Optimization of biosensor cell lines for the detection of tau seeding competency in human CSF

Abstract

AbstractBackgroundThe capacity of pathological tau aggregates to recruit and template monomeric tau into misfolded multimers is a major step in the propagation of tau pathology in Alzheimer’s Disease and other tauopathies. Recently, tau seeding activity in postmortem brain tissue was correlated to rate of clinical progression, confirming its relevance in the disease process. If tau seeds could be measured in biofluids, it may be an interesting novel biomarker potentially able to predict disease course. However, current available methods are not sensitive enough to quantify those seeds in the cerebrospinal fluid (CSF).MethodWe generated a series of Förster resonance energy transfer (FRET)‐based biosensor cell lines using rational design of tau bait sequences, linkers, and fluorescent reporter proteins in an attempt to increase assay sensitivity. Transient transfection was used to screen FRET efficiency of novel constructs by flow cytometry. Ultimately, multiple stable cell lines were produced and characterized for their ability to detect tau seeds in human brain lysate and lumbar CSF.ResultThe novel generation of tau biosensor cell lines demonstrated an enhanced sensitivity by more than one order of magnitude as compared to the standard reporter cell line. Tau seeding activity could be measured in less than 100 pg of human brain lysate and in microliters of lumbar CSF.ConclusionOptimized FRET‐based biosensor cells can be used to quantify tau seeds in the CSF of live individuals and are currently being implemented to test the hypothesis that seeding capability will vary in different individuals based on the characteristics of tau strains.