In vivo protein complementation demonstrates direct detection of presynaptic a-synuclein oligomerization and age-dependent accumulation of 8-16mer oligomer species

Intracellular accumulation of a-synuclein (a-syn) and formation of Lewy bodies are neuropathological characteristics of Parkinson's disease (PD), related a-synucleinopathies, and other neurodegenerative diseases. Recent evidence suggests that oligomerization and spreading of a-syn from neuron to neuron are key events contributing to the development of PD. To directly visualize and characterize a-syn oligomerization and spreading in vivo, we generated two independent conditional transgenic mouse models based on a-syn protein complementation assays using both split Gaussia luciferase and split Venus YFP. These inducible, neuron-specific transgenic mice allow to directly assess the quantity and subcellular distribution of a-syn oligomers in vivo. Using these innovative mouse models we demonstrate an age dependent accumulation of a specific subtype of a-syn oligomers and their synaptic localization in vivo. We provide in vivo evidence that although a-syn is found throughout neurons a-syn oligomerization takes place at the presynapse. Furthermore, our new mouse models provide strong evidence for a long distance transsynaptic cell-to-cell transfer of de novo generated a-syn oligomers in vivo. Overall design: Brain total-RNA profiles of mice were generated by RNA-Seq, in 3/4 replicates, using Illumina Hiseq-2500.