Connexin abnormality in perpharal hervons system dicease

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Connexin32 (Cx32) is a gap junction protein and its gene mutations are responsible for X-linked Charcot-Marie-Tooth disease. We examined the functional abnormality of C6 glioma cells transfected with mutant (C53S and Pl72R) Cx32 genes. Nontransfected C6 glioma cells did not express Cx32 mRNA or protein. Northern and Western blot analyzes showed Cx32 mRNA and protein in cells transfected with the wild-type gene as well as with the mutant Cx32 genes. An immunocytochemical study of cells with the wild-type gene showed that Cx32 is present in the cell membrane and cytoplasm. In cells transfected with C53S or P172R mutant gene, however, no immunoreactivity was found in the cell membrane. The scrape-loading and dye transfer method produced effective dye transfer in cells with the wild-type gene but not in those with mutant genes. A cell proliferation assay showed no differences in nontransfected cells, cells transfected with the wild-type gene and those with the mutant genes. Messenger RNA expression for myelin proteolipid protein did not change in any of these cells. These findings suggest that Cx32 gene mutation results in loss of cell-to-cell communication because of failure to incorporate Cx32 protein in the cell membrane where gap junctions are formed. The mutations do not, however, interfere with cell proliferation or myelin-specific gene expression, at least in C6 glioma cells.Cx32 mRNA and protein expression was examined using Schwann cells cultured with dorsal root ganglion neurons. The apparance of Cx32 mRNA and protein was I week after the start of culture whereas those of myelin basic protein and Po protein were 2 days after the start. The function of Cx32 appears to maintain the myelin membrane rather than to form myelin.