Biology subjects

Grutzendler, J.

Publications and source records attributed to Grutzendler, J..

7 recordsLinked to original sources

bioRxiv2026

Programming Brain Cell-Type-Selective Delivery In Vivo with Transporter-Guided Therapeutics

Many diseases arise from dysfunction of defined cell populations, yet most therapeutics distribute broadly, limiting efficacy and causing toxicity. We developed ExACT, a platform for cell-type-selective intracellular delivery that exploits membrane transporters. In vivo screening of combinatorial fluorescent small-molecule libraries in mouse brain identified chemistries whose uptake is dictated by endogenous transporter expression, yielding compounds with preferential entry into neurons, astrocytes, pericytes and endothelial cells. One series showed strong selectivity for brain and retinal endothelium, where Slco1a4 mediated uptake. This selectivity principle extended to the human orthologue SLCO1A2, highly expressed in brain endothelium and oligodendrocytes, where it mediated selective uptake in a humanized mouse model and human iPSC-derived oligodendrocytes. Ectopic expression of SLCO1A2 in neurons via gene therapy created a synthetic entry port, conferring ExACT conjugate uptake on otherwise inaccessible cells. Bifunctional compounds linking transporter-targeting motifs to antisense oligonucleotides or small-molecule drugs retained pharmacological activity while conferring transporter-dependent cell-type selectivity, illustrating how transporter diversity can be harnessed for precision pharmacotherapy.

bioengineering↗

bioRxiv2023

TREM2 and APOE do not modulate phagocytic clearance of dying cells in the live mammalian brain

TREM2 and APOE are two major risk factors for Alzheimers disease (AD) that have been proposed to play crucial roles in microglia pathophysiology by affecting their ability to phagocytose cellular debris or aggregated proteins. In this study, we investigated for the first time the impact of TREM2 and APOE on the removal of dying neurons in the live brain by implementing a targeted photochemical method for programmed cell death induction combined with high-resolution two-photon imaging. Our findings showed that the deletion of either TREM2 or APOE did not affect the dynamics of microglia engagement with dying neurons or their efficiency in phagocytosing corpses. Interestingly, while microglia that encapsulate amyloid deposits were capable of phagocytosing dying cells without disengaging from plaques or moving their cell bodies; in the absence of TREM2, microglia cell bodies were observed to readily migrate towards dying cells, further disengaging from plaques. Our data suggest that TREM2 and APOE variants are unlikely to increase risk of AD through impaired corpse phagocytosis. SummaryHigh-resolution two-photon imaging of programmed cell death in the live mouse brain reveals that neither TREM2 nor APOE modulate microglia phagocytosis of neuronal corpses. However, TREM2 regulates microglia migratory behavior towards dying cells in the vicinity of amyloid plaques.

neuroscience↗

bioRxiv2022

Spatial proteomics and iPSC modeling uncover mechanisms of axonal pathology in Alzheimer's disease

Axonal spheroids (dystrophic neurites) are commonly found around amyloid deposits in Alzheimers disease (AD). They impair electrical conduction, disrupt neural circuits, and correlate with AD severity. Despite their significance, the mechanisms underlying spheroid formation remain unknown. To address this, we developed a proximity labeling proteomics approach to uncover the proteome of spheroids in human postmortem and mouse brains. Additionally, we established a human iPSC-derived AD model allowing mechanistic investigation of spheroid pathology and optical electrophysiology. This approach revealed the subcellular molecular architecture of spheroids and identified abnormalities in key biological processes, including protein turnover, cytoskeleton dynamics, and lipid transport. Notably, the PI3K/AKT/mTOR pathway, which regulates these processes, was activated within spheroids. Furthermore, phosphorylated mTOR levels in spheroids strongly correlated with AD severity in humans. Importantly, inhibition of mTOR in iPSC-derived neurons and in mice ameliorated spheroid pathology. Altogether, our study provides a multidisciplinary toolkit for investigating mechanisms and novel targets for axonal pathology in neurodegeneration.

neuroscience↗

bioRxiv2020

Single-cell in vivo brain optogenetic stimulation by two-photon excitation fluorescence transfer

Optogenetic manipulation with single-cell resolution can be achieved by two-photon excitation; however, this frequently requires relatively high laser powers or holographic illumination. Here we developed a practical strategy to improve the efficiency of two-photon stimulation by positioning fluorescent proteins or small fluorescent molecules with high two-photon cross-sections in the vicinity of opsins. This generates a highly localized source of endogenous single-photon illumination that can be tailored to match the optimal opsin absorbance. Through neuronal and vascular stimulation in the live mouse brain, we demonstrate the utility of this technique to achieve more efficient opsin stimulation, without loss of cellular resolution. We also provide a theoretical framework for understanding the potential advantages and constrains of this methodology, with suggestions for future improvements. Altogether, this fluorescence transfer illumination method allows experiments difficult to implement in the live brain such as all-optical neural interrogation and control of regional cerebral blood flow.

neuroscience↗

bioRxiv2020

Aberrant axonal pathfinding and exuberant myelination in an inducible model of neocortical heterotopia

Neocortical heterotopia consist of ectopic neuronal clusters that are frequently found in individuals with cognitive disability and epilepsy. However, their pathogenesis remains poorly understood due in part to a lack of tractable animal models. We have developed an inducible model of focal heterotopia that enables their precise spatiotemporal control and high-resolution optical imaging in live mice. Here we report that heterotopia are associated with striking patterns of hypermyelinated and circumferentially projecting axons around neuronal clusters. Despite their aberrant axonal patterns, in vivo calcium imaging revealed that heterotopic neurons remain functionally connected to other brain regions, highlighting their potential to influence global neural networks. These aberrant patterns only form when heterotopia are induced during a critical embryonic temporal window, but not in early postnatal development. Our model provides a new way to investigate heterotopia formation in vivo and revealed features suggesting the existence of developmentally-modulated, neuron-derived axon guidance and myelination factors.

developmental biology↗

bioRxiv2019

3D super-resolution deep-tissue imaging in living mice

Stimulated emission depletion (STED) microscopy enables the three-dimensional (3D) visualization of dynamic nanoscale structures in living cells, offering unique insights into their organization. However, 3D-STED imaging deep inside biological tissue is obstructed by optical aberrations and light scattering. We present a STED system that overcomes these challenges. Through the combination of 2-photon excitation, adaptive optics, far-red emitting organic dyes, and a long-working distance water-immersion objective lens, our system achieves aberration-corrected 3D super-resolution imaging, which we demonstrate 164 {micro}m deep in fixed mouse brain tissue and 76 {micro}m deep in the brain of a living mouse.

biophysics↗

bioRxiv2018

Flexible Learning-Free Segmentation and Reconstruction for Sparse Neuronal Circuit Tracing

Imaging is a dominant strategy for data collection in neuroscience, yielding stacks of images that often scale to gigabytes of data for a single experiment. Machine learning algorithms from computer vision can serve as a pair of virtual eyes that tirelessly processes these images, automatically constructing more complete and realistic circuits. In practice, such algorithms are often too error-prone and computationally expensive to be immediately useful. We address these shortcomings with a new fast, flexible, learning-free method for sparse segmentation and reconstruction of neural volumes. Unlike learning methods, our Flexible Learning-free Reconstruction of Imaged Neural volumes (FLoRIN) pipeline exploits structure-specific contextual clues and requires no training. This approach generalizes across different modalities, including serially-sectioned scanning electron microscopy (sSEM) of genetically labeled and contrast enhanced processes, spectral confocal reflectance (SCoRe) microscopy, and high-energy synchrotron X-ray microtomography (CT) of large tissue volumes. We deploy the FLoRIN pipeline on newly published and novel mouse datasets, demonstrating the high biological fidelity of the pipelines reconstructions, which are of sufficient quality for preliminary biological study. Compared to existing supervised learning methods, it is both significantly faster (up to several orders of magnitude) and produces high-quality reconstructions that are robust to noise and artifacts.

neuroscience↗