Sonia Koyama — Tauopathy Researcher

Sonia Koyama, PhD — Tauopathy Researcher

Dr. Sonia Koyama is a researcher at the [Tokyo Metropolitan Institute of Gerontology](/institutions/tokyo-metropolitan) (TMIG), a premier Japanese research institution dedicated to understanding the biology of aging and neurodegenerative diseases. Her research focuses on the molecular mechanisms of tau aggregation and propagation in 4R-tauopathies, with particular emphasis on post-translational modifications, tau strain diversity, and the development of cellular and iPSC models of PSP and corticobasal degeneration (CBD).

Research Focus

Sonia Koyama, PhD — Tauopathy Researcher

Dr. Sonia Koyama is a researcher at the [Tokyo Metropolitan Institute of Gerontology](/institutions/tokyo-metropolitan) (TMIG), a premier Japanese research institution dedicated to understanding the biology of aging and neurodegenerative diseases. Her research focuses on the molecular mechanisms of tau aggregation and propagation in 4R-tauopathies, with particular emphasis on post-translational modifications, tau strain diversity, and the development of cellular and iPSC models of PSP and corticobasal degeneration (CBD).

Research Focus

Tau Aggregation Mechanisms

Dr. Koyama's work has established a comprehensive understanding of how 4R-tau forms the pathological aggregates that define PSP and CBD:

• Aggregation kinetics: Studies have characterized the nucleation, elongation, and branching phases of 4R-tau filament formation, identifying critical kinetic parameters that distinguish PSP from AD tau aggregation[@koyama2024aggregation]
• Post-translational modifications (PTMs): Comprehensive mapping of tau PTMs in PSP brain tissue has revealed that specific patterns of phosphorylation, acetylation, and truncation characterize 4R-tau pathology. The 2020 study established that acetylation at Lys280 blocks proteolytic cleavage and stabilizes toxic tau conformers[@koyama2020ptm]
• Co-factors and seeding: Research has identified that polyamines, metals (Zn2+, Cu2+), and RNA molecules accelerate 4R-tau nucleation, providing mechanistic insight into the self-replicating nature of tau pathology[@koyama2015prion]

iPSC Models of 4R Tauopathies

Dr. Koyama pioneered the development of patient-derived iPSC models for PSP and CBD:

• TMIG cohort: The 2016 derivation paper established protocols for generating neurons and glia from PSP patients carrying MAPT mutations (P301S, IVS5+10) and sporadic cases. These neurons recapitulate key features: 4R-tau accumulation, reduced mitochondrial function, and increased susceptibility to oxidative stress[@koyama2016stem]
• 2024 breakthrough: A landmark study using TMIG iPSC models identified genetic and chemical modifiers of tau propagation, screening 3,000+ compounds for tau propagation inhibitors and identifying HDAC6 as a high-value target[@koyama2024stem]
• 2025 extension: Single-cell transcriptomics of iPSC-derived neurons revealed cell-type-specific vulnerability patterns — certain neuronal subtypes accumulate tau faster and show earlier transcriptional dysregulation, providing a cellular substrate for understanding PSP clinical heterogeneity[@koyama2025single]

Tau Propagation and Spreading

A central theme of Dr. Koyama's research is understanding how tau pathology spreads through neural circuits:

• Cell-to-cell transmission: Using microfluidic chambers and co-culture systems, her lab has characterized the mechanisms of tau release (synaptic vesicles, exosomes, free diffusion) and uptake (LDLR-family receptors, macropinocytosis)[@koyama2019cellular]
• Vulnerability factors: Studies have identified that synaptic activity, neuronal activity state, and glial cells all modulate the efficiency of interneuronal tau transfer[@koyama2024propagation]
• Prion-like properties: Early work established the seeded nature of PSP tau aggregates — patient-derived tau fibrils efficiently templated the conversion of wild-type tau into pathological conformations in cellular and animal models[@koyama2015prion]

Tau Strain Diversity

Dr. Koyama has been at the forefront of characterizing distinct tau strains in different 4R-tauopathies:

• 2025 strain study: Using cryo-EM and biochemical profiling, her group demonstrated that PSP and CBD produce structurally distinct tau filament conformations that maintain their identity upon serial passage — analogous to prion strains. These strain differences explain the distinct clinical-pathological phenotypes[@koyama2025strain]
• Diagnostic implications: The strain concept has practical applications — seed amplification assays (RT-QuIC, PMCA) show differential detection efficiency for PSP vs CBD seeds, suggesting that assay optimization for specific strains could improve diagnostic accuracy[@koyama2021seeding]

Oligodendrocyte Tau Pathology

An underappreciated aspect of PSP is the prominent oligodendroglial tau pathology. Dr. Koyama's work has illuminated this:

• 4R-tau in oligodendrocytes: Oligodendrocytes in PSP accumulate 4R-tau in globular inclusions (often called "coiled bodies"), and her work has characterized the cellular mechanisms — including MBP phosphorylation changes, myelin lipid composition shifts, and transport deficits[@koyama2023oligodendrocyte]
• Contribution to disease: Studies suggest that oligodendrocyte tau pathology contributes to white matter damage, demyelination, and axonal degeneration in PSP, independent of neuronal tau burden
• Therapeutic targeting: Since oligodendrocytes are post-mitotic and difficult to target with small molecules, her work has explored gene therapy approaches and remyelination-promoting strategies

Biomarker Development

Dr. Koyama contributes to both fluid and imaging biomarker research:

• Tau PET correlations: A 2024 clinicopathological study correlated ante-mortem tau PET (MK-6240) binding with postmortem tau burden, validating the specificity of tau PET for 4R-tauopathies and identifying regional SUVR thresholds for diagnostic use[@koyama2024imaging]
• Fluid biomarkers: Comparative studies of CSF and plasma tau forms (total tau, p-tau181, p-tau217, p-tau231) have established that each marker provides complementary information — p-tau231 being most specific for PSP, while NfL tracks progression[@koyama2023fluid]
• PTM-based biomarkers: Her PTM mapping work has informed the development of assay-agnostic ELISA platforms that detect specific tau modifications as disease state markers

MRI-Tau Correlations

Imaging-pathology correlations have been a consistent thread in her work:

• Regional specificity: MRI cortical thinning patterns in PSP correlate with regional tau burden in a topographically specific manner — midbrain atrophy predicts substantia nigra tau load, cerebellar dentate nucleus atrophy predicts oligodendroglial tau[@koyama2022mri]
• Subtype associations: Different PSP clinical variants show distinct atrophy patterns that reflect the preferential involvement of specific neuronal populations and circuits[@koyama2022isoform]

Advanced Glycation and Metabolism

Early in her career, Dr. Koyama investigated the intersection of metabolic dysfunction and tau pathology:

• AGEs in PSP: Advanced glycation end products (AGEs) accumulate in PSP tau inclusions, suggesting that metabolic dysfunction contributes to tau aggregation kinetics through cross-linking and oxidative stress[@koyama2016glycation]
• Mitochondrial dysfunction: Studies have shown that PSP neurons exhibit reduced mitochondrial mass, altered dynamics (fission/fusion imbalance), and impaired respiration — creating a feedforward loop where tau pathology drives mitochondrial damage, which accelerates tau aggregation

Institutional Context

The [Tokyo Metropolitan Institute of Gerontology](/institutions/tokyo-metropolitan) (TMIG) is one of Japan's leading research centers on aging and neurodegeneration. Dr. Koyama's work at TMIG benefits from:

• State-of-the-art iPSC facility for generating patient-derived cell lines
• Collaboration with the Tokyo Metropolitan Neurological Hospital for clinical sample access
• Linkage to the Japanese Brain Bank Network (Japan Brain Bank Consortium)
• Access to tau PET imaging through partnerships with Japanese university hospitals
• International collaborations with groups in the US (UCSF, Mayo Clinic), Europe (UCL, University of Munich), and Asia-Pacific

Key Collaborations

• MAPT genetics group: Ongoing work on MAPT mutation carriers from Japanese cohorts, linking genotype to molecular phenotype
• Tau PET consortium: Multi-site study validating tau PET in 4R tauopathies across Asian populations
• iPSC neuroscreening: Collaboration with RIKEN BSI on high-content compound screening
• Prion research community: Interactions with prion biologists informing tau strain characterization

Cross-Links

• [Progressive Supranuclear Palsy](/diseases/progressive-supranuclear-palsy) — Primary disease focus
• [Corticobasal Degeneration](/diseases/corticobasal-degeneration) — Related 4R-tauopathy
• [4R-Tauopathies](/diseases/4r-tauopathies) — Disease category
• [Tau Protein](/proteins/tau) — Primary molecular target
• [Tau Phosphorylation Pathway](/mechanisms/tau-phosphorylation-pathway) — Key PTM mechanism
• [Tau Seed Amplification Assays](/biomarkers/tau-seed-amplification-assays) — Diagnostic assay development
• [iPSC Neuronal Models](/experiments/nhp-validation-animal-model) — Cellular model context
• [HDAC6](/entities/hdac-enzymes) — Therapeutic target from her compound screen
• [MAPT Gene](/genes/mapt) — Tau-encoding gene, MAPT mutation carriers in her cohort

Selected Publications