Abstract:
α-Synuclein is a protein implicated in the etiopathogenesis of Parkinson’s disease (PD). AAV1/2-driven
overexpression of human mutated A53T-α-synuclein in rat and monkey substantia nigra (SN) induces degeneration
of nigral dopaminergic neurons and decreases striatal dopamine and tyrosine hydroxylase (TH). Given certain
advantages of the mouse, especially it being amendable to genetic manipulation, translating the AAV1/2-A53T
α-synuclein model to mice would be of significant value. AAV1/2-A53T α-synuclein or AAV1/2 empty vector (EV)
at a concentration of 5.16 x 1012 gp/ml were unilaterally injected into the right SN of male adult C57BL/6 mice.
Post-mortem examinations included immunohistochemistry to analyze nigral α-synuclein, Ser129 phosphorylated
α-synuclein and TH expression, striatal dopamine transporter (DAT) levels by autoradiography and dopamine levels
by high performance liquid chromatography. At 10 weeks, in AAV1/2-A53T α-synuclein mice there was a 33%
reduction in TH+ dopaminergic nigral neurons (P < 0.001), 29% deficit in striatal DAT binding (P < 0.05), 38% and
33% reductions in dopamine (P < 0.001) and DOPAC (P < 0.01) levels and a 60% increase in dopamine turnover
(homovanilic acid/dopamine ratio; P < 0.001). Immunofluorescence showed that the AAV1/2-A53T α-synuclein
injected mice had widespread nigral and striatal expression of vector-delivered A53T-α-synuclein. Concurrent
staining with human PD SN samples using gold standard histological methodology for Lewy pathology detection
by proteinase K digestion and application of specific antibody raised against human Lewy body α-synuclein (LB509)
and Ser129 phosphorylated α-synuclein (81A) revealed insoluble α-synuclein aggregates in AAV1/2-A53T α-synuclein
mice resembling Lewy-like neurites and bodies. In the cylinder test, we observed significant paw use asymmetry in the
AAV1/2-A53T α-synuclein group when compared to EV controls at 5 and 9 weeks post injection (P < 0.001; P < 0.05).
These data show that unilateral injection of AAV1/2-A53T α-synuclein into the mouse SN leads to persistent motor
deficits, neurodegeneration of the nigrostriatal dopaminergic system and development of Lewy-like pathology, thereby
reflecting clinical and pathological hallmarks of human PD.
