Biology subjects

Neuhauss, S. C. F.

Publications and source records attributed to Neuhauss, S. C. F..

12 recordsLinked to original sources

bioRxiv2025

A Novel Zebrafish Luminescent Biosensor for Kidney Tubulopathy, Metal Toxicity, and Drug Screening

An efficient endo-lysosomal pathway is crucial to mediate the reabsorption and processing of ultrafiltered solutes including low-molecular-weight (LMW) proteins by the epithelial cells lining the proximal tubule (PT) of the kidney. The zebrafish pronephros is increasingly used as a model system for congenital or acquired disorders that impair the endocytic uptake in PT cells, that cause an inappropriate loss of solutes and LMW proteins in the urine. Here, we describe a new reporter zebrafish line, termed[1/2] vdbp-NanoLuc, in which the vitamin D-binding protein is coupled to NanoLuc luciferase, for rapid, large-scale detection of PT dysfunction and LMW proteinuria. We demonstrate the reliability and value of the[1/2] vdbp-NanoLuc biosensor in fish models of monogenic endolysosomal diseases, gentamicin and cisplatin-induced nephrotoxicity, and metal contamination. This novel system provides mechanistic insights into the cadmium- and copper-induced PT dysfunction and, when combined with a swimming test, a platform for drug screening to alleviate cisplatin toxicity.

pharmacology and toxicology↗

bioRxiv2024

Inhibition mediated by group III mGluRs regulates habenula activity and defensive behaviors

Inhibition contributes to various brain computations from sensory motor transformations to cognitive operations. While most studies on inhibition focus on GABA, the main excitatory neurotransmitter of the brain, glutamate, can also elicit inhibition via metabotropic glutamate receptors (mGluRs). The function of mGluR-mediated inhibition remains largely elusive. Here, we investigated the role of group III mGluR-dependent inhibition in the habenula. This primarily glutamatergic and conserved forebrain region acts as a hub between multiple forebrain inputs and neuromodulatory mid- and hindbrain targets that regulate adaptive behaviors. We showed that both zebrafish and mice habenula express group III mGluRs. We identified that group III mGluRs regulate the membrane potential and calcium activity of zebrafish dorsal habenula. Pharmacological and genetic perturbation of group III mGluRs increased sensory-evoked excitation and reduced selectivity of habenular neurons to different sensory modalities. We also observed that inhibition is the main channel of communication between primarily glutamatergic habenula neurons. Blocking group III mGluRs reduced inhibition within habenula and increased correlations during spontaneous activity. In line with such inhibition within habenula, we identified that multi-sensory information is integrated mainly through competition and suppression across habenular neurons, which in part relies on group III mGluRs. Finally, genetic perturbation of a habenula-specific group III mGluR, mGluR6a, amplified neural responses and defensive behaviors evoked by sensory stimulation and environmental changes. Altogether, our results revealed that mGluR driven inhibition is essential in encoding, integration, and communication of information between Hb neurons, ultimately playing a critical role in regulating defensive and adaptive behaviors.

neuroscience↗

bioRxiv2024

Magnetoelectric Microrobots for Spinal Cord Injury Regeneration

Regenerative medicine continually seeks effective methods to address spinal cord injuries (SCI), which are known for their limited regenerative potential. Despite advances in neural progenitor cell (NPC) transplants for spinal cord injuries, challenges related to graft survival, reliable in vivo differentiation, and neural integration significantly hinder real functional recovery and limit clinical outcomes. This study introduces NPCbots, biohybrid microrobots engineered by integrating human-induced pluripotent stem cell-derived NPCs with magnetoelectric nanoparticles composed of cobalt ferrite-barium titanate. These enable magnetic navigation and neuronal stimulation, enhancing targeted therapeutic interventions. Our lab-on-a-chip system allows for the mass production of NPCbots, ensuring their differentiation and biocompatibility. Remarkably, in a zebrafish model of SCI, NPCbots stimulated by an alternating magnetic field demonstrated rapid in vivo differentiation and integration into damaged neural pathways, significantly enhancing neural regeneration. Within three days, injured zebrafish treated with NPCbots exhibited almost normal swimming behavior and significantly improved exploratory behavior, showcasing the potential of NPCbots to swiftly repair neural structures and restore the central nervous systems functionality in spinal cord injury models through non-invasive means. Additionally, precise in vitro and in vivo manipulation of NPCbots indicates their broader application in various neurodegenerative disorders, offering a promising route for effective spinal cord and neurological recovery.

neuroscience↗

bioRxiv2022

Reflective multi-immersion microscope objectives inspired by the Schmidt telescope

Rapid advances in tissue clearing protocols have begun to outpace the capabilities of existing microscope objectives: High-resolution imaging inside cm-sized cleared samples is often not possible as it requires multi-immersion objectives with high numerical aperture (NA > 0.7), long working distance (WD > 10 mm) and a large field-of-view (FOV > 1 mm). Here, we introduce a novel mirror-based optical design, the "Schmidt objective", which meets all these criteria despite containing only two optical elements. It consists of a spherical mirror in contact with the immersion medium and an aspherical correction plate. We showcase a multi-photon variant of a Schmidt objective that reaches NA 1.08 at an refractive index of 1.56 and demonstrate its versatility by imaging fixed samples in a wide range of immersion media ranging from air and water to BABB, DBE, and ECI. In addition, we demonstrate in vivo imaging by recording neuronal activity in larval zebrafish.

neuroscience↗

bioRxiv2022

Elevated photic response is followed by a rapid decay and depressed state in ictogenic networks

The switch between non-seizure and seizure states involves profound alterations in network excitability and synchrony. Both increased and decreased excitability may underlie the state transitions, as shown in epilepsy patients and animal models. Inspired by video-electroencephalography recordings in patients, we developed a framework to study spontaneous and photic-evoked neural and locomotor activity in zebrafish larvae. We combined high-throughput behavioral tracking and whole-brain in vivo two-photon calcium imaging to perform side-by-side comparison of multiple zebrafish seizure and epilepsy models. Our setup allowed us to dissect behavioral and physiological features that are divergent or convergent across multiple models. We observed that locomotor and neural activity during interictal and spontaneous ictal periods exhibit great diversity across models. Yet, during photic stimulation, hyperexcitability and rapid response dynamics was well conserved across multiple models, highlighting the reliability of photic-evoked seizure activity for high-throughput assays. Intriguingly, in several models, we observed that the initial elevated photic response is often followed by fast decay of neural activity and a prominent depressed state. We argue that such depressed states are likely due to homeostatic mechanisms triggered by excessive neural activity. An improved understanding of the interplay between elevated and depressed excitability states might suggest tailored epilepsy therapies. KEY POINTSO_LIFeatures of spontaneous locomotor and neural activity varies across zebrafish epilepsy and seizure models. C_LIO_LIWe propose photic stimulation as a reliable tool to investigate behavioral and physiological phenotypes in zebrafish epilepsy and seizure models. C_LIO_LIWe observed elevated activity with faster dynamics in response to photic stimulation in all tested zebrafish models. C_LIO_LIPhotic-evoked neural responses were often followed by depressed state in seizure-prone networks C_LI

neuroscience↗

bioRxiv2022

Mutation of Vsx genes in zebrafish highlights the robustness of the retinal specification network.

Genetic studies in human and mice have established a dual role for Vsx genes in retina development: an early function in progenitors specification, and a later requirement for bipolar-cells fate determination. Despite their conserved expression patterns, it is currently unclear to which extent Vsx functions are also conserved across vertebrates, as mutant models are available only in mammals. To gain insight into vsx function in teleosts, we have generated vsx1 and vsx2 CRISPR-Cas9 double knockouts (vsxKO) in zebrafish. Our electrophysiological and histological analyses indicate severe visual impairment and bipolar cells depletion in vsxKO larvae, with retinal precursors being rerouted towards photoreceptor or Muller glia fates. Surprisingly, neural retina is properly specified and maintained in mutant embryos, which do not display microphthalmia. We show that although important cis-regulatory remodelling occurs in vsxKO retinas during early specification, this has little impact at a transcriptomic level. Our observations point to genetic redundancy as an important mechanism sustaining the integrity of the retinal specification network, and to Vsx genes regulatory weight varying substantially among vertebrate species. Brief Summary Statement for use in emailed and online tables of content alertsThe mutation of vsx genes in zebrafish confirms a conserved role in bipolar cells specification across vertebrates, but do not interfere with the specification of the neural retina domain. Our data reveal the unexpected robustness of the genetic network sustaining the identity of the neural retina.

developmental biology↗

bioRxiv2022

FRaeppli, a multispectral imaging toolbox for cell tracing and dense tissue analysis in zebrafish

Visualizing cell shapes, interactions and lineages of differentiating cells is instrumental for understanding organ development and repair. Across species, strategies for stochastic multicolour labelling have greatly facilitated tracking cells in in vivo and mapping neuronal connectivity. Nevertheless, integrating multi-fluorophore information into the context of developing tissues in zebrafish is challenging given their cytoplasmic localization and spectral incompatibility with commonly used fluorescent markers. Here, we developed FRaeppli (Fish-Raeppli) expressing bright membrane-or nuclear-targeted fluorescent proteins for efficient cell shape analysis and tracking. High spatiotemporal activation flexibility is provided by the Gal4/UAS system together with Cre/lox and/or PhiC31integrase. The distinct spectra of the FRaeppli fluorescent proteins allow simultaneous imaging with GFP and infrared subcellular reporters or tissue landmarks. By tailoring hyperspectral protocols for time-efficient acquisition, we demonstrate FRaepplis suitability for live imaging of complex internal organs, like the liver. Combining FRaeppli with polarity markers revealed previously unknown canalicular topologies between differentiating hepatocytes, reminiscent of the mammalian liver, suggesting shared developmental mechanisms. The multispectral FRaeppli toolbox thus enables the comprehensive analysis of intricate cellular morphologies, topologies and tissue lineages at single-cell resolution in zebrafish.

developmental biology↗

bioRxiv2021

MAP4K4 determines cancer cell phenotype by controlling the plasma membrane-associated proteome

The composition of the plasma membrane (PM)-associated proteome of tumor cells determines cell-cell and cell-matrix interactions and the response to environmental cues. Whether the PM-associated proteome impacts the phenotype of Medulloblastoma (MB) tumor cells and how it adapts in response to growth factor cues is poorly understood. Using a spatial proteomics approach, we observed that hepatocyte growth factor (HGF)-induced activation of the receptor tyrosine kinase c-MET in MB cells changes the abundance of transmembrane and membrane-associated proteins. The depletion of MAP4K4, a pro-migratory effector kinase downstream of c-MET, leads to a specific decrease of the adhesion and immunomodulatory receptor CD155 and of components of the fast-endophilin-mediated endocytosis (FEME) machinery in the PM-associated proteome of HGF-activated MB cells. The decreased surface expression of CD155 or of the FEME effector Endophilin A1 reduces growth and invasiveness of MB tumor cells in the tissue context. These data thus describe a novel function of MAP4K4 in the control of the PM-associated proteome of tumor cells and identified two downstream effector mechanisms controlling proliferation and invasiveness of MB cells. Graphical abstractc-MET activation upon HGF stimulation induces c-MET internalization and induces downstream MAP4K4 activity. (1) MAP4K4 is required downstream of activated c-MET for the maintenance of surface presentation of CD155 in activated cells. CD155 expression is required for MB cell migration, invasion and proliferation in the tissue context. (2) MAP4K4 is required downstream of activated c-MET to maintain membrane depolarization, possibly by regulating the surface localization of several ion channels and transporters. (3) MAP4K4 is required downstream of activated c-MET cause PM-proximal localization of FEME effector CIP4, FBP17 and CIN85. The FEME effector endophilin A is necessary for MB cell migration, invasion and dissemination.

cell biology↗

bioRxiv2021

Disturbed retinoid metabolism upon loss of rlbp1a impairs cone function and leads to subretinal lipid deposits and photoreceptor degeneration in the zebrafish retina

The RLBP1 gene encodes the 36 kDa cellular retinaldehyde binding protein, CRALBP, a soluble retinoid carrier, in the visual cycle of the eyes. Mutations in RLBP1 are associated with recessively inherited clinical phenotypes, including Bothnia dystrophy, retinitis pigmentosa, retinitis punctata albescens, fundus albipunctatus, and Newfoundland rod-cone dystrophy. However, the etiology of these retinal disorders is not well understood. Here, we generated homologous zebrafish models to bridge this knowledge gap. Duplication of the rlbp1 gene in zebrafish and cell-specific expression of the paralogs rlbp1a in the retinal pigment epithelium and rlbp1b in Muller glial cells allowed us to create intrinsically cell type-specific knockout fish lines. Using rlbp1a and rlbp1b single and double mutants, we investigated the pathological effects on visual function. Our analyses revealed that rlbp1a was essential for cone photoreceptor function and chromophore metabolism in the fish eyes. rlbp1a mutant fish displayed reduced chromophore levels and attenuated cone photoreceptor responses to light stimuli. They accumulated 11-cis and all-trans-retinyl esters which displayed as enlarged lipid droplets in the RPE reminiscent of the subretinal yellow-white lesions in patients with RLBP1 mutations. During aging, these fish developed retinal thinning and cone and rod photoreceptor dystrophy. In contrast, rlbp1b mutants did not display impaired vision. The double mutant essentially replicated the phenotype of the rlbp1a single mutant. Together, our study showed that the rlbp1a zebrafish mutant recapitulated many features of human blinding diseases caused by RLBP1 mutations and provided novel insights into the pathways for chromophore regeneration of cone photoreceptors. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=82 SRC="FIGDIR/small/448986v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@bd3de5org.highwire.dtl.DTLVardef@2a9420org.highwire.dtl.DTLVardef@162e7f0org.highwire.dtl.DTLVardef@697ee6_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2021

Loss of the glial glutamate transporter eaat2a leads to a combined developmental and epileptic encephalopathy in zebrafish

Astroglial excitatory amino acid transporter 2 (EAAT2, GLT-1, SLC1A2) regulates the duration and extent of neuronal excitation by removing glutamate from the synaptic cleft. Hence, an impairment in EAAT2 function could lead to an imbalanced neural network excitability. Here, we investigated the functional alterations of neuronal and astroglial networks associated with the loss of function in the astroglia predominant eaat2a gene in zebrafish. We observed that eaat2a-/- mutant zebrafish larvae display recurrent spontaneous and light-induced seizures in neurons and astroglia, which coincide with an abrupt increase in extracellular glutamate levels. In stark contrast to this hyperexcitability, basal neuronal and astroglial activity was surprisingly reduced in eaat2a-/- mutant animals, which manifested in decreased overall locomotion. Our results reveal an essential and mechanistic contribution of EAAT2a in balancing brain excitability, and its direct link to epileptic seizures.

neuroscience↗

bioRxiv2018

Differential expression of PKCα and -β in the zebrafish retina

The retina is a complex neural circuit in which visual information is transmitted and processed from light perceiving photoreceptors to projecting retinal ganglion cells. Much of the computational power of the retina rests on signal integrating interneurons, such as bipolar cells in the outer retina. While mammals possess about 10 different bipolar cell types, zebrafish (Danio rerio) has at least six ON-type, seven OFF-type, and four mixed-input bipolar cells. Commercially available antibodies against bovine and human conventional protein kinase C (PKC) and -{beta} are frequently used as markers for retinal ON-bipolar cells in different species, despite the fact that it is not known which bipolar cell subtype(s) they actually label.\n\nMoreover, the expression pattern of the five prkc genes (coding for PKC proteins) has not been systematically determined. While prkcg is not expressed in retinal tissue, the other four prkc (prkcaa, prkcab, prkcba, prkcbb) transcripts were found in different parts of the inner nuclear layer and some as well in the retinal ganglion cell layer.\n\nImmunohistochemical analysis in adult zebrafish retina using PKC and PKC{beta} antibodies showed an overlapping immunolabeling of ON-bipolar cells that are most likely of the BON s6L or RRod type and of the BON s6 type. However, comparison of transcript expression with immunolabling, implies that these antibodies are not specific for one single zebrafish conventional PKC, but rather detect a combination of PKC - and -{beta} variants.

neuroscience↗

bioRxiv2018

Nucleoporin 133 deficiency leads to glomerular damage in zebrafish

Although structural nuclear pore proteins (nucleoporins) are seemingly required in every cell type to assemble a functional nuclear transport machinery, mutations or deregulation of a subset of them have been associated with specific human hereditary diseases. In particular, previous genetic studies of patients with nephrotic syndrome identified mutations in Nup107 that impaired the expression or the localization of its direct partner at nuclear pores, Nup133. In the present study, we characterized the zebrafish nup133 orthologous gene and its expression pattern during larval development. Morpholino-mediated gene knockdown revealed that Nup133 depletion in zebrafish larvae leads to the formation of kidney cysts, a phenotype that can be rescued by co-injection of wild type mRNA. Analysis of different markers for tubular and glomerular development shows that the overall kidney development is not affected by nup133 knockdown. On the other hand, we demonstrate that nup133 is essential for the organization and functional integrity of the pronephric glomerular filtration barrier, as its downregulation results in proteinuria and moderate foot process effacement, mimicking some of the abnormalities typically featured by patients with nephrotic syndrome. These data indicate that nup133 is a new gene required for proper glomerular structure and function in zebrafish.

developmental biology↗