AAV2/9-mediated silencing of PMP22 prevents the development of pathological features in a rat model of Charcot-Marie-Tooth disease 1\u2009A

Benoit Gautier,Patrick Aubourg,Caroline Le Guiner,Sergio Gonzalez,Nicolas Tricaud,Claire-Maëlle Fovet,Michel Zerah,Marie Deck,Sylvia Soares,Antoine Jouvenel,Virginie François,Helene Hajjar,Maria Ceprian,Vlad Schütza,Robert Fledrich,Scarlette Abbou,Graham Campbell,Cyril Rivat,Jade Berthelot

doi:10.1038/s41467-021-22593-3

Abstract

Charcot-Marie-Tooth disease 1 A (CMT1A) results from a duplication of the PMP22 gene in Schwann cells and a deficit of myelination in peripheral nerves. Patients with CMT1A have reduced nerve conduction velocity, muscle wasting, hand and foot deformations and foot drop walking. Here, we evaluate the safety and efficacy of recombinant adeno-associated viral vector serotype 9 (AAV2/9) expressing GFP and shRNAs targeting Pmp22 mRNA in animal models of Charcot-Marie-Tooth disease 1 A. Intra-nerve delivery of AAV2/9 in the sciatic nerve allowed widespread transgene expression in resident myelinating Schwann cells in mice, rats and non-human primates. A bilateral treatment restore expression levels of PMP22 comparable to wild-type conditions, resulting in increased myelination and prevention of motor and sensory impairments over a twelve-months period in a rat model of CMT1A. We observed limited off-target transduction and immune response using the intra-nerve delivery route. A combination of previously characterized human skin biomarkers is able to discriminate between treated and untreated animals, indicating their potential use as part of outcome measures.

Highlights

Charcot-Marie-Tooth disease 1 A (CMT1A) results from a duplication of the PMP22 gene in Schwann cells and a deficit of myelination in peripheral nerves
Typical morphological characteristics of myelinating Schwann cells (mSC) were seen through GFP labeling and/or subcellular markers: Schmidt-Lanterman incisures (Supplementary Fig. S2a and b, white arrows), Cajal’s bands (Supplementary Fig. S2a, blue arrows) and paranodal loops surrounding the node of Ranvier (Supplementary Fig. S2a and c, arrowheads)
As CMT1A results from PMP22 overexpression, we looked for small hairpin inhibitory RNA (shRNA) targeting human PMP22 mRNA in order to decrease PMP22 expression in CMT1A mSC

Summary

Introduction

Charcot-Marie-Tooth disease 1 A (CMT1A) results from a duplication of the PMP22 gene in Schwann cells and a deficit of myelination in peripheral nerves. The myelin forms several successive segments named internodes, which electrically isolate the axonal membrane except at unmyelinated nodes of Ranvier where action potentials are propagated[1] This myelin sheath is critical for both motor and sensory functions in humans. The most common of these myelin-related CMT diseases is CMT1A (prevalence: 0.5–1.5/10,000)[4,5] This disease, resulting from the duplication of the PMP22 gene, is characterized by a set of heterogeneous symptoms, the most serious being feet and hands deformation and walking impairment[4]. Recent clinical trials for peripheral neuropathies, and in particular for CMT1A, have shown that the chronicity of the disease makes the evaluation of the treatment outcome very difficult

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