Charcot-Marie-Tooth disease (CMT) encompasses a group of inherited peripheral neuropathies characterized by progressive muscle weakness and sensory loss, primarily affecting the distal extremities [1]. As the most common inherited neuropathy (prevalence ~1 in 2,500), CMT results from mutations in genes essential for Schwann cell function, myelin maintenance, and axonal integrity. Schwann cells, the myelinating glia of the peripheral nervous system, play a central role in disease pathogenesis, making them critical targets for therapeutic intervention.
| Property |
Value |
| Category |
Peripheral Nervous System |
| Location |
Peripheral nerves (myelinated axons) |
| Cell Type |
Myelinating Schwann cells, Non-myelinating Schwann cells |
| Key Genes |
PMP22, MPZ, GJB1, GDA, SH3TC2, MFN2, GDAP1 |
| Inheritance |
Autosomal dominant (most common), autosomal recessive, X-linked |
| Primary Pathology |
Demyelination, axonal degeneration |
Schwann cells are the resident glial cells of the peripheral nervous system, providing essential support for neuronal function [2]:
- Myelin formation: Axonal insulation through compact myelin sheath generation
- Saltatory conduction: Enabling rapid action potential propagation via Nodes of Ranvier
- Axonal support: Metabolic exchange, neurotrophic factor secretion, and debris clearance
- Nerve repair: Dedifferentiation and remyelination following injury
- Myelinating Schwann cells: Wrap large-diameter axons (>1 micrometer) with multilamellar myelin
- Non-myelinating Schwann cells: Remak bundles, ensheathing small unmyelinated axons
- Terminal Schwann cells: Cover neuromuscular junctions
| Gene |
Protein |
Inheritance |
Notes |
| PMP22 |
Peripheral Myelin Protein 22 |
AD |
Most common (CMT1A - PMP22 duplication) |
| MPZ |
Myelin Protein Zero |
AD |
Adhesion molecule, dense line formation |
| GJB1 |
Connexin-32 |
X-linked |
Gap junctions in myelin incisures |
| SH3TC2 |
SH3 Domain and Tetratricopeptide Repeats 2 |
AR |
Endocytic recycling |
| NDRG1 |
N-myc Downstream Regulated 1 |
AR |
Cell differentiation |
| Gene |
Protein |
Inheritance |
Notes |
| MFN2 |
Mitofusin-2 |
AD |
Mitochondrial dynamics |
| GDA |
Guanine Deaminase |
AR |
Purine metabolism |
| GDAP1 |
Ganglioside-Induced Differentiation-Associated Protein 1 |
AR/AD |
Mitochondrial fission |
| AARS |
Alanyl-tRNA Synthetase |
AD |
Protein synthesis |
The primary pathological hallmark of CMT1 is abnormal myelin formation and maintenance [3]:
- PMP22 dysregulation: Overexpression leads to Schwann cell stress, abnormal myelin compaction
- Myelin breakdown: Cytoplasmic inclusions, onion bulb formation (repeated demyelination/remyelination)
- Schwann cell dedifferentiation: Reversion to immature state, loss of myelinating phenotype
- Dysregulated signaling: Impaired neuregulin-1/ERBB signaling
Secondary axonal loss is a major contributor to clinical disability:
- Wallerian-like degeneration: Axonal breakdown following demyelination
- Mitochondrial dysfunction: Energy failure in distal axons
- Neurotrophic factor deprivation: Reduced support from dysfunctional Schwann cells
- Calcium dysregulation: Proteolytic axonal degeneration
¶ Autophagy and ER Stress
Emerging evidence suggests:
- Impaired autophagy: Accumulation of damaged organelles
- ER stress: Unfolded protein response activation
- Oxidative stress: Increased reactive oxygen species
- Distal weakness: Ankle dorsiflexion (foot drop) -> steppage gait
- Proximal progression: Gradual spread to hands and forearms
- Muscle atrophy: Particularly in calves ("stork leg" appearance)
- Foot deformities: Pes cavus, hammertoes
- Distal sensory loss: Stocking-glove distribution
- Reduced proprioception: Sensory ataxia, especially in darkness
- Neuropathic pain: Burning or tingling sensations
- Tremor: Postural tremor in hands
- Reduced reflexes: Absent ankle jerks early
- Scoliosis: In some patients
| Strategy |
Target |
Status |
| Antisense oligonucleotides |
PMP22 |
Preclinical |
| Gene silencing (RNAi) |
PMP22 |
Preclinical |
| Gene replacement |
GJB1 |
Preclinical |
| Small molecule correctors |
MPZ, PMP22 |
Preclinical |
- Neurotrophic factors: BDNF, GDNF delivery
- Antioxidants: Vitamin E, CoQ10
- Actin stabilization: Hydroxyamidine compounds
- mTOR inhibitors: Rapamycin for autophagy enhancement
- Physical therapy: Maintaining mobility, preventing contractures
- Orthopedic interventions: Ankle-foot orthoses, surgical correction
- Pain management: Anticonvulsants, antidepressants
- Assistive devices: Canes, walkers in advanced cases
- Hattori N, Yamamoto M, Yoshihara T, et al. Demyelinating and axonal features of Charcot-Marie-Tooth disease with myelin protein zero (MPZ) gene mutations. Brain. 2003;126(Pt 10):2093-2104.
- Nave KA, Trapp BD. Axon-glial signaling and the glial support of axon function. Annu Rev Neurosci. 2008;31:535-561.
- Scherer SS, Wrabetz L, Feltri ML. Molecular mechanisms of inherited demyelinating neuropathies. Glia. 2008;56(14):1478-1489.
- Pareyson D, Saveri P, Sagnelli A, Piscosquito G. Mitochondrial dynamics and inherited peripheral neuropathies. Neuromuscul Disord. 2015;25(7):554-564.