Abstract
ABSTRACTBackgroundMyoclonus‐dystonia is a neurogenic movement disorder caused by mutations in the gene encoding ɛ‐sarcoglycan. By contrast, mutations in the α‐, β‐, γ‐, and δ‐sarcoglycan genes cause limb girdle muscular dystrophies. The sarcoglycans are part of the dystrophin‐associated protein complex in muscle that is disrupted in several types of muscular dystrophy. Intriguingly, patients with myoclonus‐dystonia have no muscle pathology; conversely, limb‐girdle muscular dystrophy patients have not been reported to have dystonia‐associated features. To gain further insight into the molecular mechanisms underlying these differences, we searched for evidence of a sarcoglycan complex in the brain.MethodsImmunoaffinity chromatography and mass spectrometry were used to purify ubiquitous and brain‐specific ɛ‐sarcoglycan directly from tissue. Cell models were used to determine the effect of mutations on the trafficking and assembly of the brain sarcoglycan complex.ResultsUbiquitous and brain‐specific ɛ‐sarcoglycan isoforms copurify with β‐, δ‐, and ζ‐sarcoglycan, β‐dystroglycan, and dystrophin Dp71 from brain. Incorporation of a muscular dystrophy‐associated β‐sarcoglycan mutant into the brain sarcoglycan complex impairs the formation of the βδ‐sarcoglycan core but fails to abrogate the association and membrane trafficking of ɛ‐ and ζ‐sarcoglycan.Conclusionsɛ‐Sarcoglycan is part of the dystrophin‐associated protein complex in brain. Partial preservation of ɛ‐ and ζ‐sarcoglycan in brain may explain the absence of myoclonus dystonia‐like features in muscular dystrophy patients. © 2016 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.
Highlights
The involvement of SGCE in the genetic etiology of Myoclonus dystonia (M-D) is well established, little is known about the function of E-sarcoglycan and the other sarcoglycans in the brain including whether the proteins physically associate to form a stable protein complex
Having demonstrated that some of the sarcoglycans are expressed in the brain, Western blots were used to determine whether a cognate protein was present
To better understand the role of E-sarcoglycan in M-D, we aimed to establish whether a sarcoglycan complex exists in the brain
Summary
To better understand the role of E-sarcoglycan in M-D, we aimed to establish whether a sarcoglycan complex exists in the brain
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