Expression of neurofilament L-promoter green-fluorescent protein constructs in immortalized Schwann cell-neuron coculture

The neurofilament L/68 protein (NF-L/68) gene is expressed in the immature Schwann cell phenotype but suppressed after myelin-formation. We have inves tigated conditions which regulate the activity of the NF-L/68 promoter in g reen fluorescent protein reporter constructs expressed in the immortal rat Schwann cell strain SCL4.1/F7 in coculture with neurons. Constructs express ed in a plasmid vector containing both the full-length promoter and the 3' proximal 107 bp sequence which includes the cyclic AMP response element (CR E), were active in SCL4.1/F7 cells, but were suppressed as the cells underw ent spontaneous growth-arrest. Interaction of SCL4.1/F7 with axons accelera ted downregulation of expression from both constructs, however expression o f the full-length promoter continued in some cells until the onset of myeli n-formation. Expression of the NFL/68 construct recommenced when demyelinat ion was induced in culture by exposure to human sera from patients with par aproteinemic gammopathy. We have demonstrated a method to study the regulat ion of gene expression patterns in single Schwann cells interacting with ne urons and shown that different promoter regions may be controlled by axon-r elated and -unrelated factors. (C) 1999 Elsevier Science Ireland Ltd. All r ights reserved.