Biology subjects

Janssen, W.

Publications and source records attributed to Janssen, W..

6 recordsLinked to original sources

bioRxiv2026

The Hao-Fountain syndrome gene USP7 restricts neurotropic orthoflavivirus entry through cell intrinsic control of endosomal dynamics

Neurodevelopmental disorders are increasingly associated with immune phenotypes, including autoinflammation, immunodeficiency, and increased susceptibility to severe infection. To determine whether neurodevelopmental disorders-associated genes exert immune functions, we performed an arrayed siRNA screen targeting 28 genes with nonredundant cellular roles and assessed their effects on Zika virus (ZIKV) infection and innate immune pathways. We identified hits that intrinsically restrict ZIKV infection and modulate inflammatory pathways following infection. We further characterized the antiviral activity of the Hao-Fountain syndrome gene USP7, which potently restricts selected neurotropic orthoflaviviruses. USP7 inhibits ZIKV internalization before viral membrane fusion and genome release into the cytoplasm. Because USP7 plays a role in endosomal tubulation and recycling, we investigated whether endosomal recycling pathways restrict ZIKV infection. We identified the USP7-regulated E3 ubiquitin ligase TRIM27, as well as the recycling-associated Rab GTPases RAB11 and RAB35, as potent regulators of ZIKV infection. Infection assays using cell lines expressing pathogenic USP7 variants and primary fibroblasts from individuals with Hao-Fountain syndrome demonstrated that disease-associated USP7 mutations impair its antiviral activity and increase permissivity to ZIKV infection. These findings are consistent with recent case reports of unusually severe viral infection during early life in individuals with Hao-Fountain syndrome. Collectively, our study identifies endosomal recycling pathways as important intrinsic restriction mechanisms against neurotropic orthoflaviviruses and nominates pathogenic USP7 variation as a candidate inborn error of immunity.

microbiology↗

bioRxiv2026

Perfusion quality does not necessarily predict ultrastructural preservation after hyperosmotic brain perfusion

Perfusion fixation is widely used in neuroscience to prepare mammalian brain tissue for histological and ultrastructural analysis. Perfusion protocols are commonly assessed using macroscopic indicators such as gross appearance and neuroimaging, which assess the extent to which perfusate has been distributed throughout the brain. There is a critical need to determine to what extent these metrics can accurately predict high-quality ultrastructural preservation, particularly as new perfusion protocols are developed for connectomics. In this technical report, we describe evidence that these two measures can be decoupled by the addition of dehydrating agents to the perfusate solution. In three human brain donors and one canine brain donor perfused with a fixative solution containing 10% mannitol and 10% polyethylene glycol 35 kDa, macroscopic and radiological indicators of perfusion quality appeared adequate or favorable. However, electron microscopy revealed expanded extracellular space, shrunken cellular processes, and distorted cell membranes, consistent with an osmotic shock artifact resulting from severe hyperosmotic dehydration. Similar ultrastructural artifacts were observed in a canine brain donor perfused with 20% mannitol in 20% neutral buffered formalin without PEG. We compare these ultrastructural findings with findings from previously reported cases perfused with standard neutral buffered formalin without osmotic additives. These findings illustrate a risk of optimizing brain perfusion protocols designed to preserve neural circuitry based on macroscopic or radiological perfusion quality metrics alone, since these metrics can be satisfied while the ultrastructure is severely compromised.

neuroscience↗

bioRxiv2025

Evaluating ultrastructural preservation quality in banked brain tissue

The ultrastructural analysis of postmortem brain tissue can provide important insights into cellular architecture and disease-related changes. For example, connectomics studies offer a powerful emerging approach for understanding neural circuit organization. However, electron microscopy (EM) data is difficult to interpret when the preservation quality is imperfect, which is common in brain banking and may render it unsuitable for certain research applications. One common issue is that EM images of postmortem brain tissue can have an expansion of regions that appear to be made up of extracellular space and/or degraded cellular material, which we call ambiguous interstitial zones. In this study, we report a method to assess whether EM images have ambiguous interstitial zone artifacts in a cohort of 10 postmortem brains with samples from each of the cortex and thalamus. Next, in matched samples from the contralateral hemisphere of the same brains, we evaluate the structural preservation quality of light microscopy images, including immunostaining for cytoskeletal proteins. Through this analysis, we show that on light microscopy, cell membrane morphology can be largely maintained, and neurite trajectory visualized over micrometer distances, even in specimens for which there are ambiguous interstitial zone artifacts on EM. Taken together, our analysis may assist in maximizing the usefulness of donated brain tissue by informing tissue selection and preparation protocols for various research goals.

neuroscience↗

bioRxiv2022

Integrated single-cell (phospho-)protein and RNA detection uncovers phenotypic characteristics of human antibody secreting cells.

Antibody-secreting cells (ASCs) secrete IgM, IgA, or IgG antibodies and are key components of humoral immunity; however, little is known about unique characteristics of the Ig-classes due to limited availability of material and challenges to quantify many intracellular molecular modalities at a single-cell resolution. We combined a method to in vitro differentiate peripheral B-cells into ASCs with integrated multi-omic single-cell sequencing technologies to quantify subclass-specific hallmark surface markers, transcriptional profiles and signaling transduction pathway components. Our approach detected differential expression of plasmablast and plasma cell markers, homing receptors and IL-2, IL-6, JAK/STAT and mTOR signaling activity across Ig-subclasses. Taken together, our integrated multi-omics approach allowed high-resolution phenotypic characterization of single cells in a complex sample of in vitro differentiated human ASCs. Our strategy is expected to further our understanding of human ASCs in healthy and diseased samples and provide a valuable tool to identify novel biomarkers and potential drug targets. TeaserIntegrated single-cell analysis allows tri-modal phenotypic analysis of in-vitro generated human antibody-secreting cells.

immunology↗

bioRxiv2020

Human and mouse transcriptome profiling identifies cross-species homology in pulmonary and lymph node mononuclear phagocytes

The mononuclear phagocyte (MP) system consists of macrophages, monocytes, and dendritic cells (DCs). MP subtypes play distinct functional roles in steady state and inflammatory conditions. Though murine MPs are well characterized, their pulmonary and lymph node (LN) human homologs remain poorly understood. To address this gap, we created a gene expression compendium across 15 distinct human and 9 distinct murine MPs from lung, LN, blood, and spleen. Human blood MPs and murine spleen MPs served as validation datasets, as the human-mouse MP homologs are relatively well-defined in these tissues. In-depth RNA sequencing identified corresponding human-mouse MP subtypes and determined marker genes shared and divergent across between species counterparts. Unexpectedly, at the gene expression level, only 13-23% of the top 1000 marker genes (i.e., genes not shared across species-specific MP subtypes) overlapped in corresponding human-mouse MP counterparts, indicating a need for caution when translating mouse studies to human gene targets and functions. Lastly, CD88 was useful in both species to distinguish macrophage and tissue monocytes from DCs. Our cross-species gene expression compendium serves as a resource for future translational studies to investigate beforehand whether pursuing specific MP subtypes, or genes will prove fruitful.

immunology↗

bioRxiv2019

Orexin signaling in GABAergic lateral habenula neurons modulates aggressive behavior

Heightened aggression is characteristic of multiple neuropsychiatric disorders and can have a wide variety of negative effects on patients, their families, and the public. Recent studies in humans and animals have implicated brain reward circuits in aggression and suggest that, in subsets of aggressive individuals, repeated domination of subordinate social targets is reinforcing. Here, we show that orexin neurons originating from the lateral hypothalamus activate a small population of GABAergic interneurons in the lateral habenula (LHb) via orexin receptor 2 (OxR2) to promote aggression and conditioned place preference (CPP) for aggression-paired contexts. Our study suggests that the orexin system is a potential target for the development of novel therapies aimed at reducing aggressive behaviors and provides the first functional evidence of a local inhibitory circuit within the LHb.

neuroscience↗