Distribution of PASII/PMP22 and connexin 32 proteins in the peripheral nervous system

Various mutations of PO, PASII/PMP22 and connexin 32 genes were recently reported in hereditary neuropathies, such as Charcot-Marie-Tooth disease (CMT) and Dejerine Sottas disease (DS). However, physiological roles of the proteins in PNS are not well understood. To address the functions of the proteins, we examined their localization in PNS comparatively by immunohistochemical methods. In Western blotting, a polyclonal antibody against the carboxyl terminal peptide of PASII/PMP22 reacted to 20-24 kD bands of PASII/PMP22 in mammalian PNS myelin, but produced no reaction in either mammalian or carp CNS myelin proteins. Monoclonal anti-connexin 32 antibody recognised connexin 32 of a dimer or monomer form in rat and human PNS myelin. By histological examination, PASII/PMP22 expressed dominantly in rat PNS compact myelins, while connexin 32 localized exclusively in the nodes of Ranvier, but not in compact myelins. In cell culture, axonal contact induced a remarkable increase of PASII/PMP22 in the Schwann cell in contrast to faint staining in immature Schwann cells. While localization of connexin 32 is quite different from that of PASII/PMP22, the mutations of the two proteins often induce similar phenotypes of hereditary neuropathies.