IN VIVO TWO PHOTON IMAGING OF ASC AGGREGATES CONFIRMS A CROSS SEEING EFFECT OF PARENCHYMAL AND VASCULAR AMYLOID-β DEPOSITION
1 Center for Neurology, University Hospital Bonn
2 Institute of Physiology II, University Hospital Bonn
3 Deutschen Rheuma-Forschungszentrums Berlin (DRFZ)
4 Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxemburg, Luxemburg
A common hallmark of almost all neurodegenerative disorders is the slow spread of protein aggregation within and between brain areas. In patients suffering Alzheimer’s disease, deposition of the protein amyloid-β correlates tightly with the activation of the innate immune system of the brain and involves inflammasome-dependent formation and release of ASC aggregates from the in microglia. ASC released by microglia could bind amyloid-β increasing the formation of amyloid-β oligomers and aggregates, acting as an inflammation-driven cross-seed for amyloid-β pathology (1). In our project, we have successfully characterized a novel mCherry-ASC reporter mouse line to monitor inflammasome formation and release of ASC aggregates in vivo. The mCherry-Pycard reporter gene was knocked into (KI) the murine Pycard gene under its native promoter, the expression and distribution of ASC (thus pyroptosomes and inflammasome formation) can be measured under endogenous conditions. We first subjected WT and mCherry-ASC mice to a basic battery of neurobehavioral tests and confirmed comparable bahavior between genotypes. We further imaged in vivo and repeatedly the cortex of mCherry-ASC mice crossed with different cell reporter lines and disease-models (mCherry-ASC x Cx3cr1-GFP, mCherry-ASC x Thy1-YFP-H and mCherry-ASC x Cx3cr1-GFP x APPswe/PSEN1dE9 respectively) using our two-photon microscope and observed that the mCherry-ASC protein was highly expressed in microglia in vivo under physiological conditions, furthermore this protein can be found in near proximity to neuronal structures and in the core of Aβ plaques of APPswe/PSEN1dE9 mice as well as in the vascular walls interacting with aggregated amyloid-β suggesting an active seeding role Venegas, C., Kumar, S., Franklin, B. S., Dierkes, T., Brinkschulte, R., Tejera, D., Vieira-Saecker, A., Schwartz, S., Santarelli, F., Kummer, M. P., Griep, A., Gelpi, E., Beilharz, M., Riedel, D., Golenbock, D. T., Geyer, M., Walter, J., Latz, E., and Heneka, M. T. (2017) Microglia-derived ASC specks cross-seed amyloid-β in Alzheimer’s disease. Nature. 552, 355–361