In vitro polymerization of tau protein monitored by laser light scattering: Method and application to the study of FTDP-17 mutants

Tau polymerization into the filaments that compose neurofibrillary tangles is seminal to the development of many neurodegenerative diseases. It is the refore important to understand the mechanisms involved in this process. How ever, a consensus method for monitoring tau polymerization in vitro has bee n lacking. Here we demonstrate that illuminating tau polymerization reactio ns with laser light and measuring the increased scattering at 90 degrees to the incident beam with a digital camera results in data that closely appro ximate the mass of tau polymer formation in vitro. The validity of the tech nique was demonstrated over a range of tau concentrations and through multi ple angle scattering measurements. In addition, laser light scattering data closely correlated with quantitative electron microscopy measurements of t he mass of tau filaments. Laser light scattering was then used to measure t he efficiency with which the mutant tau proteins found in frontotemporal de mentia and Parkinsonism linked to chromosome 17 (FTDP-17) form filamentous structures. Several of these mutant proteins display enhanced polymerizatio n in the presence of arachidonic acid, suggesting a direct role for these m utations in tau the filament formation that characterizes FTDP-17.