TAU pathology dependent microtubule impairment in models of genetic tauopathy

• Applicant: Dr. Hans Zempel
• Subject Area: Molecular and Cellular Neurology and Neuropathology ; Human Genetics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 560158295

TAU is a neuronal microtubule-associated protein mislocalized and aggregated in a battery of diseases termed tauopathies, i.a. genetic forms of dementia syndromes (e.g. Alzheimer disease (AD)-like genetic forms of frontotemporal dementia (FTD)). Microtubules are essential for neuronal function, but in tauopathies neuronal microtubules are lost. In AD model systems, we showed that microtubule loss is key to AD-induced neuronal dysfunction, and is induced by Tyrosin-Tubulin-Ligase-Like (TTLL) 6. TTLLs are a class of enzymes (currently 13 known) that regulate microtubule dynamics and stability via specific post translational modifications of microtubules, of which polyglutamylation can lead to subsequent recruitment of SPASTIN and other microtubule severing enzymes. We showed that TAU-induced TTLL6-translocation and subsequent SPASTIN mediated severing leads to AD-like neuronal dysfunction. Here, we show that in FTD-derived transgenic mice, TAU missorting is associated with decreased microtubule stability. I hypothesize that in case of (FTD-associated) genetic tauopathy, a subset of TTLL(s) is responsible for TAU-mediated decreased microtubule stability, and may be a therapeutic target for genetic tauopathies and related dementia syndromes. Here, we aim to study the relationship between TAU and different TTLLs, and their role in microtubule loss in FTD-derived model systems. We aim to test the therapeutic potential of TTLL reduction in tauopathy paradigms in-vitro (human induced pluripotent stem cell- (iPSC-) derived neurons) and in-vivo (P301L-TAU-humanized mice). We will focus on iPSC-derived human neurons (established in the lab, including MAPT-KO) and will use our established (inducible & tunable) lentiviral expression system to express disease-associated TAU (with a focus on the frequent P301L mutation), with the aim to investigate the activities of TAU, SPASTIN and TTLLs in disease paradigms, and to assess effects of reducing TTLL activity. We will establish a human/humanized neuronal model system of TAU mislocalization and subsequent microtubule loss, and identify the responsible TTLL(s) mediating loss of microtububules and neuronal dysfunction. We will use our established state of the art high-/superresolution (e.g. STED-based microtubule structure) and life-imaging (calcium-imaging for neuronal function, EB3-imaging for microtubule-dynamics) expertise, but also standard immunofluorescence-microscopy (e.g. for synapse-studies) and biochemistry/molecular biology methods (e.g. for interaction and expression studies), all established in the lab. Finally, using LV/AAV-based knockdown, we will asses the therapeutic value of reducing TTLL activity in in-vitro and in-vivo (in human iPSC-derived, human disease relevant neurons, as well as in P301L-TAU-humanized mice). We explore for the first time the disease relevance of the TAU/TTLL/SPASTIN axis in genetic forms of tauopathy, hopefully opening up novel therapeutic approaches.

• DFG Programme: Research Grants