Alpha-synuclein mutations impair axonal regeneration in models of Parkinson's disease

Abstract

The dopaminergic (DAergic) nigrostriatal tract has an intrinsic regenerative capacity which can be impaired in Parkinson's disease (PD). Alpha-synuclein (aSyn) is a major pathogenic component in PD but its impact on DAergic axonal regeneration is largely unknown. In this study, we expressed pathogenic variants of human aSyn by means of recombinant adeno-associated viral vectors in experimental paradigms of DAergic regeneration. In a scratch lesion model in vitro, both aSyn(A30P) and aSyn(A53T) significantly reduced DAergic neurite regeneration and induced loss of TH-immunopositive cells while aSyn(WT) showed only minor cellular neurotoxic effects. The striatal density of TH-immunopositive axons in the striatal 6-OHDA lesion mouse model was attenuated only by aSyn(A30P). However, striatal expression levels of the regeneration marker GAP-43 in TH-immunopositive fibers were reduced by both aSyn(A30P) and aSyn(A53T), but not by aSyn(WT), which was associated with an activation of the ROCK signaling pathway. Nigral DAergic cell loss was only mildly enhanced by additional overexpression of aSyn variants. Our findings indicate that mutations of aSyn have a strong impact on the regenerative capacity of DAergic neurons, which may contribute to their pathogenic effects.

Cellular models of alpha‐synuclein toxicity and aggregation

“…Therefore preparation of primary DAergic neurons from the ventral mesencephalon of mice has been extensively used to closely model this pathological hallmark of PD (Dryanovski et al 2013;Gaven et al 2014). Overexpression of wild-type or mutated forms of a-synuclein can be easily achieved in these models using transfection techniques (Tonges et al 2014;Hassink et al 2018) or neurons overexpressing a-synuclein can be directly cultured by preparing primary neurons from a-synuclein transgenic animals (Li et al 2013). Recently recombinant a-synuclein has been utilized to generate small seeds of pre-formed asynuclein fibrils (PFFs) and induce aggregates with characteristics of those found in diseased brains (Volpicelli-Daley et al 2014).…”

Chatting with the neighbors: crosstalk between Rho-kinase (ROCK) and other signaling pathways for treatment of neurological disorders

“…Supporting this, toxin-induced dopaminergic neurodegeneration, classically employed as PD model, is dependent on alpha-synuclein abundance: Knock-out mice were resistant to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrine (MPTP)-induced toxicity of dopaminergic cells (Dauer et al, 2002 ). Importantly, mutant alpha-synuclein transduced neuronal cultures as well as MPTP-based in vivo models displayed a hyper-active ROCK-signaling axis, emphasizing ROCK-upregulation as a common mechanism of genetic and toxin-induced PD-models (Barcia et al, 2012 ; Villar-Cheda et al, 2012 ; Tonges et al, 2014b ).…”

Environmental and genetic factors support the dissociation between α-synuclein aggregation and toxicity

“…Preparation of primary cortical cultures from WT rats was carried out as previously described (74). Cells were treated with 1 μM of aSyn aggregates.…”