title: Gain-of-function mutation in TRPV4 identified in patients with osteonecrosis of the femoral head.
abstract: Osteonecrosis of the femoral head is a debilitating disease that involves impaired blood supply to the femoral head and leads to femoral head collapse.
  
  
  
  We use whole-exome sequencing and Sanger sequencing to analyse a family with inherited osteonecrosis of the femoral head and fluorescent Ca(2+) imaging to functionally characterise the variant protein.
  
  
  
  We report a family with four siblings affected with inherited osteonecrosis of the femoral head and the identification of a c.2480_2483delCCCG frameshift deletion followed by a c.2486T>A substitution in one allele of the transient receptor potential vanilloid 4 (TRPV4) gene. TRPV4 encodes a Ca(2+)-permeable cation channel known to play a role in vasoregulation and osteoclast differentiation. While pathogenic TRPV4 mutations affect the skeletal or nervous systems, association with osteonecrosis of the femoral head is novel. Functional measurements of Ca(2+) influx through mutant TRPV4 channels in HEK293 cells and patient-derived dermal fibroblasts identified a TRPV4 gain of function. Analysis of channel open times, determined indirectly from measurement of TRPV4 activity within a cluster of TRPV4 channels, revealed that the TRPV4 gain of function was caused by longer channel openings.
  
  
  
  These findings identify a novel TRPV4 mutation implicating TRPV4 and altered calcium homeostasis in the pathogenesis of osteonecrosis while reinforcing the importance of TRPV4 in bone diseases and vascular endothelium.
authors.affiliation: Division of Hematology and Oncology, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Wayne
authors.initials: W
authors.lastname: Mah
authors.affiliation: Department of Pharmacology, University of Vermont, Burlington, Vermont, USA Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Swapnil K
authors.initials: SK
authors.lastname: Sonkusare
authors.affiliation: Division of Hematology and Oncology, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Tracy
authors.initials: T
authors.lastname: Wang
authors.affiliation: Division of Hematology and Oncology, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Bouziane
authors.initials: B
authors.lastname: Azeddine
authors.affiliation: Department of Human Genetics, McGill University, Montreal, Quebec, Canada.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Pupavac
authors.affiliation: Department of Human Genetics, McGill University, Montreal, Quebec, Canada Department of Human Genetics, McGill University and Genome Québec Innovation Centre, Montreal, Quebec, Canada.
authors.forename: Jian
authors.initials: J
authors.lastname: Carrot-Zhang
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Kwangseok
authors.initials: K
authors.lastname: Hong
authors.affiliation: Department of Human Genetics, McGill University, Montreal, Quebec, Canada Department of Human Genetics, McGill University and Genome Québec Innovation Centre, Montreal, Quebec, Canada.
authors.forename: Jacek
authors.initials: J
authors.lastname: Majewski
authors.affiliation: Department of Surgery, Division of Orthopaedic Surgery, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Harvey
authors.affiliation: Department of Human Genetics, McGill University, Montreal, Quebec, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Russell
authors.affiliation: Department of Neurology & Neurosurgery, McGill University, Montreal, Quebec, Canada.
authors.forename: Colin
authors.initials: C
authors.lastname: Chalk
authors.affiliation: Department of Human Genetics, McGill University, Montreal, Quebec, Canada.
authors.forename: David S
authors.initials: DS
authors.lastname: Rosenblatt
authors.affiliation: Department of Pharmacology, University of Vermont, Burlington, Vermont, USA Institute of Cardiovascular Sciences, University of Manchester, Manchester, UK.
authors.forename: Mark T
authors.initials: MT
authors.lastname: Nelson
authors.affiliation: Division of Hematology and Oncology, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Chantal
authors.initials: C
authors.lastname: Séguin
mesh_terms: D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism; D005260:Female; D005271:Femur Head Necrosis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D009154:Mutation; D010375:Pedigree; D016415:Sequence Alignment; D050916:TRPV Cation Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D055815:Young Adult
chemical_list: D050916:TRPV Cation Channels; C416986:TRPV4 protein, human; D002118:Calcium
keywords: TRPV4; calcium channel; novel mutation; osteonecrosis of the femoral head