title: TRPV4 mutations and cytotoxic hypercalcemia in axonal Charcot-Marie-Tooth neuropathies.
abstract: OBJECTIVE
  To improve understanding of TRPV4-associated axonal Charcot-Marie-Tooth (CMT) neuropathy phenotypes and their debated pathologic mechanism.
  
  
  METHODS
  A total of 17 CMT2C phenotypic families with vocal cord and diaphragmatic involvement and 36 clinically undifferentiated CMT2 subjects underwent sequencing analysis of the coding region of TRPV4. Functional studies of mutant proteins were performed using transiently transfected cells for TRPV4 subcellular localization, basal and stimulated Ca(2+) channel analysis, and cell viability assay with or without channel blockade.
  
  
  RESULTS
  Two TRPV4 mutations R232C and R316H from 17 CMT2C families were identified in the ankyrin repeat domains. The R316H is a novel de novo mutation found in a patient with CMT2C phenotype. The family with R232C mutation had individuals with and without vocal cord and diaphragm involvement. Both mutant TRPV4 proteins had normal subcellular localization in HEK293 and HeLa cells. Cells transfected with R232C and R316H displayed increased intracellular Ca(2+) levels and reversible cell death by the TRPV channel antagonist, ruthenium red.
  
  
  CONCLUSIONS
  TRPV4 ankyrin domain alterations including a novel de novo mutation cause axonal CMT2. Individuals with the same mutation may have nondistinct CMT2 or have phenotypic CMT2C with vocal cord paresis. Reversible hypercalcemic gain-of-function of mutant TRPV4 instead of loss-of-function appears to be pathologically important. The reversibility of cell death by channel blockade provides an attractive area of investigation in consideration of treatable axonal degeneration.
authors.affiliation: Department of Neurology and Division of Peripheral Nerve Diseases, Mayo Clinic Foundation, Rochester, MN 55905, USA. klein.christopher@mayo.edu
authors.forename: C J
authors.initials: CJ
authors.lastname: Klein
authors.forename: Y
authors.initials: Y
authors.lastname: Shi
authors.forename: F
authors.initials: F
authors.lastname: Fecto
authors.forename: M
authors.initials: M
authors.lastname: Donaghy
authors.forename: G
authors.initials: G
authors.lastname: Nicholson
authors.forename: M E
authors.initials: ME
authors.lastname: McEntagart
authors.forename: A H
authors.initials: AH
authors.lastname: Crosby
authors.forename: Y
authors.initials: Y
authors.lastname: Wu
authors.forename: H
authors.initials: H
authors.lastname: Lou
authors.forename: K M
authors.initials: KM
authors.lastname: McEvoy
authors.forename: T
authors.initials: T
authors.lastname: Siddique
authors.forename: H-X
authors.initials: HX
authors.lastname: Deng
authors.forename: P J
authors.initials: PJ
authors.lastname: Dyck
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000235:genetics; D000818:Animals; D001369:Axons / Q000473:pathology*; D002118:Calcium / Q000378:metabolism; D002461:Cell Line, Transformed; D002470:Cell Survival; D002607:Charcot-Marie-Tooth Disease / Q000150:complications / Q000235:genetics / Q000473:pathology; D003964:Diaphragm / Q000473:pathology*; D005192:Family Health; D006801:Humans; D006934:Hypercalcemia / Q000209:etiology* / Q000235:genetics; D007424:Intracellular Fluid / Q000378:metabolism; D008297:Male; D009154:Mutation / Q000235:genetics*; D012430:Ruthenium Red / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000235:genetics*; D014162:Transfection / Q000379:methods
chemical_list: D000596:Amino Acids; D050916:TRPV Cation Channels; C416986:TRPV4 protein, human; D012430:Ruthenium Red; D002118:Calcium