Biology subjects

Götz, J.

Publications and source records attributed to Götz, J..

9 recordsLinked to original sources

bioRxiv2026

Optogenetic cochlear stimulation evokes midbrain activity with near-physiological temporal fidelity

When hearing fails, stimulation of the auditory nerve by electrical cochlear implants (eCIs) partially restores hearing, with most eCI users achieving open speech understanding. However, the broad current spread from each electrode limits frequency coding and speech understanding in daily situations with background noise. Spatially confined optogenetic stimulation by future optical cochlear implants (oCIs) improves frequency coding but millisecond closing kinetics of channelrhodopsins (ChRs) might limit temporal coding. Here, we evaluated the utility of fast-closing f-Chrimson for processing temporal information in the auditory system of Mongolian gerbils. We recorded neural activity in the inferior colliculus evoked by f-Chrimson-mediated optogenetic stimulation of the cochlea. F-Chrimson enabled energy-efficient stimulation of the auditory pathway at rates [≥]150 Hz, outperforming the slower ChR variants CatCh (blue) and ChReef (green). Energy thresholds for activation of the auditory pathway were in the low {micro}J range, between ChReef (sub-{micro}J) and CatCh. Dynamic range and frequency selectivity were comparable to previous observations with CatCh and outperformed electrical stimulation. In conclusion, employing fast-gating ChRs harnesses improved spectral coding without degrading temporal coding. The Paper Explained ProblemElectrical cochlear implants (eCIs) partially restore speech comprehension in most of 1 million otherwise severely deaf people. However, most CI-users face challenges hearing in daily situations. Spectrally more selective stimulation of the auditory nerve by optical cochlear implants (oCIs) promises to overcome this limitation. However, the closing kinetics of channelrhodopsins (ChR) limit the temporal bandwidth of bionic sound coding. Improving the ChR properties and evaluating temporal coding remain major objectives for developing hearing restoration by oCI. ResultsHere, we evaluate the utility of waveguide-based oCI using the fast-closing ChR Chrimson (f-Chrimson) for encoding of temporal, spectral and intensity information by multi-electrode-array (MEA) recordings from the midbrain. We compare f-Chrimson-mediated bionic coding to acoustic coding as well as to previous data acquired with optogenetic stimulation using other ChRs and with electrical stimulation. F-Chrimson enabled energy-efficient stimulation of the auditory pathway at rates [≥]150 Hz, outperforming the slower ChR variants CatCh (blue) and ChReef (green). Intensity and frequency coding were comparable to previous observations with CatCh and outperformed electrical stimulation. ImpactThis study demonstrates near physiological temporal coding with the fast-closing ChR f-Chrimson, indicating that improved spectral coding by oCI is not traded off by poor temporal fidelity.

neuroscience↗

bioRxiv2025

Targeting intracellular tau with a gene-encoded single-chain antibody promotes neuronal homeostasis and ameliorates tau pathology

The intraneuronal aggregation of tau is a key driver of pathogenesis in Alzheimer's disease and other tauopathies. The positively charged proline-rich region and microtubule-binding domain of tau are important for tubulin binding which enables axonal transport in physiological conditions. In disease, however, the positively charged repeat domains of such regions become exposed, facilitating tau-tau aggregation and other pathogenic tau-protein interactions which leads to neuronal dysfunction. Here, we generated a polyanionic peptide to electrostatically interact with tau and fused it to an inert single-chain variable fragment (scFv) antibody for improved peptide half-life and downstream intraneuronal expression. The resultant polyanionic peptibody, ACR12, was investigated in vitro and in tau transgenic mice for ability to prevent tau aggregation and associated disease phenotypes. In human neuroblastoma cells, ACR12 was stably expressed within the cytoplasm where it successfully engaged intracellular tau. DNA encoding ACR12 was then packaged into a brain-penetrant Adeno-associated virus, AAV-PHP.eB, for intravenous delivery into K3 tau transgenic mice. Such treatment facilitated long-term intraneuronal expression of ACR12 and reduced total and phosphorylated tau in the brain. ACR12 treatment in female K3 mice also restored deregulated neuronal proteins to wild-type levels. This study highlights the role of positively charged domains in tau pathogenesis and demonstrates the therapeutic utility of electrostatic tau interactors.

neuroscience↗

bioRxiv2025

Tau controls NMDA receptor trafficking during homeostatic synaptic plasticity

Homeostatic synaptic plasticity is essential for maintaining stable neural circuit function by preventing excessive neuronal excitation or inhibition. Chronic perturbation of neuronal activity triggers a compensatory modulation of the number of -amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) glutamate receptors at the excitatory synapses. Previous research has primarily focused on AMPA receptors, yet the molecular mechanisms regulating the trafficking of NMDA receptors during homeostatic synaptic scaling remain unclear. Here we identify the microtubule-associated protein Tau as an essential molecule that mediates the synaptic upscaling of GluN2B-containing NMDA receptors during prolonged synaptic inactivity. Chronic activity blockade increases Tau phosphorylation at Ser-235 by cyclin-dependent kinase 5 (Cdk5), enhancing its interaction with and retention of active Fyn tyrosine kinase in the postsynaptic compartment. This promotes the phosphorylation of GluN2B at Tyr-1472, subsequently stabilising the expression of NMDA receptors on the neuronal plasma membrane. Finally, we showed that Tau pathology and disease-associated mutations in Tau and the GluN2B carboxyl-terminal tail disrupt the homeostatic synaptic upscaling of NMDA receptors following chronic neuronal silencing. Together, our findings identify a physiological role for Tau in homeostatic synaptic plasticity, the perturbation of which can lead to neuronal hyperexcitation, seizures and excitotoxic cell death.

neuroscience↗

bioRxiv2025

High-resolution imaging reveals a cascade of interconnected cellular bioeffects differentiating the long-term fates of sonoporated cells

Low-intensity ultrasound combined with microbubbles is a promising, non-invasive treatment strategy for enhancing vascular permeability and targeted intracellular drug or gene delivery. After ultrasound insonification, cells can undergo reversible sonoporation, involving adaptation and recovery, or irreversible sonoporation, marked by a loss of cell viability. To design effective sonoporation-based therapeutic delivery strategies, it is therefore critical to identify the biological responses that determine these distinct cell fates. Here, we developed a custom-built high-resolution multicolour imaging device and applied a single pulse of ultrasound (267 kHz frequency, 20 s duration, and [~]110 kPa peak-negative pressure) to trigger targeted microbubble-mediated reversible and irreversible sonoporation events within a confluent monolayer of cultured Madin-Darby canine kidney (MDCK) II cells. We found that intracellular calcium levels rose rapidly and peaked within 10 s in both types of sonoporated cells, although the levels declined differently. In reversibly sonoporated cells, these levels gradually returned to baseline, whereas in irreversibly sonoporated cells, they dropped rapidly, falling well below baseline within 7.9 {+/-} 3.0 min (mean {+/-} s.d.). Using single-vesicle imaging, we further found that vesicles containing the tight junction protein claudin-5 remained mobile with subtly reduced movement in reversibly sonoporated cells, whereas they almost stalled in irreversibly sonoporated cells. The underlying microtubule network was partially disrupted in the reversibly sonoporated cells, recovering fully within 3.2 {+/-} 2.9 min (mean {+/-} s.d.). In contrast, in irreversibly sonoporated cells, the entire microtubule network collapsed within 4.0 {+/-} 2.4 min (mean {+/-} s.d.). Whilst in reversibly sonoporated cells, the uptake of the model drug propidium iodide was mild-to-moderate, without drastic cell size changes up to about 1 h post-sonication, irreversibly sonoporated cells presented with substantially higher propidium iodide uptake and shrunk completely within 43.2 {+/-} 10.5 min (mean {+/-} s.d.). Together, our study identified distinct spatiotemporal sequences of interconnected biological responses underlying different fates of sonoporated cells, providing a framework for identifying processes that could be manipulated for safe and effective sonoporation-based drug delivery.

pharmacology and toxicology↗

bioRxiv2023

Increased tau expression in the APOE4 blood-brain barrier model is associated with reduced anti-tau therapeutic antibody delivery in vitro.

Tau protein is a critical driver of neurodegeneration and an important drug target in Alzheimers disease (AD). Tau-specific immunotherapy has emerged as a promising treatment strategy for AD, however the therapeutic efficacy of anti-tau antibodies may be limited by their insufficient delivery across the blood-brain barrier (BBB). The apolipoprotein E4 allele (APOE4) is the strongest genetic risk factor for sporadic AD and is known to influence tau-mediated neurodegeneration. Interestingly, both tau and APOE4 have been implicated in the cerebrovascular pathology observed in AD. Yet, the crosstalk between APOE4 and tau at the level of the BBB and its consequences for anti-tau immunotherapeutics delivery, remain poorly understood. Here, we utilised APOE3- and APOE4-carrying human iPSC-derived induced brain endothelial-like cells (iBECs) as a sporadic AD BBB model, determined the levels of endogenous tau in iBECs, and explored the transport of two novel monoclonal anti-tau antibodies, RNF5 and RN2N, across the in vitro barrier. Our results demonstrate that MAPT gene transcription, tau protein levels and tau phosphorylation are increased in iBECs in an APOE4-related manner and are associated with reduced iBEC monolayer integrity and increased permeability to biologically inert fluorescent tracers. Additionally, elevated levels of intracellular tau in APOE4 cells were accompanied by the reduced passive permeability of therapeutic anti-tau antibodies through the APOE4 iBEC monolayer, which could be improved by the application of focused ultrasound and microbubble drug-delivery technology. Together, our study illustrates a new role for APOE4 and tau in human iBECs with potential implications for BBB dysfunction and anti-tau therapeutic antibody delivery.

cell biology↗

bioRxiv2022

Single-molecule imaging reveals Tau trapping at nanometer-sized dynamic hot spots near the plasma membrane

Accumulation of Tau aggregates is a pathological hallmark of Alzheimers disease, but little is known about where these aggregates assemble and how stable these assemblies are. Using quantitative, single-molecule imaging, we show that Tau exhibits spatial and kinetic heterogeneity near the plasma membrane, resulting in the formation of nanometer-sized hot spots smaller than the diffraction limit. The hot spots lasted tens of seconds, much longer than the short dwell time (~40 ms) of Tau on microtubules. Pharmacological and biochemical disruption of Tau/microtubule interactions did not affect hot spot formation, suggesting that these are different from the reported Tau condensation on microtubules. Although cholesterol removal has been shown to reduce Tau pathology, its depletion did not affect Tau hot spot dynamics. Our study identifies an intrinsic dynamic property of Tau near the plasma membrane that may facilitate the formation of assembly sites for Tau to assume its physiological and pathological functions.

neuroscience↗

bioRxiv2021

Claudin-5 binder enhances focused ultrasound-mediated opening in an in vitro blood-brain barrier model

RationaleThe blood-brain barrier (BBB) while functioning as a gatekeeper of the brain, impedes cerebral drug delivery. An emerging technology to overcome this limitation is focused ultrasound (FUS). When FUS interacts with intravenously injected microbubbles (FUS+MB), the BBB opens, transiently allowing the access of therapeutic agents into the brain. However, the ultrasound parameters need to be tightly tuned: when the acoustic pressure is too low there is no opening, and when it is too high, bleeds can occur. We therefore asked whether BBB permeability can be increased by combining FUS+MB with a second modality such that in a clinical setting lower acoustic pressures could be potentially used. MethodsGiven that FUS achieves BBB opening by the disruption of tight junction (TJ) proteins such as claudin-5 of brain endothelial cells, we generated a stable MDCK II cell line (eGFP-hCldn5-MDCK II) that expresses fluorescently tagged human claudin-5. Two claudin-5 binders, mC5C2 (a peptide) and cCPEm (a truncated form of an enterotoxin), that have been reported previously to weaken the barrier, were synthesized and assessed for their abilities to enhance the permeability of cellular monolayers. We then performed a comparative analysis of single and combination treatments. ResultsWe successfully generated a novel cell line that formed functional monolayers as validated by an increased transendothelial electrical resistance (TEER) reading and a low (< 0.2%) permeability to sodium fluorescein (376 Da). We found that the binders exerted a time- and concentration-dependent effect on BBB opening when incubated over an extended period, whereas FUS+MB caused a rapid barrier opening followed by recovery after 12 hours within the tested pressure range. Importantly, preincubation with cCPEm prior to FUS+MB treatment resulted in greater barrier opening compared to either FUS+MB or cCPEm alone as measured by reduced TEER values and an increased permeability to fluorescently labelled 40 kDa dextran (FD40). ConclusionThe data suggest that pre-incubation with clinically suitable binders to TJ proteins may be a general strategy to facilitate safer and more effective ultrasound-mediated BBB opening in cellular and animal systems and potentially also for the treatment of human diseases of the brain.

neuroscience↗

bioRxiv2021

A comparative study of the effects of Aducanumab and scanning ultrasound on amyloid plaques and behavior in the APP23 mouse model of Alzheimer disease

BackgroundAducanumab is an anti-amyloid-{beta} (A{beta}) antibody that achieved reduced amyloid pathology in Alzheimers disease (AD) trials, but it is controversial whether it also improved cognition. It has been claimed that this would require a sufficiently high cumulative dose of the antibody in the brain. Therapeutic ultrasound, in contrast, has only begun to be investigated in human AD clinical trials. We have previously shown that scanning ultrasound in combination with intravenously injected microbubbles (SUS), that temporarily and safely opens the blood-brain barrier (BBB), removes amyloid and restores cognition in APP23 mice. It has not been directly tested how the effects of SUS compare to immunotherapy or whether a combination therapy is more effective. MethodsIn a study comprising four treatment arms, we tested the efficacy of an Aducanumab analogue, Adu, in comparison to SUS, as well as a combination therapy in APP23 mice, using sham as a control (aged 13-22 months). The active place avoidance (APA) test was used to test spatial memory, and histology and ELISA were used to measure amyloid. Brain antibody levels were also determined. ResultsWe found that both Adu and SUS reduced the total plaque area in the hippocampus to a similar degree, with no additive effect in the combination treatment (SUS+Adu). Whereas there was only a trend towards a reduction for both Adu and SUS in the cortex, the combination trial yielded a statistically significant reduction compared to sham. Only the SUS and SUS+Adu groups included animals that had their plaque load reduced to below 1% from above 10%. There was a robust improvement in spatial memory for SUS+Adu only. In this group, when measured three days post-treatment, Adu levels were still 5-fold increased in the combination therapy compared to delivery of Adu on its own. Together, these findings suggest that SUS should be seriously considered as a treatment option for AD. Alternatively, a combination trial using Aducanumab together with ultrasound to increase brain levels of Aducanumab may be warranted, as the two approaches may engage different (albeit shared) clearance mechanisms.

neuroscience↗

bioRxiv2020

Frontotemporal dementia mutant tau (P301L) locks Fyn in an open, active conformation conducive to nanoclustering

Fyn is a Src kinase that controls critical signalling cascades and its postsynaptic enrichment underpins synaptotoxicity in Alzheimers disease (AD) and frontotemporal dementia (FTLD-tau). Previously, we found that pathogenic FTLD tau mutant (P301L) expression promotes aberrant trapping of Fyn in nanoclusters within hippocampal dendrites via an unknown mechanism (Padmanabhan et al., 2019). Here, we imaged Fyn-mEos2 using single particle tracking photoactivated localization microscopy (sptPALM) to demonstrate that nanoclustering of Fyn in hippocampal dendrites is promoted by Fyns open, primed conformation. Disrupting the auto-inhibitory, closed conformation of Fyn through phospho-inhibition, and perturbation of Fyns SH3 domain increases, Fyns nanoscale trapping. However, inhibition of Fyns catalytic domain has no impact on its mobility. Tau-P301L promotes Fyn lateral trapping via Fyn opening and ensuing increased catalytic activation. Pathogenic tau may therefore drive synaptotoxicity by locking Fyn in an open, catalytically active conformation, leading to postsynaptic entrapment and aberrant signalling cascades.

neuroscience↗