COMPARATIVE DISTRIBUTION OF MYRISTOYLATED-ALANINE-RICH-C-KINASE-SUBSTRATE (MARCKS) AND F1 GAP-43 GENE-EXPRESSION IN THE ADULT-RAT BRAIN/

Myristoylated alanine-rich C-kinase substrate (MARCKS) and F1/GAP-43 ( B-50/ neuromodulin) are both major specific substrates for protein kin ase C (PKC) and appear to play an important role in the regulation of neuroplastic events during development and in the adult brain. Since P KC isozymes are differentially expressed in brain and the expression o f F1/GAP-43 and MARCKS mRNAs are differentially regulated by PKC throu gh posttranslational mechanisms, the present study examined the relati ve distribution of both mRNAs in the adult rat brain by using in situ hybridization histochemistry. MARCKS hybridization was most pronounced in the olfactory bulb, piriform cortex (layer II) medial habenular nu cleus, subregions of the amygdala, specific hypothalamic nuclei, hippo campal granule cells, neocortex, and cerebellar cortex, intermediate i n the superior colliculus, hippocampal CAI, and certain brainstem nucl ei including the locus coeruleus, and low-absent in regions of the cau date-putamen, geniculate nuclei, thalamic nuclei, lateral habenular nu cleus, and hippocampal CA3 pyramidal and hilar neurons. Consistent wit h previous reports, prominent F1/GAP-43 hybridization was observed in neocortex, medial geniculate, piriform cortex (layer II), substantia n igra pars compacts, hippocampal CA3 pyramidal cells, thalamic and hypo thalamic nuclei, lateral habenular nucleus, locus coeruleus, raphe nuc lei, and cerebellar granule calls, intermediate in regions of the thal amus, hypothalamus, and amygdala, and low-absent in regions of tile ol factory bulb, caudate-putamen, medial habenular nucleus, hippocampal g ranule cells, and superior colliculus. Overall, F1/GAP-43 a as highly expressed in a greater number of regions compared to MARCKS and, in a number of regions, including the hippocampus, habenular complex, ventr al tegmentum, geniculate, and certain brain stem nuclei, a striking in verse pattern of expression Tvas observed. These results indicate that MARCKS gene expression, like that of F1/GAP-43, remains elevated in s elect regions of the adult rat brain which are associated with a high degree of retained plasticity. The potential role of PKC in the regula tion of MARCKS and F1/GAP-43 gene expression in brain is assessed. (C) 1997 Wiley-Liss, Inc.