SR13 PMP-22 EXPRESSION IN RAT NERVOUS-SYSTEM, IN PC12 CELLS, AND C6 GLIAL-CELL LINES/

SR13/PMP-22 is a protein that was identified after screening a sciatic nerve cDNA library. Our study focused on comparing the level and patt ern of expression of SR13/PMP-22 protein and RNA. Northern blot analys is revealed that although SR13/PMP-22 mRNA was present in all nervous tissues and cells studied, levels were at least seven fold higher in t he sciatic nerve and the spinal cord. During sciatic nerve postnatal d evelopment and maturation, the SR13/PMP-22 mRNA was detected at 2 days after birth, reached a maximal level at day 24, and decreased to 1/3 of the maximum in adult animals. Nerve transection reduced the level o f SR13/PMP-22 mRNA to less than 5% in the segment distal to the nerve injury. Experiments using in situ hybridization localized the SR13/PMP -22 mRNA in Schwann cells. Schwann cells present in the vicinity or di stal to the nerve cut repressed the signal for the message. In situ hy bridization experiments also demonstrated that dorsal root ganglia sat ellite cells contained the message for SR13/PMP-22. The SR13/PMP-22 an tisera used in our study showed a complex pattern of staining. As expe cted, the SR13/PMP-22 antibody peptide 1 immunoreacted with the sciati c nerve sheath. However, immunocytochemistry of the dorsal root gangli a revealed that the staining was contained in the neuron's cell body a nd processes and also in satellite cells. We also identified immunorea ctive cell bodies and fibers in the spinal cord dorsal horn. Tissue cu lture studies demonstrated that SR13/PMP-22 mRNA is induced in NGF tre ated PC12 but not in C6 glioma cell lines grown under experimental con ditions that stimulated cell growth arrest. Our experiments suggest th at SR13/PMP-22 may have some other function(s) in addition to its hypo thesized role in peripheral myelination. (C) 1994 Wiley-Liss, Inc.