title: rAAV2/7 vector-mediated overexpression of alpha-synuclein in mouse substantia nigra induces protein aggregation and progressive dose-dependent neurodegeneration.
abstract: BACKGROUND
  Alpha-synuclein is a key protein implicated in the pathogenesis of Parkinson's disease (PD). It is the main component of the Lewy bodies, a cardinal neuropathological feature in the disease. In addition, whole locus multiplications and point mutations in the gene coding for alpha-synuclein lead to autosomal dominant monogenic PD. Over the past decade, research on PD has impelled the development of new animal models based on alpha-synuclein. In this context, transgenic mouse lines have failed to reproduce several hallmarks of PD, especially the strong and progressive dopaminergic neurodegeneration over time that occurs in the patients. In contrast, viral vector-based models in rats and non-human primates display prominent, although highly variable, nigral dopaminergic neuron loss. However, the few studies available on viral vector-mediated overexpression of alpha-synuclein in mice report a weak neurodegenerative process and no clear Lewy body-like pathology. To address this issue, we performed a comprehensive comparative study of alpha-synuclein overexpression by means of recombinant adeno-associated viral vectors serotype 2/7 (rAAV2/7) at different doses in adult mouse substantia nigra.
  
  
  RESULTS
  We noted a significant and dose-dependent alpha-synucleinopathy over time upon nigral viral vector-mediated alpha-synuclein overexpression. We obtained a strong, progressive and dose-dependent loss of dopaminergic neurons in the substantia nigra, reaching a maximum of 82% after 8 weeks. This effect correlated with a reduction in tyrosine hydroxylase immunoreactivity in the striatum. Moreover, behavioural analysis revealed significant motor impairments from 12 weeks after injection on. In addition, we detected the presence of alpha-synuclein-positive aggregates in the remaining surviving neurons. When comparing wild-type to mutant A53T alpha-synuclein at the same vector dose, both induced a similar degree of cell death. These data were supported by a biochemical analysis that showed a net increase in soluble and insoluble alpha-synuclein expression over time to the same extent for both alpha-synuclein variants.
  
  
  CONCLUSIONS
  In conclusion, our in vivo data provide evidence that strong and significant alpha-synuclein-induced neuropathology and progressive dopaminergic neurodegeneration can be achieved in mouse brain by means of rAAV2/7.
authors.affiliation: Department of Neurosciences and Leuven Research Institute for Neuroscience and Disease (LIND), KU Leuven, Laboratory for Neurobiology and Gene Therapy, Kapucijnenvoer 33, box 7001, 3000 Leuven, Belgium. veerle.baekelandt@med.kuleuven.be.
authors.forename: Marusela
authors.initials: M
authors.lastname: Oliveras-Salvá
authors.forename: Anke
authors.initials: A
authors.lastname: Van der Perren
authors.forename: Nicolas
authors.initials: N
authors.lastname: Casadei
authors.forename: Stijn
authors.initials: S
authors.lastname: Stroobants
authors.forename: Silke
authors.initials: S
authors.lastname: Nuber
authors.forename: Rudi
authors.initials: R
authors.lastname: D'Hooge
authors.forename: Chris
authors.initials: C
authors.lastname: Van den Haute
authors.forename: Veerle
authors.initials: V
authors.lastname: Baekelandt
mesh_terms: D000818:Animals; D015153:Blotting, Western; D000229:Dependovirus / Q000235:genetics*; D004195:Disease Models, Animal; D005260:Female; D005822:Genetic Vectors; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D009410:Nerve Degeneration / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D009474:Neurons / Q000378:metabolism / Q000473:pathology / Q000821:virology; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D013378:Substantia Nigra / Q000378:metabolism / Q000473:pathology*; D014161:Transduction, Genetic; D019076:Transgenes; D051844:alpha-Synuclein / Q000235:genetics / Q000378:metabolism*
chemical_list: D051844:alpha-Synuclein