ULTRASTRUCTURAL DISTRIBUTION OF PMP22 IN CHARCOT-MARIE-TOOTH DISEASE TYPE 1A

Peripheral Myelin Protein-22 (PMP22) is a membrane glycoprotein which represents up to 5% of total protein in myelin of peripheral nerves. M utations affecting the PMP22 gene have been linked to the inherited pe ripheral neuropathies Charcot-Marie-Tooth disease type 1A (CMT1A; dupl ications and point mutations), Dejerine-Sottas syndrome (DSS; point mu tations), and hereditary neuropathy with liability to pressure palsies (HNPP; deletions). In this study, we determined the ultrastructural d istribution of PMP22 and other myelin proteins in normal human periphe ral nervous system (PNS) nerves and in CMT1 patients with or without t he CMT1A duplication on chromosome 17. Our results demonstrate that PM P22, P-0 protein, and myelin basic protein are present in compact myel in of all patients examined. PMP22 was also present in the plasma memb rane of Schwann cells of unmyelinated fibers and onion bulbs. Although the precise biological role of PMP22 remains to be discovered, our re sults support the hypothesis that this protein serves multiple functio ns in Schwann cells.