Biology subjects

Glynn, C.

Publications and source records attributed to Glynn, C..

12 recordsLinked to original sources

bioRxiv2026

Femtosecond pulsed laser ablation for in-tissue electron cryo-tomography

In situ electron cryo-tomography (cryo-ET) is a powerful tool for visualising biology inside cells at the molecular scale. The routine application of cryo-ET in tissue samples promises biological insight beyond single cells, but is currently limited by the technical challenge of preparing high quality, electron-transparent specimens from thick (>100 m) biopsies efficiently. Here, we demonstrate that cryogenic femtosecond pulsed laser ablation (cryo-fs-PLA) can accelerate the preparation of vitreous specimens of mammalian brain tissue for cryo-ET. Using cryogenic fluorescence microscopy, regions of interest within high-pressure frozen tissue can be specifically targeted, and cryo-fs-PLA can be employed as a preparative step for serial cryogenic lift-out experiments. We define cryo-fs-PLA parameters and determine ablation rates for two different laser wavelengths, and demonstrate that tilt series collected on lamellae fabricated from sites exposed to cryo-fs-PLA largely maintain their vitrification state. Incorporating cryo-fs-PLA into existing cryo-ET workflows has the potential to unlock the sample preparation of tissues at the throughput necessary for routine in situ cell biology of multicellular samples.

biochemistry↗

bioRxiv2026

From wag to affect: Tail kinematic signatures of canine emotional states in computer-controlled environments

From facial expressions to gestures, animals use multiple signal modalities to express emotions and communicate. In dogs, tail movements are conspicuous behaviours associated with emotional states, but this link remains debated. We investigated canine emotional states underlying tail wagging by systematically analysing differences in tail movements in a computer-controlled task encompassing two non-social Conditions - Rewarded (positive) and Unrewarded (negative), and two Epochs (pre-response and outcome anticipation). Using pose-tracking we found that 11 out of 23 dogs did not wag their tails in at least 75% of trials, suggesting that some dogs may inherently wag less or that tail wagging is primarily a social signal. Our results showed that dogs were more likely to wag during positive anticipation; whereas in the negative condition, despite tail amplitude being more prominent, increased speeds reflected arousal rather than valence. Further work should assess tail kinematics in social contexts to test and extend these findings.

animal behavior and cognition↗

bioRxiv2025

Mapping cellular targets of covalent cancer drugs in the entire mammalian body

As our understanding of biological systems reaches single-cell and high spatial resolutions, it becomes imperative that pharmacological approaches match this precision to understand drug actions. This need is particularly urgent for the targeted covalent inhibitors that are currently re-entering the stage for cancer treatments. By leveraging the unique kinetics of click reactions, we developed volumetric clearing-assisted tissue click chemistry (vCATCH) to enable deep and homogeneous click labeling across the 3D mammalian body. With simple and passive incubation steps, vCATCH offers cellular resolution drug imaging in the entire adult mouse. We combined vCATCH with HYBRiD imaging and virtual reality to visualize and quantify in vivo targets of two clinical cancer drugs, afatinib and ibrutinib, which recapitulated their known pharmacological distribution and revealed previously unreported tissue and cell type engagement potentially linked to off-target effects. vCATCH provides a body-wide, unbiased platform to map covalent drug engagements at unprecedented scale and precision.

pharmacology and toxicology↗

bioRxiv2024

Charting the molecular landscape of neuronal organisation within the hippocampus using cryo electron tomography

Cellular cryo-electron tomography (cryoET) enables the capture of detailed structural information within a biologically relevant environment. However, information in more complex samples, such as tissues, is lacking. Importantly, these observations need to be set in context of populations; imaging on the molecular scale to-date is limited to few observations in-situ that struggle to be generalised. This is due to limitations in throughput and versatility employed by current instrumentation. Here, we utilise plasma focused ion beam milling to examine the molecular landscape of mouse hippocampus by cryoET in targeted regions across multiple individuals revealing the complex organisation of macromolecules from the CA1 strata pyramidale (sp) to radiatum (sr). Our data represent a molecular atlas, producing snapshots of hippocampal architecture in adult mouse. The combination of instrumentation and application of technical advancements provides a framework to explore specific structural questions within native tissues in a targeted manner.

biochemistry↗

bioRxiv2024

Reduction of SEM charging artefacts in native cryogenic biological samples.

Scanning electron microscopy (SEM) of frozen-hydrated biological samples allows imaging of subcellular structures at the mesoscale in their native state. Combined with focused ion beam milling (FIB), serial FIB/SEM can be used to build a 3-dimensional picture of cells and tissues. The correlation of specific regions of interest with cryo-electron microscopy (cryoEM) can additionally enable subsequent high-resolution analysis. However, the adoption of serial FIB/SEM imaging-based methods is limited due to artefacts arising from insulating areas of cryogenically preserved samples. Here, we demonstrate the use of interleaved scanning to reduce charging artefacts, allowing the observation of biological features that otherwise would be masked or perturbed. We apply our method to samples where inherent features are not visible. These examples include membrane contact sites within mammalian cells, visualisation of the degradation compartment in the algae E.gracilis and observation of a network of membranes within different types of axons in an adult mouse cortex. We further propose an alternative scanning method that could also be widely applicable to imaging any non-conductive.

cell biology↗

bioRxiv2024

Biologically Driven In Vivo Occlusion Design Provides a Reliable Experimental Glaucoma Model

Fluid transport through the trabecular meshwork is a major regulator of intraocular pressure in healthy and glaucomatous eyes. Existing microbead occlusion models enable in vivo study of pressure-related glaucomatous pathology, but their long-term reliability is limited by inadequate bead-tissue interface design. Inspired by the graded porous architecture and fluid-transport function of the trabecular meshwork, we develop an injectable Viscobeads platform for sustained modulation of aqueous humor outflow. These composite microbeads integrate a non-degradable polystyrene core for structural support with a biodegradable poly(lactic-co-glycolic acid) viscoelastic shell that improves mechanical adaptation to heterogeneous trabecular meshwork fenestrations. This biologically informed design enhances outflow obstruction and enables stable IOP elevation for at least 8 weeks after a single injection. In mice, Viscobeads induce sustained ocular hypertension (average 21.4 mm Hg) and lead to a 34% loss of retinal ganglion cells by day 56. Pattern electroretinogram and flash visual evoked potential measurements further reveal early retinal ganglion cell dysfunction followed by later visual pathway impairment. Beyond disease induction, this platform supports in vivo gene screening for retinal ganglion cell survival and identifies altered sleep behavior during glaucoma progression. This work establishes a materials-driven strategy for chronic ocular hypertension modeling and therapeutic evaluation.

biophysics↗

bioRxiv2023

Tau seeding and spreading in vivo is supported by both fibrillar and oligomeric tau

Insoluble fibrillar tau, the primary constituent of neurofibrillary tangles, has traditionally been thought to be the biologically active, toxic form of tau mediating neurodegeneration in Alzheimers disease. More recent studies have implicated soluble oligomeric tau species, referred to as high molecular weight (HMW) due to its properties on size exclusion chromatography, in tau propagation across neural systems. These two forms of tau have never been directly compared. We prepared sarkosyl insoluble and HMW tau from the frontal cortex of Alzheimer patients and compared their properties using a variety of biophysical and bioactivity assays. Sarkosyl insoluble fibrillar tau is comprised of abundant paired helical filaments (PHF) as quantified by electron microscopy (EM), and is more resistant to proteinase K, compared to HMW tau which is mostly in an oligomeric form. Sarkosyl insoluble and HMW tau are nearly equivalent in potency in a HEK cell bioactivity assay for seeding aggregates and their injection reveals similar local uptake into hippocampal neurons in PS19 Tau transgenic mice. However, the HMW preparation appears to be far more potent in inducing a glial response including Clec7a-positive rod-microglia in the absence of neurodegeneration or synapse loss and promotes more rapid propagation of misfolded tau to distal, anatomically connected regions, such as entorhinal and perirhinal cortices. These data suggest that soluble HMW tau has similar properties to fibrillar sarkosyl insoluble tau with regard to tau seeding potential but may be equal or even more bioactive with respect to propagation across neural systems and activation of glial responses, both relevant tau-related Alzheimer phenotypes.

neuroscience↗

bioRxiv2021

Fragment-based ab initio phasing of peptidic nanocrystals by MicroED

Microcrystal electron diffraction (MicroED) is transforming the visualization of molecules from nanocrystals, rendering their three-dimensional atomic structures from previously unamenable samples. Peptidic structures determined by MicroED include naturally occurring peptides, synthetic protein fragments and peptide-based natural products. However, as a diffraction method, MicroED is beholden to the phase problem, and its de novo determination of structures remains a challenge. ARCIMBOLDO, an automated, fragment-based approach to structure determination. It eliminates the need for atomic resolution, instead enforcing stereochemical constraints through libraries of small model fragments, and discerning congruent motifs in solution space to ensure validation. This approach expands the reach of MicroED to presently inaccessible peptidic structures including segments of human amyloids, and yeast and mammalian prions, and portends a more general phasing solution while limiting model bias for a wider set of chemical structures.

biochemistry↗

bioRxiv2018

Homochiral and racemic MicroED structures of a peptide from the ice nucleation protein InaZ

The ice nucleation protein InaZ of Pseudomonas syringae contains a large number of degenerate repeats that span more than a quarter of its sequence and include the segment GSTSTA. We determine ab initio structures of this repeat segment, resolved to 1.1[A] by microfocus x-ray crystallography and 0.9[A] by the cryoEM method MicroED, from both racemic and homochiral crystals. We evaluate the benefits of racemic protein crystals for structure determination by MicroED and confirm that phase restriction introduced by crystal centrosymmetry increases the number of successful trials during ab initio phasing of electron diffraction data. Both homochiral and racemic GSTSTA form amyloid-like protofibrils with labile, corrugated antiparallel beta sheets that mate face to back. The racemic GSTSTA protofibril represents a new class of amyloid assembly in which all left-handed sheets mate with their all right-handed counterparts. Our determination of racemic amyloid assemblies by MicroED reveals complex amyloid architectures and illustrates the racemic advantage in macromolecular crystallography, now with sub-micron sized crystals.\n\nSynopsisThe atomic asymmetry, left or right handedness, present in macromolecules and first described by Pasteur in his experiments with tartaric acid, is evident even in complex molecular assemblies like amyloid fibrils. Here, using the cryoEM method MicroED, we show that a segment from the ice nucleation protein InaZ assembles into homochiral and racemic water-binding amyloid protofibrils.

biochemistry↗

bioRxiv2018

Analysis of global and site-specific radiation damage in cryo-EM

Micro-crystal electron diffraction (MicroED) is an emerging method in cryo-EM for structure determination using nanocrystals. It has been used to solve structures of a diverse set of biomolecules and materials, in some cases to sub-atomic resolution. However, little is known about the damaging effects of the electron beam on samples during such measurements. We assess global and site-specific damage from electron radiation on nanocrystals of proteinase K and of a prion hepta-peptide and find that the dynamics of electron-induced damage follow well-established trends observed in X-ray crystallography. Metal ions are perturbed, disulfide bonds are broken, and acidic side chains are decarboxylated while the diffracted intensities decay exponentially with increasing exposure. A better understanding of radiation damage in MicroED improves our assessment and processing of all types of cryo-EM data.

biochemistry↗

bioRxiv2017

MicroED Structures from Micrometer Thick Protein Crystals

Theoretical calculations suggest that crystals exceeding 100 nm thickness are excluded by dynamical scattering from successful structure determination using microcrystal electron diffraction (MicroED). These calculations are at odds with experimental results where MicroED structures have been determined from significantly thicker crystals. Here we systematically evaluate the influence of thickness on the accuracy of MicroED intensities and the ability to determine structures from protein crystals one micrometer thick. To do so, we compare ab initio structures of a human prion protein segment determined from thin crystals to those determined from crystals up to one micrometer thick. We also compare molecular replacement solutions from crystals of varying thickness for a larger globular protein, proteinase K. Our results indicate that structures can be reliably determined from crystals at least an order of magnitude thicker than previously suggested by simulation, opening the possibility for an even broader range of MicroED experiments.\n\nSummaryAtomic resolution protein structures can be determined by MicroED from crystals that surpass the theoretical maximum thickness limit by an order of magnitude.

biochemistry↗

bioRxiv2017

Evidence for time division multiplexing of multiple simultaneous itemsin a sensory coding bottleneck

How the brain preserves information about multiple simultaneous items is poorly understood. We report that single neurons can represent multiple different stimuli by interleaving different signals across time. We record single units in an auditory region, the inferior colliculus, while monkeys localize 1 or 2 simultaneous sounds. During dual-sound trials, we find that some neurons fluctuate between firing rates observed for each single sound, either on a whole-trial or on a sub-trial timescale. These fluctuations are correlated in pairs of neurons, can be predicted by the state of local field potentials prior to sound onset, and, in one monkey, can predict which sound will be reported first. We find corroborating evidence of fluctuating activity patterns in a separate data set involving responses of inferotemporal cortex neurons to multiple visual stimuli. Alternation between activity patterns corresponding to each of multiple items may therefore be a general strategy to enhance the brain processing capacity, potentially linking such disparate phenomena as variable neural firing, neural oscillations, and limits in attentional/memory capacity.

neuroscience↗