Chapter 12 - Charcot–Marie–Tooth Disease

Abstract

The neurogenetic disorder Charcot–Marie–Tooth disease (CMT) encompasses a group of genetically heterogeneous, mostly non-syndromic inherited peripheral motor and sensory neuropathies. Type 1 X-linked CMT (CMT1X) is caused by over 400 mutations in the GJB1 gene, which encodes the gap junction protein connexin32 (Cx32). These mutations affect the coding and non-coding regions of GJB1 , but no definite phenotype–genotype correlation has been established in CMT1X. Cx32 is a myelin-related protein expressed by Schwann cells, oligodendrocytes and other tissues. It forms intracellular “reflexive” gap junctions between layers of the same myelinating cell in non-compact myelin in the peripheral and central nervous systems, and intercellular gap junctions in the central nervous system between oligodendrocytes and adjacent oligodendrocytes or astrocytes. Gap junctions formed by Cx32 are important in the homeostasis of myelinated axons. Models of the disease demonstrate impaired gap junction formation by mutant Cx32 and loss of Cx32 function causes peripheral neuropathy. Future research could focus on developing effective therapies for this currently incurable disease.