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

Lars Tã¶Nges,Zara D`Hedouville,Christoph P Dohm,Ã‰Va M Szegã¶,Lars Tatenhorst,Kim-Ann Saal,Sebastian Kã¼Gler,Paul Lingor,Vivian Dambeck,Patrizia Hause,Mathias Bã¤Hr,Jan Christoph Koch

doi:10.3389/fnagi.2014.00239

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.

Highlights

Since worldwide life expectancy increases, the numbers of individuals with Parkinson’s disease (PD) will strongly rise in the coming decades (Dorsey et al, 2007)
In the current study we examined whether targeted expression of either human aSyn(WT) or the A30P and A53T variants in nigral DAergic cell populations affect neurite and axonal regeneration in lesioned midbrain DAergic neurons (MDN) in vitro and in 6-OHDA-lesioned DAergic nigral neurons in vivo
In order to evaluate if expression of aSyn leads to death of DAergic cells in vitro, we transduced MDN cultures with the respective adeno-associated virus (AAV) with a titer of 1 × 108 transducing units/400,000 cells shortly after plating and quantified THimmunopositive cell numbers after 6 days

Summary

Introduction

Since worldwide life expectancy increases, the numbers of individuals with Parkinson’s disease (PD) will strongly rise in the coming decades (Dorsey et al, 2007). In brains of PD patients, alpha-synuclein (aSyn) has been found in thread-like fibrils in Lewy body deposits inside dopaminergic (DAergic) neurons and in dystrophic neurites (Spillantini et al, 1997; Del Tredici and Braak, 2012). ASyn pathology does affect DAergic cells but has been identified in other neuronal cell populations in the enteric nervous system, olfactory bulb, dorsal motor nucleus of the vagal and glossopharyngeal nerves and in other brain stem nuclei explaining the multitude of non-motor manifestations in PD (Postuma et al, 2012). ASyn is implicated in familial genetic autosomal-dominant forms of PD. There exist whole-locus multiplications or point mutations of aSyn including the A53T and the A30P variant (Singleton et al, 2013).

Methods

Results

Conclusion