Biology subjects

Baraban, S. C.

Publications and source records attributed to Baraban, S. C..

10 recordsLinked to original sources

bioRxiv2026

Virtual screening and zebrafish phenotype-based evaluation argues against repurposing 4-phenylbutyrate for STXBP1-relateddisorders

Syntaxin-binding protein 1 (STXBP1) mutations lead to severe epilepsy, intellectual disability, developmental delay, and movement disorder. Effective treatments for these conditions do not exist. Recent studies in Munc18-1 (STXBP1) C. elegans models demonstrate that 4-phenylbutyrate (4-PBA) or related pharmacological chaperones stabilize Munc18-1 protein levels and rescue locomotion deficits. These studies suggest a novel treatment strategy for these patients. Here, we used a stxbp1a zebrafish model with a profound movement disorder to screen 4-PBA and alternative structural analogs identified using artificial intelligence (AI)-based screening. Automated locomotion assays conducted on larval stxbp1a mutant zebrafish at 5 days post-fertilization (dpf) confirm and extend the movement disorder endophenotype. Drug treatment (4-PBA or 16 identified candidates) failed to rescue the stxbp1a mutant zebrafish locomotion deficit. Electrophysiology studies in a stxbp1b zebrafish model characterized by spontaneous seizure activity (i.e., epilepsy) failed to detect a reduction in ictal-like events with 4-PBA treatment. Taken together, our results suggest caution in repurposing 4-PBA or related compounds for treatment of STXBP1 disorders.

pharmacology and toxicology↗

bioRxiv2024

Zebrafish models of human-duplicated gene SRGAP2 reveal novel functions in microglia and visual system development

The expansion of the human SRGAP2 family, resulting in a human-specific paralog SRGAP2C, likely contributed to altered evolutionary brain features. The introduction of SRGAP2C in mouse models is associated with changes in cortical neuronal migration, axon guidance, synaptogenesis, and sensory-task performance. Truncated SRGAP2C heterodimerizes with the full-length ancestral gene product SRGAP2A and antagonizes its functions. However, the significance of SRGAP2 duplication beyond neocortex development has not been elucidated due to the embryonic lethality of complete Srgap2 knockout in mice. Using zebrafish, we show that srgap2 knockout results in viable offspring and that these larvae phenocopy "humanized" SRGAP2C larvae, including altered morphometric features (i.e., reduced body length and inter-eye distance) and differential expression of synapse-, axonogenesis-, and vision-related genes. Through single-cell transcriptome analysis, we demonstrate a skewed balance of excitatory and inhibitory neurons that likely contribute to increased susceptibility to seizures displayed by Srgap2 mutant larvae, a phenotype resembling SRGAP2 loss-of-function in a child with early infantile epileptic encephalopathy. Single-cell data also shows strong endogenous expression of srgap2 in microglia with mutants exhibiting altered membrane dynamics and likely delayed maturation of microglial cells. Microglia cells expressing srgap2 were also detected in the developing eye together with altered expression of genes related to axonogenesis in mutant retinal cells. Consistent with the perturbed gene expression in the retina, we found that SRGAP2 mutant larvae exhibited increased sensitivity to broad and fine visual cues. Finally, comparing the transcriptomes of relevant cell types between human (+SRGAP2C) and non-human primates (-SRGAP2C) revealed significant overlaps of gene alterations with mutant cells in our zebrafish models; this suggests that SRGAP2C plays a similar role altering microglia and the visual system in modern humans. Together, our functional characterization of conserved ortholog Srgap2 and human SRGAP2C in zebrafish uncovered novel gene functions and highlights the strength of cross-species analysis in understanding the development of human-specific features. Abstract (short)SRGAP2C has been implicated in contributing to altered brain features in the evolution of humans. However, the significance of SRGAP2 duplication beyond neocortex development has not been elucidated due to the embryonic lethality of complete Srgap2 knockout in mice. Using zebrafish, we show that srgap2 knockout results in viable offspring that phenocopy "humanized" SRGAP2C larvae. Morphometric, behavioral, and transcriptome analyses collectively suggest srgap2 impacts axonal guidance, synaptogenesis, and seizure susceptibility. Beyond neurons, Srgap2 functions in controlling membrane dynamics and maturation of microglial cells, possibly leading to altered axonogenesis in the developing retina and increased sensitivity to broad and fine visual cues. Comparing relevant transcriptomes between human and nonhuman primates suggests that SRGAP2C similarly impacts microglia and vision in modern humans. Our functional characterization of conserved ortholog Srgap2 and human SRGAP2C in zebrafish uncovered novel gene functions and highlights the strength of cross-species analysis in understanding the development of human-specific features.

genomics↗

bioRxiv2024

Host brain environmental influences on transplanted medial ganglionic eminence progenitors

Interneuron progenitor transplantation can ameliorate disease symptoms in a variety of neurological disorders. This strategy is based on transplantation of embryonic medial ganglionic eminence (MGE) progenitors. Elucidating host brain environment influences on interneuron progenitors as they integrate is critical to optimizing this strategy across different disease states. Here, we systematically evaluated age and brain region influences on survival, migration and differentiation of transplant-derived cells. We find that early postnatal MGE transplantation yields superior survival and more extensive migratory capabilities compared to juvenile or adult. MGE progenitors migrate more widely in cortex compared to hippocampus. Maturation to interneuron subtypes is regulated by age and brain region. MGE progenitors transplanted into dentate gyrus sub-region of early postnatal hippocampus can differentiate into astrocytes. Our results suggest that host brain environment critically regulates survival, spatial distribution and maturation of MGE-derived interneurons following transplantation. These findings inform and enable optimal conditions for interneuron transplant therapies.

neuroscience↗

bioRxiv2023

Testing of putative antiseizure drugs in a preclinical Dravet syndrome zebrafish model

Dravet syndrome (DS) is a severe genetic epilepsy primarily caused by de novo mutations in a voltage-activated sodium channel gene (SCN1A). Patients face life-threatening seizures that are largely resistant to available anti-seizure medications (ASM). Preclinical DS animal models are a valuable tool to identify candidate ASMs for these patients. Among these, scn1lab mutant zebrafish exhibiting spontaneous seizure-like activity are particularly amenable to large-scale drug screening. Prior screening in a scn1lab mutant zebrafish line generated using N-ethyl-N-nitrosourea (ENU) identified valproate, stiripentol, and fenfluramine e.g., Federal Drug Administration (FDA) approved drugs with clinical application in the DS population. Successful phenotypic screening in scn1lab mutant zebrafish consists of two stages: (i) a locomotion-based assay measuring high-velocity convulsive swim behavior and (ii) an electrophysiology-based assay, using in vivo local field potential (LFP) recordings, to quantify electrographic seizure-like events. Using this strategy more than 3000 drug candidates have been screened in scn1lab zebrafish mutants. Here, we curated a list of nine additional anti-seizure drug candidates recently identified in preclinical models: 1-EBIO, AA43279, chlorzoxazone, donepezil, lisuride, mifepristone, pargyline, soticlestat and vorinostat. First-stage locomotion-based assays in scn1lab mutant zebrafish identified only 1-EBIO, chlorzoxazone and lisuride. However, second-stage LFP recording assays did not show significant suppression of spontaneous electrographic seizure activity for any of the nine anti-seizure drug candidates. Surprisingly, soticlestat induced frank electrographic seizure-like discharges in wild-type control zebrafish. Taken together, our results failed to replicate clear anti-seizure efficacy for these drug candidates highlighting a necessity for strict scientific standards in preclinical identification of ASMs.

neuroscience↗

bioRxiv2022

Clemizole and Trazodone are Effective Antiseizure Treatments in a Zebrafish Model of STXBP1 Disorder

ObjectiveCRISPR-Cas9-generated zebrafish carrying a 12 base-pair deletion in stxbpb1b, a paralog sharing 79% amino acid sequence identity with human, exhibit spontaneous electrographic seizures during larval stages of development. Zebrafish stxbp1b mutants provide an efficient preclinical platform to test antiseizure therapeutics. The present study was designed to test prototype antiepileptic drugs approved for clinical use and two recently identified repurposed drugs with antiseizure activity. MethodsLarval homozygous stxbp1b zebrafish (4 days post-fertilization) were agarose-embedded and monitored for electrographic seizure activity using a local field recording electrode placed in midbrain. Frequency of ictal-like events was evaluated at baseline and following 45 min of continuous drug exposure (1 mM, bath application). Analysis was performed on coded files by an experimenter blinded to drug treatment and genotype. ResultsPhenytoin, valproate, ethosuximide, levetiracetam, and diazepam had no effect on ictal-like event frequency in stxbp1b mutant zebrafish. Clemizole and trazodone decreased ictal-like event frequency in stxbp1b mutant zebrafish by 80% and 83%, respectively. These results suggest that repurposed drugs with serotonin receptor binding affinities could be effective antiseizure treatments. SignificanceClemizole and trazodone were identified in a larval zebrafish model for Dravet syndrome. Based primarily on these preclinical zebrafish studies, compassionate-use and double-blind clinical trials with both drugs have progressed. The present study extends this approach to a preclinical zebrafish model representing STXBP1-related disorders, and suggests that future clinical studies may be warranted.

neuroscience↗

bioRxiv2021

Xenotransplantation of porcine progenitor cells in an epileptic California sea lion (Zalophus californianus)

BackgroundDomoic acid (DA) is a naturally occurring neurotoxin harmful to marine animals and humans. California sea lions exposed to DA in prey during algal blooms along the Pacific coast exhibit significant neurological symptoms, including epilepsy with hippocampal atrophy. ObservationsHere we describe a xenotransplantation procedure to deliver interneuron progenitor cells into the damaged hippocampus of an epileptic sea lion with suspected DA toxicosis. The sea lion has had no evidence of seizures following the procedure, and clinical measures of well-being including weight and feeding habits have stabilized. LessonsThese preliminary results suggest xenotransplantation has improved the quality-of-life (QOL) for this animal and holds tremendous therapeutic promise.

neuroscience↗

bioRxiv2021

Phenotypic analysis of catastrophic childhood epilepsy genes: The Epilepsy Zebrafish Project

Genetic engineering techniques have contributed to the now widespread use of zebrafish to investigate gene function, but zebrafish-based human disease studies, and particularly for neurological disorders, are limited. Here we used CRISPR-Cas9 to generate 40 single-gene mutant zebrafish lines representing catastrophic childhood epilepsies. We evaluated larval phenotypes using electrophysiological, behavioral, neuro-anatomical, survival and pharmacological assays. Phenotypes with unprovoked electrographic seizure activity (i.e., epilepsy) were identified in zebrafish lines for 8 genes; ARX, EEF1A, GABRB3, GRIN1, PNPO, SCN1A, STRADA and STXBP1. A unifying epilepsy classification scheme was developed based on local field potential recordings and blinded scoring from ~3300 larvae. We also created an open-source database containing sequencing information, survival curves, behavioral profiles and representative electrophysiology data. We offer all zebrafish lines as a resource to the neuroscience community and envision them as a starting point for further functional analysis and/or identification of new therapies.

neuroscience↗

bioRxiv2020

Interneuron origins in the embryonic porcine medial ganglionic eminence

Interneurons contribute to the complexity of neural circuits and maintenance of normal brain function. Rodent interneurons originate in embryonic ganglionic eminences, but developmental origins in other species are less understood. Here, we show that transcription factor expression patterns in porcine embryonic subpallium are similar to rodents, delineating a distinct medial ganglionic eminence (MGE) progenitor domain. On the basis of Nkx2.1, Lhx6 and Dlx2 expression, in vitro differentiation into neurons expressing GABA and robust migratory capacity in explant assays, we propose that cortical and hippocampal interneurons originate from a porcine MGE region. Following xenotransplantation into adult male and female rat hippocampus, we further demonstrate that porcine MGE progenitors, like those from rodents, migrate and differentiate into morphologically distinct interneurons expressing GABA. Our findings reveal that basic rules for interneuron development are conserved across species, and that porcine embryonic MGE progenitors could serve as a valuable source for interneuron-based xenotransplantation therapies. Significance StatementHere we demonstrate that porcine MGE, like rodents, exhibit a distinct transcriptional and pallial interneuron-specific antibody profile, in vitro migratory capacity and are amenable to xenotransplantation. This is the first comprehensive examination of embryonic pallial interneuron origins in the pig, and because a rich neurodevelopmental literature on embryonic mouse MGE exists (with some additional characterizations in other species like monkey and human) our work allows direct neurodevelopmental comparisons with this literature.

neuroscience↗

bioRxiv2020

Higher-order hub cells involved in feedforward motifs as critical factors in epileptic network instability

Neurological and psychiatric disorders are associated with pathological neural dynamics. The fundamental connectivity patterns of cell-cell communication networks that enable pathological dynamics to emerge remain unknown. We studied epileptic circuits using a newly developed integrated computational pipeline applied to cellular resolution functional imaging data. Control and preseizure neural dynamics in larval zebrafish and in chronically epileptic mice were captured using large-scale cellular-resolution calcium imaging. Biologically constrained effective connectivity modeling extracted the underlying cell-cell communication network. Novel analysis of the higher-order network structure revealed the existence of superhub cells that are unusually richly connected to the rest of the network through feedforward motifs. Instability in epileptic networks was causally linked to superhubs whose involvement in feedforward motifs critically enhanced downstream excitation. Disconnecting individual superhubs was significantly more effective in stabilizing epileptic networks compared to disconnecting hub cells defined traditionally by connection count. Collectively, these results predict a new, maximally selective and minimally invasive cellular target for seizure control. HighlightsO_LIHigher-order connectivity patterns of large-scale neuronal communication networks were studied in zebrafish and mice C_LIO_LIControl and epileptic networks were modeled from in vivo cellular resolution calcium imaging data C_LIO_LIRare superhub cells unusually richly connected to the rest of the network through higher-order feedforward motifs were identified C_LIO_LIDisconnecting single superhub neurons more effectively stabilized epileptic networks than targeting conventional hub cells defined by high connection count. C_LIO_LIThese data predict a maximally selective novel single cell target for minimally invasive seizure control C_LI

neuroscience↗

bioRxiv2019

Phenotype-based screening of synthetic cannabinoids in a Dravet Syndrome zebrafish model

Dravet syndrome (DS) is a catastrophic epilepsy of childhood, characterized by cognitive impairment, severe seizures and increased risk for sudden unexplained death in epilepsy (SUDEP). Although refractory to conventional antiepileptic drugs, emerging preclinical and clinical evidence suggests that modulation of the endocanniboid system could be therapeutic in these patients. Here we used a validated zebrafish model of DS, scn1lab homozygous mutants, to screen a commercially available library containing 370 synthetic cannabinoid (SC) compounds for compounds effective in reducing spontaneous seizures. Primary phenotype-based screening was performed using a locomotion-based assay in 96-well plates, and a secondary local field potential recording assay was then used to confirm suppression of electrographic epileptiform events. Identified SCs with anti-seizure activity, in both assays, included five SCs structurally classified as indole-based cannabinoids: JWH 018 N-(5-chloropentyl) analog, JWH 018 N-(2-methylbutyl) isomer, 5-fluoro PB-22 5-hydroxyisoquinoline isomer, 5-fluoro ADBICA, and AB-FUBINACA 3-fluorobenzyl isomer. Our approach demonstrates that two-stage phenotype-based screening in a zebrafish model of DS successfully identifies synthetic cannabinoids with anti-seizure activity, and supports further investigation of SCs for refractory epilepsies.

neuroscience↗