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Novel HSPB1 mutation causes both motor neuronopathy and distal myopathy

Lookup NU author(s): Dr David Lewis-Smith, Dr Jennifer Duff, Dr Angela Pyle, Dr Helen Griffin, Dr Tuomo Polvikoski, Dr Daniel Birchall, Professor Rita Horvath, Professor Patrick Chinnery

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

Objective: To identify the cause of isolated distal weakness in a family with both neuropathic and myopathic features on EMG and muscle histology. Methods: Case study with exome sequencing in 2 affected individuals, bioinformatic prioritization of genetic variants, and segregation analysis of the likely causal mutation. Functional studies included Western blot analysis of the candidate protein before and after heat shock treatment of primary skin fibroblasts. Results: A novel HSPB1 variant (c.387C>G, p.Asp129Glu) segregated with the phenotype and was predicted to alter the conserved α-crystallin domain common to small heat shock proteins. At baseline, there was no difference in HSPB1 protein levels nor its binding partner αB-crystallin. Heat shock treatment increased HSPB1 protein levels in both patient-derived and control fibroblasts, but the associated increase in αB-crystallin expression was greater in patient-derived than control fibroblasts. Conclusions: The HSPB1 variant (c.387C>G, p.Asp129Glu) is the likely cause of distal neuromyopathy in this pedigree with pathogenic effects mediated through binding to its partner heat shock protein αB-crystallin. Mutations in HSBP1 classically cause a motor axonopathy, but this family shows that the distal weakness can be both myopathic and neuropathic. The traditional clinical classification of distal weakness into “myopathic” or “neuropathic” forms may be misleading in some instances, and future treatments need to address the pathology in both tissues.


Publication metadata

Author(s): Lewis-Smith DJ, Duff J, Pyle A, Griffin H, Polvikoski T, Birchall D, Horvath R, Chinnery PF

Publication type: Article

Publication status: Published

Journal: Neurology: Genetics

Year: 2016

Volume: 2

Issue: 2

Online publication date: 31/10/2016

Acceptance date: 23/08/2016

Date deposited: 06/02/2020

ISSN (electronic): 2376-7839

Publisher: AAN Publications

URL: https://doi.org/10.1212/NXG.0000000000000110

DOI: 10.1212/NXG.0000000000000110

PubMed id: 27830184


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