miR-381 Attenuates Peripheral Neuropathic Phenotype Caused by Overexpression of PMP22

Charcot-Marie Tooth disease type 1A (CMT1A), the major type of CMT, is caused by duplication of peripheral myelin protein 22 (PMP22) gene whose overexpression causes structural and functional abnormalities in myelination. We investigated whether miRNA-mediated regulation of PMP22 expression could reduce the expression level of PMP22, thereby alleviating the demyelinating neuropathic phenotype of CMT1A. We found that several miRNAs were down-regulated in C22 mouse, a CMT1A mouse model. Among them, miR-381 could target 3′ untranslated region (3′UTR) of PMP22 in vitro based on Western botting and quantitative Real Time-PCR (qRT-PCR) results. In vivo efficacy of miR-381 was assessed by administration of LV-miR-381, an miR-381 expressing lentiviral vector, into the sciatic nerve of C22 mice by a single injection at postnatal day 6 (p6). Administration of LV-miR-381 reduced expression level of PMP22 along with elevated level of miR-381 in the sciatic nerve. Rotarod performance analysis revealed that locomotor coordination of LV-miR-381 administered C22 mice was significantly enhanced from 8 weeks post administration. Electrophysiologically, increased motor nerve conduction velocity was observed in treated mice. Histologically, toluidine blue staining and electron microscopy revealed that structural abnormalities of myelination were improved in sciatic nerves of LV-miR-381 treated mice. Therefore, delivery of miR-381 ameliorated the phenotype of peripheral neuropathy in CMT1A mouse model by down-regulating PMP22 expression. These data suggest that miRNA can be used as a potent therapeutic strategy to control diseases with copy number variations such as CMT1A.

Clinical Phenotype of Peripheral Myelin Protein 22 Gene Duplication Abnormality in Charcot-Marie-Tooth Disease / 中国康复理论与实践

@#: Objective To analyse the characteristics of symptoms, signs and electrophysiology in Charcot-Marie-Tooth disease (CMT) with peripheral myelin protein 22 (PMP22) gene duplication abnormality.Methods 61 patients with CMT, 14 patients with family history and 47 sporadic patients were included. PMP22 gene duplication fragment was detected with PCR-double enzyme cutting assay. Medical history, signs were collected. Some of them received lumbar puncture and sural nerve pathological examination. Results The main clinical manifestation of the patients with PMP22 gene duplication abnormlity were asthenia of both lower extremities, especially dorsiflexion of foot, accompanied with distal atrophy (especially bilateral legs), some with upper extremity distal atrophy, ankle hyporeflexia or vanished and sensory disturbance. Protein in cerebrospinal fluid may increase, giant potential and conduction velocity of sensory and motor nerve decreased. Sural nerve biopsies revealed demyelination accompanied with axonal degeneration.Conclusion The main clinical manifestation of patients with PMP22 gene duplication abnormlity is charactered as the distal atrophy and asthenia of lower limbs, accompanied with sensory abnormlity. Myelin sheath and axonal alteration were found in electromyogram and peripheral nerve pathology.