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See detailOlfactory neuron-specific expression of A30P alpha-synuclein exacerbates dopamine deficiency and hyperactivity in a novel conditional model of early Parkinson's disease stages.
Nuber, Silke; Petrasch-Parwez, Elisabeth; Arias-Carrion, Oscar et al

in Neurobiology of Disease (2011), 44(2), 192-204

Mutations in the N-terminus of the gene encoding alpha-synuclein (alpha-syn) are linked to autosomal dominantly inherited Parkinson's disease (PD). The vast majority of PD patients develop ... [more ▼]

Mutations in the N-terminus of the gene encoding alpha-synuclein (alpha-syn) are linked to autosomal dominantly inherited Parkinson's disease (PD). The vast majority of PD patients develop neuropsychiatric symptoms preceding motor impairments. During this premotor stage, synucleinopathy is first detectable in the olfactory bulb (OB) and brain stem nuclei; however its impact on interconnected brain regions and related symptoms is still less far understood. Using a novel conditional transgenic mouse model, displaying region-specific expression of human mutant alpha-syn, we evaluated effect and reversibility of olfactory synucleinopathy. Our data showed that induction of mutant A30P alpha-syn expression increased transgenic deposition into somatodendritic compartment of dopaminergic neurons, without generating fibrillar inclusions. We found reversibly reduced levels of dopamine and metabolites in the OB, suggesting an impact of A30P alpha-syn on olfactory neurotransmitter content. We further showed that mutant A30P expression led to neurodegenerative changes on an ultrastructural level and a behaviorally hyperactive response correlated with novelty, odor processing and stress associated with an increased dopaminergic tone in midbrain regions. Our present data indicate that mutant (A30P) alpha-syn is directly implicated in reduction of dopamine signaling in OB interneurons, which mediates further alterations in brain regions without transgenic expression leading functionally to a hyperactive response. These modulations of neurotransmission may underlie in part some of the early neuropsychiatric symptoms in PD preceding dysfunction of the nigrostriatal dopaminergic system. [less ▲]

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See detailTransgenic overexpression of the alpha-synuclein interacting protein synphilin-1 leads to behavioral and neuropathological alterations in mice.
Nuber, Silke; Franck, Thomas; Wolburg, Hartwig et al

in Neurogenetics (2010), 11(1), 107-20

Synphilin-1 has been identified as an interacting protein of alpha-synuclein, Parkin, and LRRK2, proteins which are mutated in familial forms of Parkinson disease (PD). Subsequently, synphilin-1 has also ... [more ▼]

Synphilin-1 has been identified as an interacting protein of alpha-synuclein, Parkin, and LRRK2, proteins which are mutated in familial forms of Parkinson disease (PD). Subsequently, synphilin-1 has also been shown to be an intrinsic component of Lewy bodies in sporadic PD. In order to elucidate the role of synphilin-1 in the pathogenesis of PD, we generated transgenic mice overexpressing wild-type and mutant (R621C) synphilin-1 driven by a mouse prion protein promoter. Transgenic expression of both wild-type and the R621C variant synphilin-1 resulted in increased dopamine levels of the nigrostriatal system in 3-month-old mice. Furthermore, we found pathological ubiquitin-positive inclusions in cerebellar sections and dark-cell degeneration of Purkinje cells. Both transgenic mouse lines showed significant reduction of motor skill learning and motor performance. These findings suggest a pathological role of overexpressed synphilin-1 in vivo and will help to further elucidate the mechanisms of protein aggregation and neuronal cell death. [less ▲]

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