Clinical, laboratory, and genetic studies of families with Charcot-Marie-Tooth type 2C disease.
Doctoral thesis, UCL (University College London).
Charcot-Marie-Tooth disease type 2C (CMT2C) is an autosomal dominant neuropathy characterized by limb, diaphragm, and laryngeal muscle weakness. We studied five unrelated families with CMT2C, of which two showed significant linkage to chromosome 12q24.11. Linkage analysis excluded this locus in one of the remaining families, suggesting genetic heterogeneity within this CMT subtype. SNP genotyping of samples from affected individuals in the three linked families did not reveal any deletion or copy number variation. All genes in this region were sequenced and two heterozygous missense mutations were identified in the transient receptor potential, subfamily V, member 4 (TRPV4), at positions c.805C>T and c.806G>A in two families, predicting the amino acid substitutions R269C and R269H, respectively. Two other mutations (R186Q, R232C) and one change of uncertain significance (D584N) were subsequently identified. The R269C and R269H variants were not present in more than 200 controls. TRPV4 is a well known member of the TRP superfamily of cation channels. We confirmed that it is expressed in motor and sensory neurons. The R186, R232, and R269 residues are located in the intracellular N-terminal portion of the TRPV4 protein in the ankyrin repeat domain (ARD); functional domains known to mediate protein-protein interactions. When expressed in HEK293 cells and Xenopus oocytes, R269C and R269H TRPV4 trafficked normally to the cell surface, but caused increased cell toxicity and increased constitutive and activated channel currents compared to wild-type TRPV4. Other mutations in TRPV4 have been previously associated with inherited forms of skeletal dysplasia. When mapped onto the crystal structure of the TRPV4 ARD, the mutations found in bone diseases lie on the opposite face of the domain compared to those causing neuropathy. Our findings indicate that TRPV4 mutations cause a degenerative disorder of peripheral nerves. Thus, there is striking phenotypic variability with different mutations in this important channel protein.
|Title:||Clinical, laboratory, and genetic studies of families with Charcot-Marie-Tooth type 2C disease|
|Open access status:||An open access version is available from UCL Discovery|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Medical Sciences > Medicine (Division of)|
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