Background TRPV4 mutations have been identified in Charcot–Marie–Tooth type 2 (CMT2), scapuloperoneal spinal muscular atrophy and distal hereditary motor neuropathy (dHMN).
Objective We aimed to screen the TRPV4 gene in 422 British patients with inherited neuropathy for potentially pathogenic mutations.
Methods We sequenced TRPV4 coding regions and splice junctions in 271 patients with CMT2 and 151 patients with dHMN. Mutations were clinically and genetically characterised and screened in ≥345 matched controls.
Results 13 missense and nonsense variants were identified, of which five were novel and absent from controls (G20R, E218K, N302Y, Y567X and T701I). N302Y and T701I mutations were present in typical CMT2 cases and are potentially pathogenic based on in silico analyses. G20R was detected in a patient with dHMN and her asymptomatic father and is possibly pathogenic with variable expressivity. The Y567X variant segregated with disease in a family with severe CMT2 but also with a MFN2 mutation reported to cause a mild CMT2 phenotype. Although Y567X caused nonsense mediated mRNA decay, the amount of TRPV4 protein on western blotting of patient lymphoblasts was no different to control. Y567X is therefore unlikely to be pathogenic. E218K is unlikely to be pathogenic based on segregation.
Conclusions In this comprehensive analysis of the TRPV4 gene, we identified mutations in <1% of patients with CMT2/dHMN. We found that TRPV4 likely harbours many missense and nonsense non-pathogenic variants that should be analysed in detail to prove pathogenicity before results are given to patients.
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Funding MMR and HH are grateful to the Medical Research Council (MRC) and the Muscular Dystrophy Campaign, and SM and MMR are grateful to the NINDS/ORD (1U54NS065712-01) for their support. SW is funded by an Alzheimer's Research UK fellowship. We would also like to thank The Wellcome Trust for financial support to HH. This work was undertaken at University College London Hospitals/University College London, which received a proportion of funding from the Department of Health's National Institute for Health Research Biomedical Research Centres funding scheme.
Competing interests RQ was a principal investigator for a drug trial sponsored by PTC therapeutics. She has received research grants from the Muscular Dystrophy Campaign, Action Research and AGSD, and has received lecture fees from Genzyme.
Ethics approval Ethics approval was provided by UCLH/UCL Institute of Neurology.
Provenance and peer review Not commissioned; externally peer reviewed.