Conditional control of human wild-type and Parkinson's disease-associated mutant alpha-synuclein in transgenic mouse brain

Abstract

The presynaptic protein alpha-synuclein has been implicated in the pathophysiology of many neurodegenerative disorders, including Parkinson's Disease and dementia with Lewy bodies, collectively referred to as synucleinopathies. To advance the study of the function of alpha-synuclein in these diseases, we have used the tTA-system to generate transgenic mice, which express human wildtype or mutated [A30P] alpha-synuclein in a conditional manner. To obtain reversible expression of human alpha-synuclein in the brain of these mice, we combined the tTA-system with both the PrP promotor and CaMKIIalpha promotor. We investigated the conditional overexpression by western blot analysis and immunostaining of paraffin-embedded brains. Western blot analysis revealed that double-transgenic mice express alpha-synuclein at different levels in specific brain regions. The expression-pattern and level of human alpha-synuclein in the brain of double-transgenic mice depends on both the neuron-specific promotor and the integration site of the human alpha-synuclein construct. Histological analysis of the brain of transgenic mice showed aberrant expression of the protein in cell soma. However, Lewy body-like alpha-synuclein inclusions have not yet been identified. Administration of doxycycline down-regulates alpha-synuclein expression to basal levels in the brain of double-transgenic mice. We currently investigate if one transgenic mouse-line which highly expresses mutated [A30P] alpha-synuclein specifically in the olfactory bulb shows any loss of dopaminergic neurons and an impaired sense of smell. We also perform microarray expression analysis to gain insight in the pathomechanism underlying over-expression of human alpha-synuclein. Our conditional mouse-model may help to define the role of human alpha-synuclein in synucleinopathies and might be used to demonstrate whether neuropathological symptoms of these diseases are reversible.