MOLECULAR MECHANISMS AND THERAPEUTIC STRATEGIES IN CMT1 NEUROPATHIES

Charcot–Marie–Tooth (CMT) disease comprises a heterogeneous group of inherited peripheral neuropathies for which effective therapies are still lacking. Limited understanding of the molecular and developmental mechanisms underlying the most common CMT subtypes represents a major obstacle to therapeutic progress. This thesis addresses this gap by investigating two complementary aspects of CMT pathogenesis and treatment: the developmental origins of CMT1A neuropathy and a targeted therapeutic strategy for CMT1B. In the first part of the work, we explored the early structural and molecular alterations occurring in a rat model of CMT1A. Through an integrated longitudinal approach combining high-resolution lipidomics and quantitative morphometric analyses, we characterized the maturation of peripheral myelin and myelinated fibers from early postnatal stages to adulthood. We demonstrate that CMT1A nerves exhibit a profound developmental delay, evident as early as postnatal day 20, affecting both myelin lipid composition and axonal growth. CMT1A myelin fails to become enriched in long-chain sphingolipids and retains features typical of unspecialized plasma membranes. These molecular abnormalities are paralleled by defective axonal enlargement, reduced fiber diameters, and persistent hypermyelination of small-caliber axons. Together, these findings indicate that CMT1A is primarily a disorder of impaired neurodevelopment and dysmyelination rather than progressive demyelination and identify a critical temporal window for potential therapeutic intervention. In the second part, we focused on a CMT1B form caused by the dominant-negative heterozygous D61N mutation in the MPZ gene. Exploiting a knock-in mouse model faithfully recapitulating the human disease, we tested an allele-specific RNA interference strategy aimed at selectively silencing the mutant MPZ allele while preserving the wild-type. Candidate siRNA sequences were identified in vitro and are now being tested in dorsal root ganglia myelinating cultures using lentiviral vectors. Ongoing studies aim to validate functional rescue ex vivo and in vivo. Overall, this work provides novel mechanistic insight into CMT pathogenesis and establishes a translational framework for mutation-specific therapy. By revealing the developmental nature of CMT1A and advancing allele-specific silencing for CMT1B, this thesis contributes to both fundamental knowledge and therapeutic direction in the field of inherited peripheral neuropathies.