Biochemical Evidence for a Pathological Variant of Progressive Supranuclear Palsy

Abstract Background Tau proteins aggregate into spatially and morphologically distinct lesions in primary and secondary tauopathies. These signature lesions result from deposition of tau proteins that are distinctly modified via missense mutation and/or post‐translational modification for each disease strain. Identifying the unique tau protein abnormalities that lead to specific neurodegenerative diseases is beneficial in their early diagnosis and treatment. This is especially true for Progressive Supranuclear Palsy a primary tauopathy with clinical symptoms mirroring Parkinsonian syndromes and frontotemporal dementias. Method Biochemical analysis of tau aggregates from patients with a pathological diagnosis of Progressive Supranuclear Palsy (n = 60) demonstrate that the tau protein modifications observed in this disease result from tau that is specifically modified and thereby forms the basis of the distinct disease strains observed. Here data collected using the sarkosyl‐insoluble tau fractions from tissue samples of pathologically diagnosed patients with Progressive Supranuclear Palsy without comorbidities allows for the direct observation of the modifications. Most interesting is the variability of the tau proteins that actually accumulate for this disease opening up the possibility that tau strains may exist within any given tauopathy even as the clinical manifestations appear similar. This indicates that early and specific identification and detection of these strains is critical for the development of therapies for these diseases. Result Extraction and examination of sarkosyl‐insoluble tau proteins from deceased patients pathologically diagnosed with Progressive Supranuclear Palsy indicate that multiple tau strains exist within this primary tauopathy. Western blotting of these extracts from patient tissues demonstrates a unique banding pattern of insoluble tau in a subset of the cases that exhibit extreme hyperphosphorylation as indicated by additional high molecular weight tau banding. These patients also had an earlier age of onset and age of death indicating a more aggressive disease strain. Additional data is presented comparing the structure and seeding capability of this insoluble tau and the distribution and burden of insoluble tau in these Progressive Supranuclear Palsy patients compared to those with typical onset and insoluble tau signature. Conclusion Multiple pathological tau strains exist in Progressive Supranuclear Palsy.