Biology subjects

Washer, S. J.

Publications and source records attributed to Washer, S. J..

6 recordsLinked to original sources

bioRxiv2025

Tracking tau and cellular responses in human iPSC-microglia from uptake to seedable secretion in extracellular vesicles

The templated spread of tau aggregates in tauopathies has been attributed to neuron-to- neuron spread, but microglia have also been implicated through mouse studies. Here we examine in detail the uptake, processing, release and seeding of tau using human iPS- derived microglia (iMGL). We show that tau is taken up by iMGL via LRP1 and heparan sulfate proteoglycans, with a role for LRRK2 in LRP1 trafficking, and that phagocytosed fibrils can escape into the cytoplasm. Monomeric tau has minimal effects on iMGL, but recombinant or brain-derived tau fibrils induce a shift towards chemokine and interferon response subtypes, alongside downregulation of homeostatic and MHC genes. Endogenous tau protein is undetectable in iMGL, and monomeric internalised tau is digested to completion, but fibrillar tau is more resistant to degradation and becomes phosphorylated on two specific residues. Finally, fibrillar tau is released by iMGL, visualized within extracellular vesicles by cryo-EM, and can seed tau aggregation in downstream neurons.

cell biology↗

bioRxiv2024

Unbiased preclinical phenotyping reveals neuroprotective properties of pioglitazone

Animal models are essential for assessing the preclinical efficacy of candidate drugs, but animal data often fails to replicate in human clinical trials. This translational gulf is due in part to the use of models that do not accurately replicate human disease processes and phenotyping strategies that do not capture sensitive, disease-relevant measures. To address these challenges with the aim of validating candidate neuroprotective drugs, we combined a mouse prion (RML scrapie) model that recapitulates the key common features of human neurodegenerative disease including bona fide neuronal loss, with unbiased and machine learning-assisted behavioural phenotyping. We found that this approach measured subtle, stereotyped, and progressive changes in motor behaviour over the disease time course that correlated with the earliest detectable histopathological changes in the mouse brain. To validate the utility of this model system, we tested whether the anti-diabetic drug pioglitazone could slow prion disease progression. Pioglitazone crosses the blood-brain-barrier and has been shown to reduce neurodegenerative disease severity in other mouse models. We found that in addition to significantly slowing the emergence of early-stage clinical signs of neurodegeneration, pioglitazone significantly improved motor coordination throughout the disease time course and reduced neuronal endoplasmic reticulum stress. Together, these findings suggest that pioglitazone could have neuroprotective properties in humans, confirm the utility of the scrapie mouse model of neurodegeneration, and provide generalisable experimental and analysis methods for the generation of data-rich behavioural data to accelerate and improve preclinical validation.

neuroscience↗

bioRxiv2024

ONE-STEP tagging: a versatile method for rapid site-specificintegration by simultaneous reagent delivery

We present a novel, versatile genome editing method termed ONE-STEP tagging, which combines CRISPR-Cas9-mediated targeting with Bxb1 integrase-based site-specific integration for efficient, precise, and scalable protein tagging. Applied in hiPSCs, cancer cells, and primary T cells, this system enables rapid generation of endogenously tagged cell lines. By enhancing the nuclear localization signal (NLS) of the catalytically superior eeBxb1 integrase and co-delivering a DNA-PK inhibitor (AZD-7648), we achieved up to [~]90% integration efficiency at the ACTR10 locus. ONE-STEP tagging is robust across diverse loci and cell types and supports large DNA cargo integration, with efficiencies reaching 16.6% for a 14.4 kb construct. The method also enables multiplexed tagging of multiple proteins within the same cell and allows simultaneous CRISPR-based editing at secondary loci, such as gene knockouts or homology-directed repair (HDR) insertions. Importantly, we demonstrate successful application in primary T cells by targeting the T cell receptor (TCR) locus while simultaneously knocking out B2M, a key step toward generating immune-evasive, off-the-shelf CAR-T cells. Additionally, we introduce a dual-cassette version of the method compatible with universal donor plasmids, allowing use of entirely off-the-shelf reagents. Together, these advances establish ONE-STEP tagging as a powerful tool for both basic and therapeutic genome engineering.

molecular biology↗

bioRxiv2023

Proximity proteomics reveals UCH-L1 as an essential regulator of NLRP3 mediated IL-1β production in human macrophages and microglia

Activation of the NACHT, LRR family pyrin domain containing 3 (NLRP3) inflammasome complex is an essential innate immune signalling mechanism. To reveal how human NLRP3 inflammasome assembly and activation are controlled, in particular by components of the ubiquitin system, proximity labelling, affinity purification and RNAi screening approaches were performed. Our study provides an intricate time-resolved molecular map of different phases of NLRP3 inflammasome activation. Also, we show that ubiquitin C-terminal hydrolase 1 (UCH-L1) interacts with the NACHT domain of NLRP3. Downregulation of UCH-L1 decreases pro-IL-1{beta} levels. UCH-L1 chemical inhibition with small molecules interfered with NLRP3 puncta formation and ASC oligomerization, leading to altered IL-1{beta} cleavage and secretion, particularly in microglia cells, which exhibited elevated UCH-L1 expression as compared to monocytes/macrophages. Altogether, we profiled NLRP3 inflammasome activation dynamics and highlight UCH-L1 as an important modulator of NLRP3-mediated IL-1{beta} production, suggesting that a pharmacological inhibitor of UCH-L1 may decrease inflammation-associated pathologies.

biochemistry↗

bioRxiv2022

Single-cell transcriptomics defines an improved, validated monoculture protocol for differentiation of human iPSCs to microglia

There is increasing genetic evidence for the role of microglia in neurodegenerative diseases, including Alzheimers, Parkinsons, and motor neuron disease. Therefore, there is a need to generate authentic in vitro models to study human microglial physiology. Various methods have been developed using human induced Pluripotent Stem Cells (iPSC) to generate microglia, however, systematic approaches to identify which media components are actually essential for functional microglia are mostly lacking. Here, we systematically assess medium components, coatings, and growth factors required for iPSC differentiation to microglia. Using single-cell RNA sequencing, qPCR, and functional assays, with validation across two labs, we have identified several medium components from previous protocols that are redundant and do not contribute to microglial identity. We provide an optimised, defined medium which produces both transcriptionally and functionally relevant microglia for modelling microglial physiology in neuroinflammation and for drug discovery.

immunology↗

bioRxiv2019

An alternatively spliced zebrafish jnk1a transcript has an essential and non-redundant role in development of the first heart field derived proximal ventricular chamber.

Alternative splicing is a ubiquitous mechanism for producing different mRNA species from a single gene, resulting in proteomic diversity. Despite potential for regulating embryogenesis, its developmental role remains under-investigated. The Jun kinase (Jnk) genes, considered downstream effectors of the non-canonical Wnt planar cell polarity pathway, utilise extensive and evolutionarily-conserved alternative splicing. Although many PCP members are associated with heart malformation, the role of Jnk genes in cardiac development, and specifically which alternatively spliced transcripts orchestrate these processes, remain unknown. In this study we exploit the jnk1 duplication and subspecialisation found in zebrafish to reveal an essential and non-redundant requirement for jnk1a in cardiac development. We characterise alternatively spliced jnk1a/jnk1b transcripts and demonstrate that hypoplasia of the proximal ventricular component, which corresponds to human hypoplastic left ventricle, can only be rescued by the jnk1a Ex7 Lg transcript. These studies highlight the importance of Jnk signalling and alternative splicing in heart development

developmental biology↗