NEURONAL EXPRESSION OF PROTEASE-NEXIN-1 MESSENGER-RNA IN RAT-BRAIN

Protease-nexin 1 (PN1), also known as glia-derived nexin, is a proteas e inhibitor secreted by cultured fibroblasts and glioma cells, with po stulated roles in regeneration and the regulation of neurite outgrowth . In this study we have localised the sites of PN1 gene expression in rat brain using in situ hybridisation. As expected, cultured cortical astrocytes contained relatively high levels of PN1 mRNA. However, the mRNA localisation in rat brain suggested that the primary sites of syn thesis in the CNS are neuronal. Relatively high levels of PN1 mRNA wer e found in the olfactory nerve layer of the olfactory bulb, in layer V of the cerebral cortex, in magnocellular neurones of the basal forebr ain, and in scattered neurones of the striatum. The results show that PN1 gene expression occurs in discrete populations of neurones in the brain, and suggest that these neurones may therefore play a role in th e local regulation of neurite outgrowth.