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Neurology. 2015 Aug 25;85(8):665-74. doi: 10.1212/WNL.0000000000001864. Epub 2015 Jul 24.

SQSTM1 splice site mutation in distal myopathy with rimmed vacuoles.

Author information

1
From the Department of Neurology (R.C.B., K.A., A.P., S.K.P., M.B.H., C.C.W.), Washington University School of Medicine, Saint Louis, MO; Dent Neurologic Institute (L.R.), Amherst, NY; Department of Neurogenetics (C.M.S.), Kolling Institute of Medical Research, Royal North Shore Hospital and University of Sydney, St Leonard's, New South Wales, Australia; Folkhalsan Institute of Genetics and Department of Medical Genetics (A.E., P.H., B.U.), Haartman Institute, University of Helsinki, Finland; Neuromuscular Research Center (B.U.), Tampere University Hospital and University of Tampere, Finland; and Department of Neurology (B.U.), Vaasa Central Hospital, Vaasa, Finland.
2
From the Department of Neurology (R.C.B., K.A., A.P., S.K.P., M.B.H., C.C.W.), Washington University School of Medicine, Saint Louis, MO; Dent Neurologic Institute (L.R.), Amherst, NY; Department of Neurogenetics (C.M.S.), Kolling Institute of Medical Research, Royal North Shore Hospital and University of Sydney, St Leonard's, New South Wales, Australia; Folkhalsan Institute of Genetics and Department of Medical Genetics (A.E., P.H., B.U.), Haartman Institute, University of Helsinki, Finland; Neuromuscular Research Center (B.U.), Tampere University Hospital and University of Tampere, Finland; and Department of Neurology (B.U.), Vaasa Central Hospital, Vaasa, Finland. weihlc@neuro.wustl.edu.

Abstract

OBJECTIVE:

To identify the genetic etiology and characterize the clinicopathologic features of a novel distal myopathy.

METHODS:

We performed whole-exome sequencing on a family with an autosomal dominant distal myopathy and targeted exome sequencing in 1 patient with sporadic distal myopathy, both with rimmed vacuolar pathology. We also evaluated the pathogenicity of identified mutations using immunohistochemistry, Western blot analysis, and expression studies.

RESULTS:

Sequencing identified a likely pathogenic c.1165+1 G>A splice donor variant in SQSTM1 in the affected members of 1 family and in an unrelated patient with sporadic distal myopathy. Affected patients had late-onset distal lower extremity weakness, myopathic features on EMG, and muscle pathology demonstrating rimmed vacuoles with both TAR DNA-binding protein 43 and SQSTM1 inclusions. The c.1165+1 G>A SQSTM1 variant results in the expression of 2 alternatively spliced SQSTM1 proteins: 1 lacking the C-terminal PEST2 domain and another lacking the C-terminal ubiquitin-associated (UBA) domain, both of which have distinct patterns of cellular and skeletal muscle localization.

CONCLUSIONS:

SQSTM1 is an autophagic adaptor that shuttles aggregated and ubiquitinated proteins to the autophagosome for degradation via its C-terminal UBA domain. Similar to mutations in VCP, dominantly inherited mutations in SQSTM1 are now associated with rimmed vacuolar myopathy, Paget disease of bone, amyotrophic lateral sclerosis, and frontotemporal dementia. Our data further suggest a pathogenic connection between the disparate phenotypes.

PMID:
26208961
PMCID:
PMC4553032
DOI:
10.1212/WNL.0000000000001864
[Indexed for MEDLINE]
Free PMC Article

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