4-Repeat tau seeds and templating subtypes as brain and CSF biomarkers of frontotemporal lobar degeneration

Eri Saijo, Michael A. Metrick, Shunsuke Koga, Piero Parchi, Irene Litvan, Salvatore Spina, Adam Boxer, Julio C. Rojas, Douglas Galasko, Allison Kraus, Marcello Rossi, Kathy Newell, Gianluigi Zanusso, Lea T. Grinberg, William W. Seeley, Bernardino Ghetti, Dennis W. Dickson, Byron Caughey

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


To address the need for more meaningful biomarkers of tauopathies, we have developed an ultrasensitive tau seed amplification assay (4R RT-QuIC) for the 4-repeat (4R) tau aggregates of progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and other diseases with 4R tauopathy. The assay detected seeds in 106–109-fold dilutions of 4R tauopathy brain tissue but was orders of magnitude less responsive to brain with other types of tauopathy, such as from Alzheimer’s disease cases. The analytical sensitivity for synthetic 4R tau fibrils was ~ 50 fM or 2 fg/sample. A novel dimension of this tau RT-QuIC testing was the identification of three disease-associated classes of 4R tau seeds; these classes were revealed by conformational variations in the in vitro amplified tau fibrils as detected by thioflavin T fluorescence amplitudes and FTIR spectroscopy. Tau seeds were detected in postmortem cerebrospinal fluid (CSF) from all neuropathologically confirmed PSP and CBD cases but not in controls. CSF from living subjects had weaker seeding activities; however, mean assay responses for cases clinically diagnosed as PSP and CBD/corticobasal syndrome were significantly higher than those from control cases. Altogether, 4R RT-QuIC provides a practical cell-free method of detecting and subtyping pathologic 4R tau aggregates as biomarkers.

Original languageEnglish (US)
Pages (from-to)63-77
Number of pages15
JournalActa neuropathologica
Issue number1
StatePublished - Jan 1 2020


  • Biomarker
  • Corticobasal degeneration
  • Diagnosis
  • Progressive supranuclear palsy
  • Strain
  • Tau

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Clinical Neurology
  • Cellular and Molecular Neuroscience


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