Biology subjects

Staras, K.

Publications and source records attributed to Staras, K..

6 recordsLinked to original sources

bioRxiv2021

Ultrastructural readout of in vivo synaptic activity for functional connectomics.

Large-volume ultrastructural mapping approaches yield detailed circuit wiring diagrams but lack an integrated synaptic activity readout which is essential for functional interpretation of the connectome. Here we resolve this limitation by combining functional synaptic labelling in vivo with focused ion-beam scanning electron microscopy (FIBSEM) and machine learning-based segmentation. Our approach generates high-resolution near-isotropic three-dimensional readouts of activated vesicle pools across large populations of individual synapses in a volume of tissue, opening the way for detailed functional connectomics studies. We apply this method to measure presynaptic activity in an ultrastructural context in synapses activated by sensory input in primary visual cortex in awake head-fixed mice, showing that the numbers of recycling and non-recycling vesicles approximate to a lognormal distribution across a large number of synapses. We also demonstrate that neighbouring boutons of the same axon, which share the same spiking activity, can differ greatly in their presynaptic release probability.

neuroscience↗

bioRxiv2020

Synaptic dysfunction caused by truncated tau is associated with hyperpolarization-activated cyclic nucleotide-gated channelopathy

Progressive neurodegeneration in tauopathies is mediated through an elusive mechanism. Here, we show that hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are functionally linked to disease-associated abnormalities in tau. Selective rises in the proportion of HCN-positive neurons are detected both in post-mortem human brain from Alzheimers disease and in the Tau35 mouse model of tauopathy. Tau35 mice develop progressive abnormalities including increased phosphorylated tau, enhanced HCN channel expression and decreased dendritic branching, as well as reduced synapse density that is accompanied by vesicle clustering defects. Notably, altered spine density and increased HCN channel expression in Tau35 neurons correlates with functional abnormalities in network properties, including enhanced hyperpolarization-induced membrane voltage sag and changes in the frequency and kinetics of spontaneous excitatory postsynaptic currents. Our findings are consistent with pathological changes in tauopathies impacting on HCN channels to drive network-wide structural and functional synaptic deficits, providing new targets for therapeutic intervention.

neuroscience↗

bioRxiv2019

Divergent excitation two photon microscopy for 3D random access mesoscale imaging at single cell resolution

ABSTACTIn neuroscience, diffraction limited two-photon (2P) microscopy is a cornerstone technique that permits minimally invasive optical monitoring of neuronal activity. However, most conventional 2P microscopes impose significant constraints on the size of the imaging field-of-view and the specific shape of the effective excitation volume, thus limiting the scope of biological questions that can be addressed and the information obtainable. Here, employing divergent beam optics (DBO), we present an ultra-low-cost, easily implemented and flexible solution to address these limitations, offering a several-fold expanded three-dimensional field of view that also maintains single-cell resolution. We show that this implementation increases both the space-bandwidth product and effective excitation power, and allows for straight-forward tailoring of the point-spread-function. Moreover, rapid laser-focus control via an electrically tunable lens now allows near-simultaneous imaging of remote regions separated in three dimensions and permits the bending of imaging planes to follow natural curvatures in biological structures. Crucially, our core design is readily implemented (and reversed) within a matter of hours, and fully compatible with a wide range of existing 2P customizations, making it highly suitable as a base platform for further development. We demonstrate the application of our system for imaging neuronal activity in a variety of examples in mice, zebrafish and fruit flies.

neuroscience↗

bioRxiv2019

Misfolded Amyloid β-42 induced impairment of the endo-lysosomal pathway revealed by real-time optical monitoring

Misfolding and aggregation of proteins is strongly linked to several neurodegenerative diseases but how such species bring about their cytotoxic actions remains poorly understood. Here we used specifically-designed optical reporter probes and live fluorescence imaging in primary hippocampal neurons to characterise the mechanism by which prefibrillar, oligomeric forms of the Alzheimers-associated peptide, A{beta}42, exert their detrimental effects. We used a pH-sensitive reporter, A{beta}42-CypHer, to track A{beta} internalisation in real time, demonstrating that oligomers are rapidly taken up into cells in a dynamin-dependent manner, and trafficked via the endo-lysosomal pathway resulting in accumulation in lysosomes. In contrast, a non-assembling variant of A{beta}42 (vA{beta}42) assayed in the same way is not internalised. Tracking ovalbumin uptake into cells using CypHer or Alexa Fluor tags shows that preincubation with A{beta}42 significantly disrupts protein uptake. Our results identify a potential mechanism by which amyloidogenic aggregates directly impair cellular function through disruption of the endosomal-lysosomal pathway.

neuroscience↗

bioRxiv2018

Poly(ADP-ribose) Polymerase-1 Hyperactivity at DNA Single-Strand Breaks Triggers Seizures and Shortened Lifespan

Defects in DNA single-strand break repair result in cerebellar ataxia which in Xrcc1Nes-Cre mice is promoted by hyperactivity of the DNA strand break sensor protein, Parp1. Here, we show that Parp1 hyperactivity extends beyond the cerebellum in Xrcc1-defective brain, resulting in lethal seizures and shortened lifespan. We demonstrate that aberrant Parp1 activation triggers seizure-like activity in Xrcc1-defective hippocampus ex vivo and aberrant presynaptic calcium signalling in isolated hippocampal neurons in vitro. Moreover, we show that these defects are prevented by Parp1 inhibition and/or deletion. Collectively, these data identify aberrant Parp1 activity at unrepaired DNA breaks as a cell-autonomous source of deregulated presynaptic calcium signalling, and highlight PARP inhibition as a possible therapeutic approach in XRCC1-mutated neurodegenerative disease. SummaryPARP1 activity and presynaptic Ca2+ signalling

neuroscience↗

bioRxiv2018

A central control circuit for encoding perceived food value

Hunger state can substantially alter the perceived value of a stimulus, even to the extent that the same sensory cue can trigger antagonistic behaviors. How the nervous system uses such graded perceptual shifts to select between opposed motor patterns remains enigmatic. Here we challenged food-deprived and satiated Lymnaea to choose between two mutually exclusive behaviors, ingestion or egestion, produced by the same feeding central pattern generator. Decoding the underlying neural circuit reveals that the activity of central dopaminergic interneurons defines hunger state and drives network reconfiguration, biasing satiated animals towards the rejection of stimuli deemed palatable by food-deprived ones. By blocking the action of these neurons, satiated animals can be reconfigured to exhibit a hungry animal phenotype. This centralized mechanism occurs in the complete absence of sensory retuning and generalizes across different sensory modalities, allowing food-deprived animals to increase their perception of food value in a stimulus-independent manner to maximize potential calorific intake.

neuroscience↗