The challenge
Tauopathies, including Alzheimer’s disease and frontotemporal dementia, are defined by pathological tau aggregation, yet their underlying mechanisms remain poorly understood. A major limitation has been the absence of human-relevant models that naturally develop late-stage disease hallmarks such as tau tangles and neurodegeneration.
Conventional models – especially animal systems or iPSC-derived neurons – fail to replicate the adult human tau isoform balance, particularly the critical 3R:4R ratio. In most stem cell–derived neurons, tau expression resembles a fetal state, lacking sufficient 4R tau, which is strongly implicated in disease progression. Moreover, existing models often require artificial overexpression or external seeding of tau aggregates, limiting physiological relevance. These constraints hinder both mechanistic studies and the development of disease-modifying therapies.
Our approach
We engineered human iPSC-derived neurons to express adult-like 4R tau by genome editing the endogenous MAPT locus. We combined this with synergistic disease-associated mutations (P301L and S320F), enabling neurons to autonomously develop tau pathology without external triggers. The model was validated using molecular, imaging, and functional assays.
Our findings
The engineered neurons developed hallmark features of advanced tauopathy, including tau misfolding, hyperphosphorylation, aggregation into tangle-like structures, and formation of seeding-competent tau. These pathological processes emerged progressively over time and were strongly dependent on 4R tau expression combined with synergistic mutations.
Notably, neurons expressing exclusively mutant 4R tau exhibited dramatically increased pathology, including widespread aggregation and enhanced seeding activity. The model also showed early signs of neurodegeneration, such as synapse loss and nuclear abnormalities. Furthermore, tau pathology appeared clustered, suggesting mechanisms of interneuronal spreading. Importantly, the system proved suitable for translational applications, including testing therapeutic compounds and evaluating tau PET tracers.
The implications
This model provides a physiologically relevant human platform to study tauopathies, enabling investigation of disease mechanisms, biomarker development, and therapeutic testing in a controlled and scalable system.
Creating SyNergies
This work exemplifies interdisciplinary collaboration within the Munich research ecosystem, integrating stem cell biology, neurodegeneration research, and translational imaging. By combining expertise in molecular engineering, disease modeling, and clinical biomarker development, the teams of Dominik Paquet, Matthias Brendel, and Martina Schifferer established a platform bridging basic science and clinical application. Their joint efforts highlight how SyNergy fosters innovation across domains to accelerate progress in neurodegenerative disease research.
