LETTERS Mutations in TRPV4 cause Charcot-Marie-Tooth disease type 2C Guida Landouré1–4,12, Anselm A Zdebik1,2,12, Tara L Martinez5,6, Barrington G Burnett3, Horia C Stanescu1,2, Hitoshi Inada7, Yijun Shi3, Addis A Taye3, Lingling Kong5, Clare H Munns8,9, Shelly S Choo7, Christopher B Phelps7, Reema Paudel10, Henry Houlden10, Christy L Ludlow11, Michael J Caterina8,9, Rachelle Gaudet7, Robert Kleta1,2,13, Kenneth H Fischbeck3,13 & Charlotte J Sumner5,13 Charcot-Marie-Tooth disease type 2C (CMT2C) is an We examined subjects from two large families with CMT type autosomal dominant neuropathy characterized by limb, 2C (CMT2C) (Table 1 and Fig. 1a–f), one of which was previously diaphragm and laryngeal muscle weakness. Two unrelated reported2. As described in prior studies2–4, affected individuals families with CMT2C showed significant linkage to showed evidence of a motor greater than sensory axonal neuropathy, chromosome 12q24.11. We sequenced all genes in this causing progressive weakness of distal limb, diaphragm and laryngeal region and identified two heterozygous missense mutations muscles (Table 1). Few affected individuals complained of sensory in the TRPV4 gene, C805T and G806A, resulting in the loss, but all had reduced or absent tendon reflexes. The age of onset amino acid substitutions R269C and R269H. TRPV4 is a and severity of disease were highly variable (Table 1 and Fig. 1a). well-known member of the TRP superfamily of cation Most affected individuals reported a worsening of hand weakness in channels. In TRPV4-transfected cells, the CMT2C mutations the cold. Bilateral sensorineural hearing loss was documented in ten caused marked cellular toxicity and increased constitutive subjects, and nine subjects complained of bladder urgency and incon- and activated channel currents. Mutations in TRPV4 tinence. Muscle and nerve biopsies in a severely affected individual were previously associated with skeletal dysplasias. Our showed marked neurogenic atrophy of the gastrocnemius muscle, findings indicate that TRPV4 mutations can also cause indicating severe loss of muscle innervations (Fig. 1b) and modest a degenerative disorder of the peripheral nerves. The loss of sensory axons in the sural nerve with rare axons undergoing CMT2C-associated mutations lie in a distinct region of the degeneration (Fig. 1c–e). TRPV4 ankyrin repeats, suggesting that this phenotypic Fine mapping analysis in both families showed significant linkage © 2010 Nature America, Inc. All rights reserved. All rights Inc. America, Nature © 2010 variability may be due to differential effects on regulatory to chromosome 12q24.11–12q24.21 (log10 of odds (lod) scores 3.1 protein-protein interactions. and 6.9, respectively), confirming the findings of previous studies4,5. Haplotype reconstruction matched the disease status in all clinically Motor and sensory peripheral nerve cells are highly specialized, affected subjects. Two individuals in family 1 carried the disease allele with long axons that connect the spinal cord with the periphery. but were not found to be affected during limited examination in their Like all neurons, these cells are excitable and depend on ion channels homes. Combined data from families 1 and 2 narrowed the region for multiple functions, including action-potential propagation, syn- of interest to a 2.6-Mb interval between the markers D12S105 and aptic transmission, plasticity and cell survival. Charcot-Marie-Tooth D12S1343 (Fig. 1g). SNP array analysis showed no duplications or (CMT) disease (or hereditary motor and sensory neuropathy, HMSN) deletions in this region (data not shown). is a heterogeneous group of degenerative peripheral nerve disorders Sequencing of all 38 predicted protein-coding genes in the region that together constitute the most common inherited neurological of interest revealed heterozygous nucleotide variants C805T and disease, with an incidence of 1 in 2,500 (ref. 1). In CMT, progressive G806A in exon 5 of the transient receptor potential vanilloid 4 axonal degeneration and cell death result in disabling muscle weak- (TRPV4) gene in affected family members of families 1 and 2, ness and sensory loss. respectively (Fig. 1h). These sequence variants were not present 1Department of Medicine and 2Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK. 3Neurogenetics Branch, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA. 4Service de Neurologie, Centre Hospitalo- Universitaire du Point ‘G’, Université de Bamako, Bamako, Mali. 5Department of Neurology, Johns Hopkins University, Baltimore, Maryland, USA. 6W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA. 7Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA. 8Department of Biological Chemistry and 9Department of Neuroscience, Center of Sensory Biology, Johns Hopkins University, Baltimore, Maryland, USA. 10University College London, Institute of Neurology, London, UK. 11Laboratory of Neural Bases of Communication and Swallowing, James Madison University, Harrisonburg, Virginia, USA. 12These authors contributed equally to this work. 13These authors jointly directed the project. Correspondence should be addressed to C.J.S. ([email protected]). Received 5 October; accepted 3 December; published online 27 December 2009; doi:10.1038/ng.512 170 VOLUME 42 | NUMBER 2 | FEBRUARY 2010 NATURE GENETICS LETTERS Table 1 Phenotypic characteristics of subjects with CMT2C Age of Limb weakness Patient Age (yr) Sex onset (yr) First symptom Vocal fold paresis Proximal Distal Sensory loss Hearing loss F1 III2 71 F 44 Foot weakness Mild None Moderate Minimal Yes F1 IV2 48 F 5 Foot weakness Moderate Mild Severe Mild No F1 IV3 46 F 5 Stridor Moderate Mild Moderate Mild No F1 IV4 44 F 3 Foot weakness Severe Severe Severe Moderate Yes F1 V1 24 F 7 Foot weakness ND None Mild Mild No F1 V3 20 F 5 Stridor ND None Mild Mild No F1 V8 18 M 2 Stridor Severe None Mild Minimal No F2 III11 65 M 57 Hearing loss Mild None Mild Minimal Yes F2 III18 61 M 34 Foot weakness Mild Mild Moderate Minimal Yes F2 III22 64 F 35 Foot weakness Mild Mild Severe Minimal Yes F2 III23 57 F 22 Foot weakness Moderate None Mild Minimal Yes F2 III24 49 F <2 Stridor Moderate Mild Moderate Mild Yes F2 IV2 50 M 16 Hoarseness Mild Mild Moderate Mild Yes F2 IV5 53 M 28 Hoarseness Moderate None Mild Minimal Yes F2 IV9 31 F 5 Stridor Moderate None Mild None No F2 IV10 29 M 5 Hoarseness Moderate None Mild Minimal Yes F2 IV12 29 F 2 Stridor Severe Moderate Severe Mild No ND, not determined. in 209 ethnically matched unaffected control individuals. The identi- other families with a CMT2C-like phenotype failed to identify fied mutations predict substitutions at the same amino acid (R269C any mutations, and in one, linkage to chromosome 12q24.11 was and R269H) in the TRPV4 protein. This residue is conserved across excluded, suggesting that CMT2C may be genetically heterogeneous multiple vertebrate species (Fig. 1i). Sequencing of TRPV4 in two (Supplementary Fig. 1). Figure 1 Phenotypic and genetic a F1.III.2 F1.IV.4 b c characteristics of CMT2C. (a) Marked variability of disease severity is demonstrated by mild, late-onset weakness in subject F1.III.2, but severe quadriparesis and respiratory failure in her daughter, subject d e F1.IV.4. Written consent was obtained to publish these photographs. (b) Light microscope images of hematoxylin and eosin-stained sections of gastrocnemius muscle biopsy from subject F1.IV.4 © 2010 Nature America, Inc. All rights reserved. All rights Inc. America, Nature © 2010 demonstrating profound denervation atrophy f Family 1 1 2 Family 2 1 2 of muscle. Scale bar, 10 µm. (c) Toluidine I. I. blue–stained section of sural nerve shows mild loss of large, myelinated sensory 1* 2 3 4 5 6 1 2 3 4 5 6 7 8 9* II. axons. Scale bar, 10 µm. (d) Electron II. microscopy of sural nerve confirms mild loss of large and small myelinated axons 1* 2* 3 4* 5* 1 2 3 4 56* 7* 8 9 10 11*12*13*14* 15 16* 1718* 19 20* 2122*23*24* III. III. and unmyelinated axons. Scale bar, 10 µm. (e) Arrow demonstrates a rare axon undergoing 1* 2* 3* 4* 5* 6* 7* 1* 2* 3 4 5* 6* 7* 8* 9* 10* 11* 12* Wallerian-like axonal degeneration. Scale IV. IV. bar, 2 µm. (f) Pedigrees of families 1 and 2 demonstrating affected subjects in each 1* 2* 3* 4* 5* 6* 7* 8* 9*10*11* of three generations. White, unaffected; V. V. 1* black, affected; gray, unknown disease status. *Sample collected. (g) The haplotypes for g h Control i subjects F1.V.3 and F2.IV.12 are shown. TRPV4 * Family 1 defines the lower border (marker F1V3 F2IV12 Homo KHYVELLVAQGADVHAQARGRFFQPKDEG Family 1 KHYVELLVAQGADVHAQACGRFFQPKDEG D12S1343) and family 2 defines the D12S84 6 7 Family 2 KHYVELLVAQGADVHAQAHGRFFQPKDEG upper border (marker D12S105) of the D12S105 2 1 Family 1 Macaca KHYVELLVAQGADVHAQARGRFFQPKDEG D12S1583 7 5 Rattus KHYVELLVAQGADVHAQARGRFFQPKDEG region of interest. The bracket indicates D12S1339 2 4 Mus KHYVELLVAQGADVHAQARGRFFQPKDEG the linked region. (h) Sequencing shows a D12S1343 2 3 Sus KHYVELLVAQGADVHAQARGRFFQPKDEG D12S1344 1 6 Canis KHYVELLVAQGADVHAQARGRFFQPKDEG heterozygous C805T change in family 1 D12S1616 3 1 Equus KHYVELLVAQGADVHAQARGRFFQPKDEG Bos KHYVELLVAQGADVHAQARGRFFQPKDEG and a G806A change in family 2 in TRPV4. D12S145 2 2 Family 2 (i) Protein homology of TRPV4 in various D12S811 9 6 Monodelphis KHYVELLVAQGADVHAQARGRFFQPKDEG D12S1341 1 6 Gallus KHYVELLVEKGADVHAQARGRFFQPKDEG species. The mutations result in amino D12S354 4 1 Danio KQYVELLVEKGADVHAQARGRFFQPRDEG acid substitutions at Arg269, a highly D12S1023 2 2 Tetraodon KQYVELLVEKGADVHAQARGRFFQPRDEG conserved residue. NATURE GENETICS VOLUME 42 | NUMBER 2 | FEBRUARY 2010 171 LETTERS Figure 2 Mutant TRPV4 causes neuronal a 2.0 d WT R269C R269H toxicity. (a) Quantification of TRPV4 transcript Ex. 3-4 by qRT-PCR in control human lymphoblast 1.5 Ex.