title: Novel mutations highlight the key role of the ankyrin repeat domain in TRPV4-mediated neuropathy.
abstract: OBJECTIVE
  To characterize 2 novel TRPV4 mutations in 2 unrelated families exhibiting the Charcot-Marie-Tooth disease type 2C (CMT2C) phenotype.
  
  
  METHODS
  Direct CMT gene testing was performed on 2 unrelated families with CMT2C. A 4-fold symmetric tetramer model of human TRPV4 was generated to map the locations of novel TRPV4 mutations in these families relative to previously identified disease-causing mutations (neuropathy, skeletal dysplasia, and osteoarthropathy). Effects of the mutations on TRPV4 expression, localization, and channel activity were determined by immunocytochemical, immunoblotting, Ca(2+) imaging, and cytotoxicity assays.
  
  
  RESULTS
  Previous studies suggest that neuropathy-causing mutations occur primarily at arginine residues on the convex face of the TRPV4 ankyrin repeat domain (ARD). Further highlighting the key role of this domain in TRPV4-mediated hereditary neuropathy, we report 2 novel heterozygous missense mutations in the TRPV4-ARD convex face (p.Arg237Gly and p.Arg237Leu). Generation of a model of the TRPV4 homotetramer revealed that while ARD residues mutated in neuropathy (including Arg237) are likely accessible for intermolecular interactions, skeletal dysplasia-causing TRPV4 mutations occur at sites suggesting disruption of intramolecular and/or intersubunit interactions. Like previously described neuropathy-causing mutations, the p.Arg237Gly and p.Arg237Leu substitutions do not alter TRPV4 subcellular localization in transfected cells but cause elevations of cytosolic Ca(2+) levels and marked cytotoxicity.
  
  
  CONCLUSIONS
  These findings expand the number of ARD residues mutated in TRPV4-mediated neuropathy, providing further evidence of the central importance of this domain to TRPV4 function in peripheral nerve.
authors.affiliation: Department of Neurology (J.M.S., W.A., B.B., C.J.S.), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Molecular and Cellular Biology (C.M.Z., R.G.), Harvard University, Cambridge, MA; Department of Neurology (D.-H.C., T.D.B.), University of Washington School of Medicine, Seattle, WA; Department of Neurology (J.W.D., C.E.S.), Stanford Health Care, Stanford, CA; and Department of Neuroscience (C.J.S.), Johns Hopkins University, Baltimore, MD.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Sullivan
authors.affiliation: Department of Neurology (J.M.S., W.A., B.B., C.J.S.), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Molecular and Cellular Biology (C.M.Z., R.G.), Harvard University, Cambridge, MA; Department of Neurology (D.-H.C., T.D.B.), University of Washington School of Medicine, Seattle, WA; Department of Neurology (J.W.D., C.E.S.), Stanford Health Care, Stanford, CA; and Department of Neuroscience (C.J.S.), Johns Hopkins University, Baltimore, MD.
authors.forename: Christina M
authors.initials: CM
authors.lastname: Zimanyi
authors.affiliation: Department of Neurology (J.M.S., W.A., B.B., C.J.S.), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Molecular and Cellular Biology (C.M.Z., R.G.), Harvard University, Cambridge, MA; Department of Neurology (D.-H.C., T.D.B.), University of Washington School of Medicine, Seattle, WA; Department of Neurology (J.W.D., C.E.S.), Stanford Health Care, Stanford, CA; and Department of Neuroscience (C.J.S.), Johns Hopkins University, Baltimore, MD.
authors.forename: William
authors.initials: W
authors.lastname: Aisenberg
authors.affiliation: Department of Neurology (J.M.S., W.A., B.B., C.J.S.), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Molecular and Cellular Biology (C.M.Z., R.G.), Harvard University, Cambridge, MA; Department of Neurology (D.-H.C., T.D.B.), University of Washington School of Medicine, Seattle, WA; Department of Neurology (J.W.D., C.E.S.), Stanford Health Care, Stanford, CA; and Department of Neuroscience (C.J.S.), Johns Hopkins University, Baltimore, MD.
authors.forename: Breanne
authors.initials: B
authors.lastname: Bears
authors.affiliation: Department of Neurology (J.M.S., W.A., B.B., C.J.S.), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Molecular and Cellular Biology (C.M.Z., R.G.), Harvard University, Cambridge, MA; Department of Neurology (D.-H.C., T.D.B.), University of Washington School of Medicine, Seattle, WA; Department of Neurology (J.W.D., C.E.S.), Stanford Health Care, Stanford, CA; and Department of Neuroscience (C.J.S.), Johns Hopkins University, Baltimore, MD.
authors.forename: Dong-Hui
authors.initials: DH
authors.lastname: Chen
authors.affiliation: Department of Neurology (J.M.S., W.A., B.B., C.J.S.), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Molecular and Cellular Biology (C.M.Z., R.G.), Harvard University, Cambridge, MA; Department of Neurology (D.-H.C., T.D.B.), University of Washington School of Medicine, Seattle, WA; Department of Neurology (J.W.D., C.E.S.), Stanford Health Care, Stanford, CA; and Department of Neuroscience (C.J.S.), Johns Hopkins University, Baltimore, MD.
authors.forename: John W
authors.initials: JW
authors.lastname: Day
authors.affiliation: Department of Neurology (J.M.S., W.A., B.B., C.J.S.), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Molecular and Cellular Biology (C.M.Z., R.G.), Harvard University, Cambridge, MA; Department of Neurology (D.-H.C., T.D.B.), University of Washington School of Medicine, Seattle, WA; Department of Neurology (J.W.D., C.E.S.), Stanford Health Care, Stanford, CA; and Department of Neuroscience (C.J.S.), Johns Hopkins University, Baltimore, MD.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Bird
authors.affiliation: Department of Neurology (J.M.S., W.A., B.B., C.J.S.), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Molecular and Cellular Biology (C.M.Z., R.G.), Harvard University, Cambridge, MA; Department of Neurology (D.-H.C., T.D.B.), University of Washington School of Medicine, Seattle, WA; Department of Neurology (J.W.D., C.E.S.), Stanford Health Care, Stanford, CA; and Department of Neuroscience (C.J.S.), Johns Hopkins University, Baltimore, MD.
authors.forename: Carly E
authors.initials: CE
authors.lastname: Siskind
authors.affiliation: Department of Neurology (J.M.S., W.A., B.B., C.J.S.), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Molecular and Cellular Biology (C.M.Z., R.G.), Harvard University, Cambridge, MA; Department of Neurology (D.-H.C., T.D.B.), University of Washington School of Medicine, Seattle, WA; Department of Neurology (J.W.D., C.E.S.), Stanford Health Care, Stanford, CA; and Department of Neuroscience (C.J.S.), Johns Hopkins University, Baltimore, MD.
authors.forename: Rachelle
authors.initials: R
authors.lastname: Gaudet
authors.affiliation: Department of Neurology (J.M.S., W.A., B.B., C.J.S.), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Molecular and Cellular Biology (C.M.Z., R.G.), Harvard University, Cambridge, MA; Department of Neurology (D.-H.C., T.D.B.), University of Washington School of Medicine, Seattle, WA; Department of Neurology (J.W.D., C.E.S.), Stanford Health Care, Stanford, CA; and Department of Neuroscience (C.J.S.), Johns Hopkins University, Baltimore, MD.
authors.forename: Charlotte J
authors.initials: CJ
authors.lastname: Sumner