Published papers

© 2018 Elsevier Inc. The P301 L mutation in tau, a microtubule-associated protein, causes frontotemporal dementia with Parkinsonism linked to chromosome-17 (FTDP-17) that is accompanied by formation of filamentous polymers of tau. The mutation reduces the binding capability of microtubules and enhances tau filament formation. However, it is unclear whether the P301 L mutation increases the formation of the intermediates of tau filaments that are suggested to be a toxic species of tau. To determine the amount and structure of the intermediates harboring with the P301L mutation, we purified recombinant versions of wild-type, P301L, and 4 other mutants (i.e., P301S, P301T, V337M, and R406W) tau proteins and analyzed the heparin-induced aggregation of those tau constructs. We found that all of the FTDP-17 mutants increased levels of the intermediate tau oligomers. The sizes were determined by atomic force microscopy and laser light scattering. The V337M and R406W oligomers were similar in size to the wild-type, but the P301L, P301T, and P301S mutants formed smaller oligomers. In a P301L transgenic mouse model, we found tau aggregates that were similar in size to the recombinant tau oligomer. These results indicate that FTDP-17 mutations contribute to the pathogenesis via the increased formation of tau oligomers.

© 2018 Elsevier Inc. Neural network dysfunction may contribute to functional decline and disease progression in neurodegenerative disorders. Diverse lines of evidence suggest that neuronal accumulation of tau promotes network dysfunction and cognitive decline. The A152T-variant of human tau (hTau-A152T) increases the risk of Alzheimer's disease (AD) and several other tauopathies. When overexpressed in neurons of transgenic mice, it causes age-dependent neuronal loss and cognitive decline, as well as non-convulsive epileptic activity, which is also seen in patients with AD. Using intracranial EEG recordings with electrodes implanted over the parietal cortex, we demonstrate that hTau-A152T increases the power of brain oscillations in the 0.5–6 Hz range more than wildtype human tau in transgenic lines with comparable levels of human tau protein in brain, and that genetic ablation of endogenous tau in Mapt−/− mice decreases the power of these oscillations as compared to wildtype controls. Suppression of hTau-A152T production in doxycycline-regulatable transgenic mice reversed their abnormal network activity. Treatment of hTau-A152T mice with the antiepileptic drug levetiracetam also rapidly and persistently reversed their brain dysrhythmia and network hypersynchrony. These findings suggest that both the level and the sequence of tau modulate the power of specific brain oscillations. The potential of EEG spectral changes as a biomarker deserves to be explored in clinical trials of tau-lowering therapeutics. Our results also suggest that levetiracetam treatment is able to counteract tau-dependent neural network dysfunction. Tau reduction and levetiracetam treatment may be of benefit in AD and other conditions associated with brain dysrhythmias and network hypersynchrony.