Biology subjects

Hans, S.

Publications and source records attributed to Hans, S..

9 recordsLinked to original sources

bioRxiv2026

Aquamin a marine derived multi mineral attenuates toll like receptor mediated inflammatory responses in macrophages.

Toll-like receptors (TLRs) play a central role in innate immune responses through recognition of pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). Activation of TLRs leads to the induction of inflammatory cytokines via MyD88- and TRIF-dependent signaling pathways. Aquamin, a multi-mineral supplement derived from the marine red algae Lithothamnion, is known for its anti-inflammatory properties. In this study, we demonstrate that Aquamin dose-dependently inhibits lipopolysaccharide (LPS)-induced production of pro-inflammatory cytokines (TNF-, IL-6, IL-1{beta}) and chemokines in both human peripheral blood mononuclear cells (hPBMCs) and murine bone marrow-derived macrophages (mBMDMs), without causing cytotoxicity. Mechanistic studies demonstrate that Aquamin specifically suppressed TRIF dependent IRF3 activation downstream of TLR3 and TLR4. These findings support Aquamin as a promising agent for use as an intervention in counteracting inflammatory diseases states where TLR signalling is implicated.

immunology↗

bioRxiv2024

Blind but alive - congenital loss of atoh7 disrupts the visual system of adult zebrafish.

1PurposeVision is the predominant sense in most animal species. Loss of vision can be caused by a multitude of factors resulting in anatomical as well as behavioral changes. In mice and zebrafish, atoh7 mutants are completely blind as they fail to generate retinal ganglion cells during development. In contrast to mice, raising blind zebrafish to adulthood is challenging and this important model is currently missing in the field. Here, we report the phenotype of homozygous mutant adult zebrafish atoh7 mutants that have been raised using adjusted feeding and holding conditions. MethodsThe phenotype of adult mutants was characterized using classical histology and immunohistochemistry as well as optical coherence tomography. In addition, the optokinetic response was characterized. ResultsAdult atoh7 mutants display dark body pigmentation and significantly reduced body length. They fail to form retinal ganglion cells, the resulting nerve fiber layer as well as the optic nerve, and consequently behave completely blindly. In contrast, increased amounts of other retinal neurons and Muller glia are formed. In addition, the optic tectum is anatomically reduced in size, presumably due to the missing retinal input. ConlusionsTaken together, we provide a comprehensive characterization of a completely blind adult zebrafish mutant with focus on retinal and tectal morphology, as a useful model for glaucoma and optic nerve aplasia.

neuroscience↗

bioRxiv2023

Successful regeneration of the adult zebrafish retina is dependent on inflammatory signaling

Inflammation can lead to persistent and irreversible loss of retinal neurons and photoreceptors in mammalian vertebrates. In contrast, in the adult zebrafish brain, acute neural inflammation is both necessary and sufficient to stimulate regeneration of neurons. Here, we report on the critical, positive role of the immune system to support retina regeneration in adult zebrafish. After sterile, ablation of photoreceptors by phototoxicity, we find rapid response of tissue-resident microglia and neutrophils, which returns to homeostatic levels within 14 days post lesion. Pharmacological or genetic impairment of immune cell reactivity results in a reduced Muller glia stem cell response, seen as decreased reactive proliferation, and a strikingly reduced number of regenerated cells from them, including photoreceptors. Conversely, injection of the immune stimulators flagellin, zymosan, or M-CSF into the vitreous of the eye, in spite of the absence of a retinal lesion, leads to a robust proliferation response and the up-regulation of regeneration-associated marker genes in Muller glia. Our results suggest that neuroinflammation is a necessary and sufficient driver for retinal regeneration in the adult zebrafish retina.

developmental biology↗

bioRxiv2023

scRNAseq unravels the transcriptional network underlying zebrafish retina regeneration

In the lesioned zebrafish retina, Muller glia produce multipotent retinal progenitors that generate all retinal neurons, replacing lost cell types. To study the molecular mechanisms linking Muller glia reactivity to progenitor production and neuronal differentiation, we used single cell RNA sequencing of Muller glia, progenitors and regenerated progeny from uninjured and light-lesioned retinae. We discover an injury-induced Muller glia differentiation trajectory that leads into a cell population with a hybrid identity expressing marker genes of Muller glia and progenitors. A glial self-renewal and a neurogenic trajectory depart from the hybrid cell population. We further observe that neurogenic progenitors progressively differentiate to generate retinal ganglion cells first and bipolar cells last, similar to the events observed during retinal development. Our work provides a comprehensive description of Muller glia and progenitor transcriptional changes and fate decisions in the regenerating retina, which are key to tailor cell differentiation and replacement therapies for retinal dystrophies in humans.

developmental biology↗

bioRxiv2022

Real-time monitoring of endogenous Fgf8a gradient attests to its role as a morphogen during zebrafish gastrulation

Morphogen gradients impart positional information to cells in a homogenous tissue field. Fgf8a, a highly conserved growth factor, has been proposed to act as a morphogen during zebrafish gastrulation. However, technical limitations have so far prevented direct visualization of the endogenous Fgf8a gradient and confirmation of its morphogenic activity. Here, we monitored Fgf8a propagation in the developing neural plate using a CRISPR/Cas9-mediated EGFP knock-in at the endogenous fgf8a locus. By combining sensitive imaging platforms with single-molecule Fluorescence Correlation Spectroscopy (FCS), we demonstrate that Fgf8a, produced at the embryonic margin, propagates by free diffusion through the extracellular space and forms a graded distribution towards the animal pole. Overlaying the Fgf8a gradient curve with expression profiles of its downstream targets determines the precise input-output relationship of Fgf8a mediated patterning. Manipulation of the Fgf8a input alters the signaling outcome, thereby establishing Fgf8a as a bona fide morphogen during zebrafish gastrulation. Furthermore, using diffusion-hindered versions of Fgf8a, we demonstrate that extracellular diffusion of the protein from the source is critical for it to achieve its morphogenic potential.

developmental biology↗

bioRxiv2022

Vision-related convergent gene losses reveal SERPINE3's unknown role in the eye

Despite decades of research, knowledge about the genes that are important for development and function of the mammalian eye and are involved in human eye disorders remains incomplete. During mammalian evolution, mammals that naturally exhibit poor vision or regressive eye phenotypes have independently lost many eye-related genes. This provides an opportunity to predict novel eye-related genes based on specific evolutionary gene loss signatures. Building on these observations, we performed a genome-wide screen across 49 mammals for functionally uncharacterized genes that are preferentially lost in species exhibiting lower visual acuity values. The screen uncovered several genes, including SERPINE3, a putative serine proteinase inhibitor. A detailed investigation of 381 additional mammals revealed that SERPINE3 is independently lost in 18 lineages that typically do not primarily rely on vision, predicting a vision-related function for this gene. To test this, we show that SERPINE3 has the highest expression in eyes of zebrafish and mouse. In the zebrafish retina, serpine3 is expressed in Mueller glia cells, a cell type essential for survival and maintenance of the retina. A CRISPR-mediated knockout of serpine3 in zebrafish resulted in alterations in eye shape and defects in retinal layering. Furthermore, two human polymorphisms that are in linkage with SERPINE3 are associated with eye-related traits. Together, these results suggest that SERPINE3 has a role in vertebrate eyes. More generally, by integrating comparative genomics with experiments in model organisms, we show that screens for specific phenotype-associated gene signatures can predict functions of uncharacterized genes.

evolutionary biology↗

bioRxiv2019

Cell-fate plasticity, adhesion and cell sorting complementarily establish a sharp midbrain-hindbrain boundary

The formation and maintenance of sharp boundaries between groups of cells play a vital role during embryonic development as they serve to compartmentalize cells with similar fates. Some of these boundaries also act as organizers, with the ability to induce specific cell fates and morphogenesis in the surrounding cells. The midbrain-hindbrain boundary (MHB) is an example of such an organizer that also acts as a lineage restriction boundary that prevents the intermingling of cells with different developmental fates. However, the mechanisms underlying the lineage restriction process remain unclear. Here, using a combination of novel fluorescent knock-in reporters, live imaging, Cre/lox-mediated lineage tracing, atomic force microscopy-based cell adhesion assays, and mutant analysis, we analyze the process of lineage restriction at the MHB and provide mechanistic details. Specifically, we show that lineage restriction occurs by the end of gastrulation, and that the subsequent formation of sharp gene expression boundaries in the developing MHB occur through complementary mechanisms, namely cell-fate plasticity and cell sorting. Further, we show that cell sorting at the MHB involves differential adhesion among midbrain and hindbrain cells that is mediated by N-cadherin and Eph-Ephrin signaling.

developmental biology↗

bioRxiv2018

HPV detection and genotyping of FFPE head and neck cancer biopsies by molecular testing to address new oropharyngeal squamous cell carcinoma classification based on HPV status

Recently, both the WHO/IARC (World Health Organisation/International Agency for Research on Cancer) and the American Joint Committee on Cancer (AJCC) have classified the oropharyngeal squamous cell carcinoma (OPSCC) on the basis of HPV status. For this purpose, the WHO/IARC recommended direct molecular HPV testing. In practice, formalin-fixed, paraffin-embedded (FFPE) biopsy specimens are frequently the only available samples. We herein compared in parallel two commercially available molecular assays that were firstly designed for cervical HPV detection and genotyping: Inno-Lipa(R) HPV genotyping extra II assay (Fujirebio, Gent, Belgium) (IL) and AnyplexTM II HPV 28 (Seegene, Seoul, South Korea) (AP28).\n\nBoth assays were carried out on the same DNA extracts obtained from prospectively collected FFPE biopsies from OPSCC origin and results were compared.\n\nA total of 55 samples were tested. By IL assay, chosen as reference assay, 27 (49.1%) biopsies were positive for HPV16, 10 (18.2%) were positive for HPV but negative for HPV16, and 18 (32.7%) were negative for HPV. A valid result with AP28 was obtained for 51 biopsy samples (92.7%). Among 37 HPV-positive samples by IL, 33 (89.2%) were positive by AP28. The agreement between both assays was good (Cohens {kappa} = 0.78). Among the six discrepancies between assays, always associated with low HPV16 viral load, four biopsies positive for HPV16 by IL could not be detected by AP28.\n\nTaken together, these observations demonstrate that both assays could be used in routine for HPV detection and genotyping on FFPE-biopsy samples of head and neck tumour.

molecular biology↗

bioRxiv2017

Loss Of lrrk2 Impairs Cell Proliferation And Neuronal Regeneration In The Zebrafish Brain

LRRK2 mutations are a major cause of Parkinsons disease. Pathogenicity of LRRK2 loss-of-function is controversial, as knockout in rodents reportedly induces no brain-specific effects and knockdown studies in zebrafish are conflicting. Here we show that CRISPR/Cas9-engineered deletion of the ~60-kbp-long zebrafish lrrk2 locus elicits a pleomorphic, albeit transient brain phenotype in maternal-zygotic mutants (mzLrrk2). Intriguingly, 11-month-old mzLrrk2 adults display increased dopamine and serotonin catabolism. Additionally, we find decreased mitosis in the larval brain and reduced stab injury-induced neuronal regeneration in the adult telencephalon. Finally, hypokinesia associates with loss of lrrk2 in larvae. Our results demonstrate that lrrk2 knockout has an early neurodevelopmental effect, and leads to perturbed dopamine and serotonin catabolism in a LRRK2 knockout. We propose mzLrrk2 zebrafish as a valuable tool to study LRRK2 loss-of-function in vivo, and provide a link between LRRK2 and the control of basal cell proliferation in the brain that may become potentially critical upon challenges like brain injury.

neuroscience↗