Biology subjects

Nabbout, R.

Publications and source records attributed to Nabbout, R..

4 recordsLinked to original sources

bioRxiv2025

Multiplex imaging combined to machine learning enable automated profiling of cortical malformations applications in tuberous sclerosis complex

Malformations of cortical development such as tuberous sclerosis complex arise within a heterogeneous cellular landscape that conventional histopathology only partially resolves. Here, we combined a 19-marker multiplex immunofluorescence panel with a machine learning-driven image analysis pipeline to map and quantify over 365 000 cells from paediatric surgical cortex, defining the single-cell architecture of TSC lesions. Microtubers were objectively delineated by vimentin and detected in all TSC samples but absent from non-dysplastic controls. Within these structures, balloon cells exhibiting strong pS6 activation occupied lesion cores and were confined to microtuber boundaries, whereas dysmorphic neurons were more diffusely distributed into adjacent cortex. The microtuber niche was dominated by astroglial remodeling: immature and reactive vimentin-positive astrocytes, including Lamp5-positive subsets, accumulated at and around lesion rims, while mature GFAP-positive astrocytes showed only modest changes. Distance-based spatial analyses revealed neuronal exclusion from microtuber centres with gradual recovery in surrounding tissue, indicating local network disruption. Unsupervised clustering and niche modelling recapitulated these spatial gradients, identifying a glial-dominated ecosystem that concentrates balloon cells, increases inter-neuronal distances, and reduces cell-cell interactions. Together, these data support a model in which cortical tubers arise through the coalescence of microtubers orchestrated by balloon cells and reactive gliosis during corticogenesis. Beyond elucidating disease architecture, our automated framework enables reproducible lesion detection, quantitative cell-state mapping, and spatial readouts applicable across malformations of cortical development. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=126 SRC="FIGDIR/small/690101v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@dc3258org.highwire.dtl.DTLVardef@6d4149org.highwire.dtl.DTLVardef@d93354org.highwire.dtl.DTLVardef@1b8f83d_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

Functional assessment of a kcnb1 knock-out zebrafish to model KCNB1-related neurodevelopmental and epileptic disorders

KEY POINTSO_LIkcnb1 is expressed in distinct cell subtypes and various regions of the central nervous system in zebrafish C_LIO_LIBrain anatomy and neuronal circuits are not disrupted in the kcnb1 loss-of-function zebrafish model C_LIO_LILoss of kcnb1 leads to altered behavior phenotype, light and sound-induced locomotor impairments C_LIO_LIkcnb1 knock-out zebrafish exhibit increased locomotor sensitivity to PTZ and elevated expression of epileptogenesis-related genes C_LIO_LIkcnb1-/- larvae show spontaneous and provoked epileptiform-like electrographic activity associated with disrupted GABA regulation C_LI ObjectiveKCNB1 encodes an -subunit of the delayed-rectifier voltage-dependent potassium channel Kv2.1. De novo pathogenic variants of KCNB1 have been linked to developmental and epileptic encephalopathies (DEE), diagnosed in early childhood and sharing limited treatment options. Loss-of-function (LOF) of KCNB1 with dominant negative effects has been proposed as the pathogenic mechanism in these disorders. Here, we aim to characterize a knock-out (KO) zebrafish line targeting kcnb1 (kcnb1+/- and kcnb1-/-) for investigating DEEs. MethodsThis study presents the phenotypic analysis of a kcnb1 knock-out zebrafish model, obtained by CRISPR/Cas9 mutagenesis. Through a combination of immunohistochemistry, behavioral assays, electrophysiological recordings, and neurotransmitter quantifications, we have characterized the expression, function, and impact of this kcnb1 LOF model at early stages of development. ResultsIn wild-type larval zebrafish, kcnb1 was found in various regions of the central nervous system and in diverse cell subtypes including neurons, oligodendrocytes and microglial cells. Both kcnb1+/- and kcnb1-/- zebrafish displayed impaired swimming behavior and "epilepsy-like" features that persisted through embryonic and larval development, with variable severity. When exposed to the chemoconvulsant pentylenetetrazol (PTZ), both mutant models showed elevated locomotor activity. In addition, PTZ-exposed kcnb1-/- larvae exhibited higher bdnf mRNA expression and activated c-Fos positive neurons in the telencephalon. This same model presents spontaneous and provoked epileptiform-like electrographic activity associated with disrupted GABA regulation. In this KO model, neuronal circuit organization remained unaffected. SignificanceWe conclude that kcnb1 knock-out in zebrafish leads to early-onset phenotypic features reminiscent of DEEs, affecting neuronal functions and primarily inhibitory pathways in developing embryonic and larval brains. This study highlights the relevance of this model for investigating developmental neuronal signaling pathways in KCNB1-related DEEs.

neuroscience↗

bioRxiv2023

Preictal dysfunctions of inhibitory interneurons paradoxically lead to their rebound hyperactivity and to Low-Voltage-Fast onset seizures in Dravet syndrome.

Epilepsies have numerous specific mechanisms. Understanding neural dynamics leading to seizures is important for disclosing pathological mechanisms and developing targeted therapeutic approaches. We investigated electrographic activities and neural dynamics leading to convulsive seizures in patients and mouse models of Dravet syndrome (DS), a developmental and epileptic encephalopathy in which hypoexcitability of GABAergic neurons is considered to be the main dysfunction. We analyzed EEGs from DS patients carrying a SCN1A pathogenic variant, as well as epidural electrocorticograms, hippocampal local field potentials and hippocampal single-unit neuronal activities in Scn1a+/- knock-out and Scn1aRH/+ knock-in DS mice. Strikingly, most seizures had low-voltage-fast onset in both patients and mice, which is thought to be generated by hyperactivity of GABAergic interneurons, the opposite of the main pathological mechanism of DS. Analyzing single unit recordings, we observed that temporal disorganization of the firing of putative interneurons in the period immediately before the seizure (preictal period) precedes the increase of their activity at seizure onset, together with the entire neuronal network. Moreover, we found early signatures of the preictal period in the spectral features of hippocampal and cortical field potential of Scn1a mice and of patients EEG, which are consistent with the dysfunctions that we observed in single neurons. Therefore, the perturbed preictal activity of interneurons leads to their hyperactivity at the onset of generalized seizures, which have low-voltage-fast features that are similar to those observed in other epilepsies and are triggered by hyperactivity of GABAergic neurons. Spectral features may be used as predictive seizure biomarker. Significance statementDravet syndrome (DS) is caused by mutations of the NaV1.1 sodium channel (SCN1A gene) leading to hypoexcitability of GABAergic interneurons. We found that most of the seizures in both DS patients and mouse models have low-voltage-fast onset, which is instead thought to be generated by hyperactivity of GABAergic neurons. We disclosed a disorganization in the temporal pattern of the firing of single interneurons before the seizure (preictal period), and a rebound hyperactivity at seizure onset. Consistently, the electrographic signal showed a decrease of fast oscillations in the preictal period. Thus, perturbed interneurons preictal activity, consistent with the main mechanism of DS, leads to their hyperactivity at seizure onset and induces specific electrographic signatures that may be exploited for seizure prediction.

neuroscience↗

bioRxiv2019

Functional cortico-subcortical reorganization after complete hemispheric disconnection for intractable epilepsy

Hemispherotomy is a treatment for drug-resistant epilepsy with the whole hemisphere involved in seizure onset. As recovery mechanisms are still debated, we characterize functional reorganization with multimodal MRI in two children operated on the right hemisphere (RH). We found that interhemispheric functional connectivity was abolished in both patients. The healthy left hemispheres (LH) displayed focal hyperperfusion in motor and limbic areas, and preserved network-level organization. The disconnected RHs were hypoperfused despite sustained network-level organization. Functional connectivity was increased in the left thalamo-cortical loop and between the cerebelli. The classification probability of the RH corresponding to a minimally conscious state was smaller than for the LH. We conclude that after hemispherotomy, neurological rehabilitation is sustained by cortical disinhibition and reinforcement of connectivity driven by subcortical structures in the remaining hemisphere. Our results highlight the effect of vascularization on functional connectivity and raise inquiries about the conscious state of the isolated hemisphere.

neuroscience↗