EVALUATION OF TAU OLIGOMERIZATION AND AGGREGATION IN P301S MICE: A LONGITUDINAL STUDY

Abstract

One of the prominent features of tauopathies is the abnormal aggregation and subsequent propagation of tau fibrils. Therapeutic intervention in this aggregation process is one of several options to attenuate or halt pathological development. To test new approaches, well characterized rodent models are a useful tool. Therefore, oligomerization and aggregation of tau was characterized in a transgenic mouse line expressing mutant tau. Using Western Blots, mass spectrometry (MS), homogenous time-resolved fluorescence (HTRF) and immunohistochemistry, different brain regions were analyzed over 9 months. Spontaneous locomotor activity was performed in parallel to investigate a potential influence of tau aggregates on behavior. Tau oligomerization and aggregation was evaluated in WT and P301S (B6:C3-Tg(Prnp-MAPT*P301S)PS19Vle/J) transgenic mice at 3, 6 and 9 months in the cortex, hippocampus and spinal cord. Proteins from homogenates of the different brain structures were separated using semi-native polyacrylamide gel electrophoresis. The different soluble tau oligomers were revealed on nitrocellulose blots using the tau antibody K9JA (DAKO). For MS, gel bands were excised, trypsin digested and peptides analyzed in LC-SRM mode using a triple quadrupole instrument. Presence of tau aggregates in the 3 structures was confirmed using HTRF (Cisbio). Tau phosphorylation and conformation was characterized using the antibodies AT8 and MC1, respectively. Spontaneous locomotor activity was evaluated over 90 min with 10-min recording interval. Using the PS19 strain of tau transgenic mice, a time-dependent decrease of tau monomers with a corresponding increase in tau oligomers was observed in the cortex. A similar observation was made for the hippocampus. This time-dependent increase in tau oligomer formation was confirmed in the cortex and the hippocampus using HTRF. In both structures, tau aggregates start to increase at 6 months and show significantly higher amounts at 9 months. Tau aggregates are less prominent in the spinal cord. Phospho-tau is clearly present at 9 months in all structures investigated, whereas the conformational antibody only slightly stained these regions. We observed no change in locomotor activity in this tau mutant strain at the ages tested. The PS19 tau mouse model shows progressive tau pathology in hippocampal and cortical structures and represents a useful model for drug discovery.