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Brain. 2015 Sep;138(Pt 9):2537-52. doi: 10.1093/brain/awv195. Epub 2015 Jul 12.

Elevated mutant dynorphin A causes Purkinje cell loss and motor dysfunction in spinocerebellar ataxia type 23.

Author information

  • 11 Department of Genetics, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands.
  • 22 Division of Biological Research on Drug Dependence, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden.
  • 33 Department of Medical Physiology, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands.
  • 44 Department of Pathology, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands.
  • 55 Department of Paediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota, USA.
  • 66 Department of Cell Biology, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands.
  • 77 Department of Paediatrics, Molecular Genetics Section, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands.
  • 81 Department of Genetics, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands d.s.verbeek@umcg.nl.

Abstract

Spinocerebellar ataxia type 23 is caused by mutations in PDYN, which encodes the opioid neuropeptide precursor protein, prodynorphin. Prodynorphin is processed into the opioid peptides, α-neoendorphin, and dynorphins A and B, that normally exhibit opioid-receptor mediated actions in pain signalling and addiction. Dynorphin A is likely a mutational hotspot for spinocerebellar ataxia type 23 mutations, and in vitro data suggested that dynorphin A mutations lead to persistently elevated mutant peptide levels that are cytotoxic and may thus play a crucial role in the pathogenesis of spinocerebellar ataxia type 23. To further test this and study spinocerebellar ataxia type 23 in more detail, we generated a mouse carrying the spinocerebellar ataxia type 23 mutation R212W in PDYN. Analysis of peptide levels using a radioimmunoassay shows that these PDYN(R212W) mice display markedly elevated levels of mutant dynorphin A, which are associated with climber fibre retraction and Purkinje cell loss, visualized with immunohistochemical stainings. The PDYN(R212W) mice reproduced many of the clinical features of spinocerebellar ataxia type 23, with gait deficits starting at 3 months of age revealed by footprint pattern analysis, and progressive loss of motor coordination and balance at the age of 12 months demonstrated by declining performances on the accelerating Rotarod. The pathologically elevated mutant dynorphin A levels in the cerebellum coincided with transcriptionally dysregulated ionotropic and metabotropic glutamate receptors and glutamate transporters, and altered neuronal excitability. In conclusion, the PDYN(R212W) mouse is the first animal model of spinocerebellar ataxia type 23 and our work indicates that the elevated mutant dynorphin A peptide levels are likely responsible for the initiation and progression of the disease, affecting glutamatergic signalling, neuronal excitability, and motor performance. Our novel mouse model defines a critical role for opioid neuropeptides in spinocerebellar ataxia, and suggests that restoring the elevated mutant neuropeptide levels can be explored as a therapeutic intervention.

© The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

KEYWORDS:

glutamate; neurodegeneration; opioid; prodynorphin; spinocerebellar ataxia

PMID:
26169942
[PubMed - indexed for MEDLINE]
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