the hilus, remained elevated in hippocampal CA1, C A3, and granule cell layers, and increased dramatically in the corpus cellosum and fimbria/fornix. At P90, MARCKS expression declined in hip pocampal CA3 and hilus and remained strongly expressed in hippocampal CA1 and granule cell layers, regions of the olfactory bulb, the medial habenula, temporal cortex, and cerebellar granule and Purkinje cells. Expression of both MARCKS and MRP in regions undergoing neuronal prol iferation, migration, and neurite outgrowth suggest a common role in t hese, developmental events, whereas differences in expression during d evelopment and in the adult brain provide evidence of differential reg ulation. J. Comp. Neurol. 397.337-356, 1998. (C) 1998 Wiley-Liss, Inc.