Biology subjects

Neves, G.

Publications and source records attributed to Neves, G..

7 recordsLinked to original sources

bioRxiv2025

Increased HCN1 activity in human excitatory neurons drives excessive network bursting in Dravet syndrome

Dravet syndrome (DS) is a severe childhood epilepsy caused by mutations of the sodium channel NaV1.1. These mutations are thought to compromise the ability of inhibitory interneurons to regulate network activity, leading to seizure events. However, standard treatments to restore inhibition have limited efficacy, suggesting the existence of additional pathological mechanisms. Here, we use hiPSC-derived neuronal networks containing both excitatory and inhibitory neurons to show that excessive bursting activity in DS cultures is driven by excitatory neurons. This rise in bursting frequency is caused by the increased expression of HCN1 "pacemaker" channels in excitatory neurons, and bursting activity can be normalised using a channel blocker. With this work, we propose a new pathophysiological mechanism in DS and identify HCN1 as a novel therapeutic target.

neuroscience↗

bioRxiv2024

Semi-automated navigation for efficient targeting of electron tomography to regions of interest in volume correlative light and electron microscopy

Electron microscopy is essential for the quantitative study of synaptic ultrastructure. At present, the correlation of functional and structural properties of the same synapse is extremely challenging. We introduce a novel integrated workflow designed to simplify sample navigation across spatial scales, allowing the identification of individual synapses from optical microscopy mouse brain image stacks that can be targeted for analysis using electron tomography imaging. We developed a software which has a function to register multimodal images using a novel segmentation-based image registration algorithm as well as a function to visualize all the registration results. Using our newly designed software we streamline mapping of high-resolution optical imaging onto reference maps using blood vessels as endogenous fiducial marks. Further we demonstrate significant improvements on the ultramicrotomy stage of volume Correlative Light and Electron Microscopy (vCLEM) workflows, providing real time guidance to targeted trimming to match previously acquired Regions Of Interest (ROIs), and reliable estimates of cutting depth relative to ROI, based on fluorescence imaging of TEM ready ultrathin sections. Using this workflow, we successfully targeted TEM tomography to the proximal axonal region containing the Axon Initial Segment identified using fluorescent light microscopy.

neuroscience↗

bioRxiv2024

Excitatory and inhibitory synapses form a tight subcellular balance along dendrites that decorrelates over development

A balance between excitation and inhibition is crucial for neurotypical brain function. Indeed, disruptions in this relationship are frequently associated with the pathophysiology of neurodevelopmental disorders. Nevertheless, how this balance is established during the dynamic period of neurodevelopment remains unexplored. Using multiple techniques, including in utero electroporation, electron microscopy and electrophysiology, we reveal a tight correlation in the distribution of excitatory and inhibitory synapses along dendrites of developing CA1 hippocampal neurons. This balance was present within short dendritic stretches (<20{micro}m), and surprisingly, was most pronounced during early development, sharply declining with maturity. The tight matching between excitation and inhibition was unexpected, as inhibitory synapses lacked an active zone when formed and exhibited compromised evoked release. We propose that inhibitory synapses form as a stabilising scaffold, to counterbalance growing excitation levels. This relationship diminishes over time, suggesting a critical role for a subcellular balance in early neuronal function and circuit formation.

neuroscience↗

bioRxiv2022

Multi-synaptic boutons are a feature of CA1 hippocampal connections that may underlie network synchrony

Excitatory synapses are typically described as single synaptic boutons (SSBs), where one presynaptic bouton contacts a single postsynaptic spine. Using serial section block face scanning electron microscopy, we found that this textbook definition of the synapse does not fully apply to the CA1 region of the hippocampus. Roughly half of all excitatory synapses in the stratum oriens involved multi-synaptic boutons (MSBs), where a single presynaptic bouton containing multiple active zones contacted many postsynaptic spines (from 2 to 7) on the basal dendrites of different cells. The fraction of MSBs increased during development (from P21 to P100) and decreased with distance from the soma. Curiously, synaptic properties such as active zone (AZ) or postsynaptic density (PSD) size exhibited less within-MSB variation when compared to neighbouring SSBs, features that were confirmed by super-resolution light microscopy. Computer simulations suggest that these properties favour synchronous activity in CA1 networks.

neuroscience↗

bioRxiv2022

Pathogenic TDP-43 Disrupts Axon Initial Segment Structure and Neuronal Excitability in a Human iPSC Model of ALS

Dysregulated neuronal excitability is a hallmark of amyotrophic lateral sclerosis (ALS). We sought to investigate how functional changes to the axon initial segment (AIS), the site of action potential generation, could impact neuronal excitability in a human iPSC model of ALS. We found that early (6-week) ALS-related TDP-43G298S motor neurons showed an increase in the length of the AIS, relative to CRISPR-corrected controls. This was linked to neuronal hyperexcitability and increased spontaneous contractions of hiPSC-myofibers in compartmentalised neuromuscular co-cultures. In contrast late (10-week) TDP-43G298S motor neurons showed reduced AIS length and hypoexcitability. At a molecular level aberrant expression of the AIS master scaffolding protein Ankyrin-G, and the AIS-specific voltage-gated ion channels SCN1A (Nav1.1) and SCN8A (Nav1.6) mirrored these dynamic changes in excitability. Finally, at all stages, TDP-43G298S motor neurons showed compromised activity-dependent plasticity of the AIS, further contributing to abnormal excitability. Our results point toward the AIS as an important subcellular target driving changes to neuronal excitability in ALS.

neuroscience↗

bioRxiv2017

Neonatal Zika virus infection causes epileptic seizures, viral persistence and long-term behavioral impairment

A causal relationship between congenital Zika virus (ZIKV) exposure and microcephaly and other neurological disorders have been established, but long-term consequences of infection are still unknown. We evaluated acute and late neuropathological and behavioral consequences of ZIKV infection in a neonatal immunocompetent mouse model. ZIKV showed brain tropism, causing post-natal microcephaly and several behavioral dysfunctions. During the acute phase of infection, mice developed very frequent epileptic seizures, which are consistently reduced by TNF- neutralization. Although adult animals recover from seizures, they become more susceptible to chemically-induced crises. Intriguingly, the virus remained actively replicating in adult animals, which show persistent necrosis and calcifications in the mice brain. Altogether the results reveal late consequences of neonatal ZIKV exposure and suggest the early inhibition of neuroinflammation as a potential treatment.

neuroscience↗

bioRxiv2017

Activity-Dependent Control Of Inhibitory Interneuron Number In The Mammalian Cortex

Cortical networks are composed of excitatory projection neurons and inhibitory interneurons. Finding the right balance between the two is important for controlling overall cortical excitation and network dynamics. However, it is unclear how the correct number of cortical interneurons (CIs) is established in the mammalian forebrain. CIs are generated in excess from basal forebrain progenitors and their final numbers are adjusted via an intrinsically determined program of apoptosis that takes place during an early postnatal window. Here, we provide evidence that the extent of CI apoptosis during this critical period is plastic, cell type specific and can be reduced in a cell autonomous manner by acute increases in neuronal activity. We propose that the physiological state of the emerging neural network controls the activity levels of local CIs to modulate their numbers in a homeostatic manner.

neuroscience↗