Gene abnormality of PMP-22 in hereditary neuropathy and its pathomechanism

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Investigation of Japanese patients with Charcot-Marie-Tooth disease (CMT) type I revealed that the most frequent gene abnormality is the duplication of PMP-22 gene. Point mutations of this gene were rare. However, Patients with point mutations tend to show severe clinical manifestations.In contrast to CMT type I, patients with hereditary neuropathy with liability to pressure palsies (NMPP) had the deletion of PMP-22 gene. Expression of PMP-22 gene in cultured fibroblasts was in proportional to its gene dosage : fibroblasts from CMT type I showed a higher and those from HNPP a lower expression than controls. Those data indicate that abnormal expression of PMP-22 gene may leads to the myelin abnormality.Some patients with CMT had point mutations of connexin (Cx) 32 gene. We showed that Cx32 is a myelin protein and its expression is under the control mechanism similar to that of Po except for the developmental profiles. We also showed that peripheral nerves contain Cx43. Their function is now studied.