rAAV2/7 vector-mediated overexpression of alpha-synuclein in mouse substantia nigra induces protein aggregation and progressive dose-dependent neurodegeneration

Abstract

BackgroundAlpha-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.ResultsWe 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.ConclusionsIn 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.

Comparison between α-synuclein wild-type and A53T mutation in a progressive Parkinson's disease model

“…Recently, a study using rAAV2/7 to express α-synuclein in SNpc showed the immunofluorescence of α-synuclein, but the results only showed the data of 5 day and 8 week, and it's cannot illustrate the expression level of α-synuclein [17]. In our study, we used the immunohistochemistry to stain α-synuclein in SNpc and the results showed the progress of α-synuclein expression.…”

Leucine-rich Repeat Kinase 2 (LRRK2) Pharmacological Inhibition Abates α-Synuclein Gene-induced Neurodegeneration

“…Acute overexpression of ␣-synuclein in SNpc neurons results in the accumulation of nitrosylated/oxidized ␣-synuclein in the soma of surviving dopaminergic neurons 4 weeks post-viral transduction (15,16,23). Analysis of serial brain sections for nitrosylated/oxidized ␣-synuclein demonstrated abundant abnormal ␣-synuclein in the soma of surviving THϩ neurons in both G2019Sϩ and G2019SϪ rats (Fig.…”

“…The recombinant adeno-associated viral (rAAV) ␣-synuclein overexpression model of PD faithfully induces dopaminergic neurodegeneration in mice, rats, and non-human primates (14,15). We found previously that LRRK2 knockout rats are protected from neurodegeneration (16).…”

“…The timeline for dopaminergic neurodegeneration in this model system has been established previously (15,16,20). We first evaluated rats 2 weeks post-viral transduction for human ␣-synuclein expression, before the onset of neurodegeneration.…”

Development of an Alpha-synuclein Based Rat Model for Parkinson's Disease via Stereotactic Injection of a Recombinant Adeno-associated Viral Vector

“…The method described can also be used to develop a rAAV2/7 α-SYN based mice model for Parkinson's disease 24 . In mice we inject a volume of 2 µl rAAV vector in the SN.…”