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

Cleo J. L. M. Smeets, Justyna Jezierska, Hiroyuki Watanabe, Anna Duarri Pique, Michiel R. Fokkens, Michel Meijer, Qin Zhou, Tania Yakovleva, Erik Boddeke, Wilfred den Dunnen, Jan van Deursen, Georgy Bakalkin, Harm H. Kampinga, Bart van de Sluis, Dineke S. Verbeek*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

21 Citations (Scopus)

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, a-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.

Original languageEnglish
Pages (from-to)2537-2552
Number of pages16
JournalBrain
Volume138
DOIs
Publication statusPublished - 1-Sep-2015

Keywords

  • prodynorphin
  • opioid
  • glutamate
  • neurodegeneration
  • spinocerebellar ataxia
  • LONG-TERM DEPRESSION
  • IN-VITRO
  • OPIOID-PEPTIDES
  • SYNAPTIC PLASTICITY
  • CLIMBING FIBERS
  • NMDA RECEPTORS
  • WILD-TYPE
  • MICE
  • DISEASE
  • CEREBELLUM

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