Biology subjects

Johnson, S.

Publications and source records attributed to Johnson, S..

At least 55 records · Page 3Linked to original sources

bioRxiv2024

Orchids, hawkmoths and Darwin revisited: How adaptation to pollination by hawkmoths spurred the speciation of Old and New World angraecoids

Specialised pollination has often been proposed as a major driver of the unrivalled diversification of angiosperms. With its unparalleled variation in flower depth, ranging from spurless to 40 cm spurred flowers pollinated by hawkmoths, angraecoid orchids (Angraecinae) provide unique opportunities to reveal the impact of floral specialisation on diversification rates in the Afrotropics and Neotropics. We compiled floral characters for 327 angraecoid species, and assigned these species to newly formalised floral syndrome categories calibrated against pollination case studies. We then estimated ancestral character states and state-dependent speciation rates using the latest time-calibrated phylogeny of angraecoids. We found that white flowers consistent with micro-sphingophily (2 cm[≥] spurs <8.7 cm), macro-sphingophily (8.7 cm[≥] spurs <18.6 cm) and mega-sphingophily (spurs [≥]18.6 cm) evolved repeatedly in angraecoids, and are ancestral in some non-sphingophilous clades. Reversals to non-sphingophily and pigmented flowers suggest higher evolutionary lability of these traits than what is traditionally thought. Increasing floral specialisation with long spurs does not seem to enhance angraecoid orchids speciation rates, since micro-sphingophily appears to be associated with the highest speciation rates. An abundance of short-proboscid hawkmoths in Madagascar, as an ecological opportunity, may have accelerated the speciation of micro-sphingophilous taxa.

evolutionary biology↗

bioRxiv2024

Gut Microbiome Signatures During Acute Infection Predict Long COVID

Long COVID (LC), manifests in 10-30% of non-hospitalized individuals post-SARS-CoV-2 infection leading to significant morbidity. The predictive role of gut microbiome composition during acute infection in the development of LC is not well understood, partly due to the heterogeneous nature of disease. We conducted a longitudinal study of 799 outpatients tested for SARS-CoV-2 (380 positive, 419 negative) and found that individuals who later developed LC harbored distinct gut microbiome compositions during acute infection, compared with both SARS-CoV-2-positive individuals who did not develop LC and negative controls with similar symptomatology. However, the temporal changes in gut microbiome composition between the infectious (0-1 month) and post-infectious (1-2 months) phases was not different between study groups. Using machine learning, we showed that microbiome composition alone more accurately predicted LC than clinical variables. Including clinical data only marginally enhanced this prediction, suggesting that microbiome profiles during acute infection may reflect underlying health status and immune responses thus, help predicting individuals at risk for LC. Finally, we identified four LC symptom clusters, with gastrointestinal and fatigue-only groups most strongly linked to gut microbiome alterations.

genomics↗

bioRxiv2024

Coatomer protein complex I is required for efficient secretion of dengue virus non-structural protein 1

Secreted non-structural protein 1 (sNS1) is an important orthoflavivirus pathogenic factor that can induce vascular leakage; a key symptom of severe dengue disease. Given the role of sNS1 in dengue pathogenesis, defining the molecular mechanisms of NS1 secretion may contribute towards development of NS1-targeting antiviral therapies. To this end, we performed a customised membrane-trafficking siRNA screen to identify human host factors involved in NS1 secretion. Our screen identified COPA, COPB2, and COPG1 as the top-ranking hits. These proteins are three of the seven subunits of the coatomer protein complex I (COPI) that coat transport vesicles that operate within the early secretory pathway, implicating COPI machinery as being involved in NS1 secretion. Validation studies employing host gene knockdown in dengue virus (DENV)-infected cells confirmed that COPI components are required for efficient NS1 secretion but are dispensable for infectious virus egress. Similar reductions in NS1 secretion were observed when COPI components were depleted in cells infected with West Nile virus Kunjin subtype (WNV/KUNV), indicating that the molecular mechanisms exploited to achieve NS1 secretion may be a conserved feature within the Orthoflavivirus genus. Heterologous expression of wildtype and pathogenic COPI variants in DENV NS1-NS5 polyprotein expressing cells resulted in altered NS1 secretion profiles, suggesting that allelic variants and altered expression levels of COPI components may indirectly influence the severity of dengue disease. The identification of COPI components as important determinants of NS1 secretion efficiency may aid in the identification of novel targets for anti-orthoflaviviral therapies. IMPORTANCEOver half of the worlds population is at risk of infection with mosquito-borne pathogenic orthoflaviviruses such as DENV. Although the secreted form of the viral NS1 protein has been identified as a major determinant of the pathogenic effects of DENV and related orthoflaviviruses, the exact mechanisms involved in NS1 secretion are poorly understood. Here we interrogated host factors involved in secretion of NS1 from infected cells using a customised membrane trafficking siRNA screen. This revealed 3 components of the COPI complex that regulates vesicular transport in the early secretory pathway as important factors in NS1 secretion. The involvement of COPI components in NS1 secretion was further validated using wildtype DENV and WNV/KUNV infection, overexpression approaches and chemical inhibition studies. Together, this study demonstrates the importance of COPI machinery in NS1 secretion and suggests that exploitation of this machinery in NS1 secretion may represent a future target of antiviral drug development.

cell biology↗

bioRxiv2024

Functional impact of the hyperduplication genomophenotype in high copy number endometrial cancer

High copy number endometrial cancers (HCNEC) are dominated by excessive duplications scattered across the genome, termed here as the HyperDuplication GenomoPhenotype (HDGP). Although correlated with cancer progression, its biological significance and implications for therapy have not yet been established. We identified locations and sizes of duplications in 171 endometrial cancer cases and designated 71 HCNEC cases as HDGP. We also investigated the response to the pan-ERBB inhibitor afatinib in a subset of HDGP-EC cases with ERBB2/ERBB3 duplications using a patient-derived three-dimensional culture model. Our analysis demonstrates that beyond tandem duplications there is a more general pattern involving coordinated duplication of multiple distant regions of the genome, demonstrating preferential selectivity to over-expressed potential oncogenes within a broad network. This suggests that HDGP increases tumor fitness and resistance to therapy by perturbing important gene networks in concert rather than only driver genes, suggesting a mechanistic basis for the ineffectiveness of targeted drugs in these patients and highlighting the need for combination therapies in these highly aggressive cases.

genomics↗

bioRxiv2024

TRAMP assembly alters the conformation and RNA binding of Mtr4 and Trf4-Air2

The TRAMP complex contains two enzymatic activities essential for RNA processing upstream of the nuclear exosome. Within TRAMP, RNA is 3 polyadenylated by a sub-complex of Trf4/5 and Air1/2 and unwound 3 to 5 by Mtr4, a DExH helicase. The molecular mechanisms of TRAMP assembly and RNA shuffling between the two TRAMP catalytic sites are poorly understood. Here, we report solution hydrogen-deuterium exchange data with thermodynamic and functional assays to uncover these mechanisms for yeast TRAMP with Trf4 and Air2 homologs. We show that TRAMP assembly constrains RNA-recognition motifs that are peripheral to catalytic sites. These include the Mtr4 Arch and Air2 zinc knuckles 1, 2, and 3. While the Air2 Arch-interacting motif likely constrains the Mtr4 Arch via transient interactions, these do not fully account for the importance of the Mtr4 Arch in TRAMP assembly. We further show that tRNA binding by single active-site subunits, Mtr4 and Trf4-Air2, differs from the double active-site TRAMP. TRAMP has reduced tRNA binding on the Mtr4 Fist and RecA2 domains, offset by increased tRNA binding on Air2 zinc knuckles 2 and 3. Competition between these RNA-binding sites may drive tRNA transfer between TRAMP subunits. We identify dynamic changes upon TRAMP assembly and RNA-recognition motifs that transfer RNA between TRAMP catalytic sites.

biochemistry↗

bioRxiv2024

γ-aminobutyric acid receptor B signaling drives glioblastoma in females in an immune-dependent manner

Sex differences in immune responses impact cancer outcomes and treatment response, including in glioblastoma (GBM). However, host factors underlying sex specific immune-cancer interactions are poorly understood. Here, we identify the neurotransmitter {gamma}-aminobutyric acid (GABA) as a driver of GBM-promoting immune response in females. We demonstrated that GABA receptor B (GABBR) signaling enhances L-Arginine metabolism and nitric oxide synthase 2 (NOS2) expression in female granulocytic myeloid-derived suppressor cells (gMDSCs). GABBR agonist and GABA analog promoted GBM growth in females in an immune-dependent manner, while GABBR inhibition reduces gMDSC NOS2 production and extends survival only in females. Furthermore, female GBM patients have enriched GABA transcriptional signatures compared to males, and the use of GABA analogs in GBM patients is associated with worse short-term outcomes only in females. Collectively, these results highlight that GABA modulates anti-tumor immune response in a sex-specific manner, supporting future assessment of GABA pathway inhibitors as part of immunotherapy approaches.

cancer biology↗

bioRxiv2024

A new avian feeding mechanism: Nectar suction by sunbirds

Nectarivory has independently evolved many times among birds, yet little is known about the diversity of feeding mechanisms that enable specialized taxa to efficiently collect this energyrich resource. Multiple avian groups have converged on evolving elongated bills and tube-like tongues adapted for nectar extraction. Old World sunbirds (family Nectariniidae) stand out as having the greatest degree of convergence in bill and tongue morphology with the well-studied and highly-specialized New World hummingbirds (family Trochilidae) which fill their tongues via elastic filling. However, using museum specimens, high-speed video, and fluid modeling, we show that sunbirds use a previously undescribed and unique drinking mechanism not found in any other animal: intralingual suction through the inside of hollow tubular tongues, a remarkable feat for animals without lips or cheeks.

biophysics↗

bioRxiv2024

Genotypic and phenotypic characterization of Enterococcus faecalis isolates from periprosthetic joint infections

Over 2.5 million prosthetic joint implantation surgeries occur annually in the United States. Periprosthetic joint infections (PJIs), though occurring in only 1-2% of patients receiving replacement joints, are challenging to diagnose and treat and are associated with significant morbidity. The Gram-positive bacterium Enterococcus faecalis, which can be highly antibiotic resistant and is a robust biofilm producer on indwelling medical devices, accounts for 2-11% of PJIs. E. faecalis PJIs are understudied compared to those caused by other pathogens, such as Staphylococcus aureus. This motivates the need to generate a comprehensive understanding of E. faecalis PJIs to guide future treatments for these infections. To address this, we describe a panel of E. faecalis strains isolated from the surface of prosthetic joints in a cohort of individuals treated at Mayo Clinic in Rochester, MN. Here, we present the first complete genome assemblage of E. faecalis PJI isolates. Comparative genomics shows differences in genome size, virulence factors, antimicrobial resistance genes, plasmids, and prophages, underscoring the genetic diversity of these strains. These isolates have strain-specific differences in in vitro biofilm biomass, biofilm burden, and biofilm morphology. We measured robust changes in biofilm architecture and aggregation for all isolates when grown in simulated synovial fluid (SSF). Lastly, we evaluated antibiotic efficacy of these isolates and found strain specific changes across all strains when grown in SSF. Results of this study highlight the existence of genetic and phenotypic heterogeneity among E. faecalis PJI isolates which will provide valuable insight and resources for future E. faecalis PJI research. ImportancePeriprosthetic joint infections (PJIs) affect [~]1-2% of those who undergo joint replacement surgery. Enterococcus faecalis is a Gram-positive opportunistic pathogen that causes [~]10% of PJIs in the United States each year, but our understanding of how and why E. faecalis causes PJIs is limited. E. faecalis infections are typically biofilm associated and can be difficult to clear with antibiotic therapy. Here, we provide complete genomes for four E. faecalis PJI isolates from the Mayo Clinic. These isolates have strain-specific differences in biofilm formation, aggregation, and antibiotic susceptibility in simulated synovial fluid. These results provide important insight into genomic and phenotypic features of E. faecalis isolates from PJI.

microbiology↗

bioRxiv2023

Oblique Line Scan Illumination Enables Expansive, Accurate and Sensitive Single Protein Measurements in Solution and in Living Cells

Single-molecule localization microscopy (SMLM) techniques, such as single-molecule tracking (SMT), enable in situ measurements in cells from which data-rich metrics can be extracted. SMT has been successfully applied to a variety of biological questions and model systems, aiming to unravel the spatiotemporal regulation of molecular mechanisms that govern protein function, downstream pathway effects, and cellular function. While powerful, SMLM often suffers from low throughput and illumination inhomogeneity, along with microscope and user-induced technical biases. Due to technical limitations in scaling SMLM techniques, a tradeoff between spatiotemporal resolution and throughput has been made historically, restricting broad application of these technologies. Here we address these limitations using Oblique Line Scan (OLS), a robust single-objective light-sheet based illumination and detection modality that achieves nanoscale spatial resolution and sub-millisecond temporal resolution across a 250 x 190 m field of view. We demonstrate OLS-enabled SMT on Halo-Tagged proteins in living cells capturing protein motion up to 14 m2 /s. By exploiting the adaptability of the acquisition frame rate and the improved rejection of out of focus light, we extend the utility of OLS beyond cellular compartments with in-solution SMT (isSMT) for single-molecule measurement of ligand-protein interactions and disruption of protein-protein interactions (PPI). We illustrate the versatility of OLS by showcasing two-color SMT, STORM, and single molecule fluorescence recovery after photobleaching (FRAP). OLS expands the range of SMLM applications and paves the way for robust, high-throughput single-molecule investigations of protein dynamics required for drug screening and systems biology studies, both in cells and in solution.

biophysics↗

bioRxiv2023

Tumor cell-derived spermidine promotes a pro-tumorigenic immune microenvironment in glioblastoma via CD8+ T cell inhibition

The glioblastoma microenvironment is enriched in immunosuppressive factors that potently interfere with the function of cytotoxic T lymphocytes. Cancer cells can directly impact the immune system, but the mechanisms driving these interactions are not completely clear. Here we demonstrate that the polyamine metabolite spermidine is elevated in the glioblastoma tumor microenvironment. Exogenous administration of spermidine drives tumor aggressiveness in an immune-dependent manner in pre-clinical mouse models via reduction of CD8+ T cell frequency and phenotype. Knockdown of ornithine decarboxylase, the rate-limiting enzyme in spermidine synthesis, did not impact cancer cell growth in vitro but did result in extended survival. Furthermore, glioblastoma patients with a more favorable outcome had a significant reduction in spermidine compared to patients with a poor prognosis. Our results demonstrate that spermidine functions as a cancer cell-derived metabolite that drives tumor progression by reducing CD8+T cell number and function.

cancer biology↗

bioRxiv2023

Multiple Intermediates in the Detergent-Induced Fusion of Lipid Vesicles

Detergent-induced vesicle interactions, critical for applications including virus inactivation, varies according to the detergent type and membrane composition, but the underlying mechanistic details remain underexplored. Here, we use a lipid mixing assay based on Forster resonance energy transfer (FRET), and single-vesicle characterization approaches to identify that sub-micron sized vesicles are induced to fuse by the non-ionic detergent Triton-X 100. We demonstrate that the process is a multi-step mechanism, characterized by discrete values of FRET efficiency between membrane-embedded fluorophores, and involves permeabilization, vesicle docking, hemi-fusion and full lipid mixing at sub-solubilizing detergent concentrations. We also dissect the kinetics of vesicle fusion to surface-tethered vesicles using a label-free quartz-crystal microbalance with dissipation monitoring approach, opening a platform for biotechnology applications. The presented strategies provide mechanistic insight into the dynamics of vesicle fusion and have implications for applications including drug delivery and sensor development where transport and manipulation of encapsulated cargo is essential.

biophysics↗

bioRxiv2023

No general effects of advancing male age on ejaculates: a meta-analysis across the animal kingdom

Senescence, the deterioration of organismal function with advancing age, is a puzzling biological phenomenon. While actuarial senescence (i.e., age-dependent increases in mortality rates) is well described across some taxa, reproductive senescence (i.e. age- dependent declines in reproduction) is less understood, especially in males, with mixed patterns reported across studies. To examine the evidence for male reproductive senescence, we investigated how advancing male age affects ejaculate traits across non-human animals via a meta-analysis yielding 1814 effect sizes from 379 studies. We found no evidence for a general pattern of reproductive senescence. Instead, we found high heterogeneity for how reproduction changes with male age across animals. Some of this heterogeneity (>10%) was associated with biological factors. For example, there were taxonomical differences for some ejaculate traits -- sperm motility declined with male age in lab rodents and fish, whereas ejaculate size improved with male age in bulls, fish, and insects. Some methodological factors were also important in explaining this heterogeneity: studies sampling a larger proportion of a species lifespan were more likely to detect senescence in ejaculate traits, emphasising the need to examine the full life cycle of species to document senescence. Contrary to predictions, we reveal that the evidence for senescence in ejaculate traits is sporadic. Our findings will help generate novel hypotheses and identify more effective methodological approaches for studying male reproductive senescence.

evolutionary biology↗

bioRxiv2023

The impact of paediatric epilepsy and co-occurring neurodevelopmental disorders on functional brain networks in wake and sleep

Epilepsy is one of the most common neurological disorders in children. Diagnosing epilepsy in children can be very challenging, especially as it often coexists with neurodevelopmental conditions like autism and ADHD. Functional brain networks obtained from neuroimaging and electrophysiological data in wakefulness and sleep have been shown to contain signatures of neurological disorders, and can potentially support the diagnosis and management of co-occurring neurodevelopmental conditions. In this work, we use electroencephalography (EEG) recordings from children, in restful wakefulness and sleep, to extract functional connectivity networks in different frequency bands. We explore the relationship of these networks with epilepsy diagnosis and with measures of neurodevelopmental traits, obtained from questionnaires used as screening tools for autism and ADHD. We explore differences in network markers between children with and without epilepsy in wake and sleep, and quantify the correlation between such markers and measures of neurodevelopmental traits. Our findings highlight the importance of considering the interplay between epilepsy and neurodevelopmental traits when exploring network markers of epilepsy.

neuroscience↗

bioRxiv2022

Beyond consensus sequence: a quantitative scheme for inferring transmission using deep sequencing in a bacterial transmission model

Genomic surveillance provides a data source complementary to contact tracing to resolve putative transmission chains. However, the role of within-host diversity in transmission is understudied due to a lack of experimental and clinical datasets that capture within-host diversity in both donors and recipients. Here, we assess the utility of deep-sequenced genomic surveillance within a mouse transmission model where the gastrointestinal pathogen Citrobacter rodentium was controllably spread during co-housing of infected and naive animals. We observed that within-host variants were maintained over multiple transmission steps until fixation or elimination. We present a model for inferring the likelihood that a given pair of samples are linked by transmission, by comparing the allelic frequency at variant genomic loci. Our data affirm that within-host single nucleotide variants (iSNVs) can repeatedly pass from donor to recipient along the transmission chain, and the mere sharing of iSNVs between different transmission pairs offers limited confidence in identifying a transmission pair. Beyond the presence and absence of within-host variants, we show that differences arising in the relative abundance of iSNVs can infer transmission pairs with high precision. An important component of our approach is that the inference is based solely on sequence data, without incorporating epidemiological or demographic data for context. Our model, which substantially reduces the number of comparisons a contact tracer needs to consider, may enhance the accuracy of contact tracing and other epidemiological processes, including early detection of emerging transmission clusters.

genomics↗

bioRxiv2022

Prioritizing Annotated miRNAs: Only a Small Percentage are Candidates for Biological Regulation

The potential for miRNAs to regulate gene expression remains controversial. DROSHA initiates the biogenesis of miRNAs while Argonaute (AGO) and TNRC6 proteins form complexes with miRNAs that recognize RNA. Here we investigate the fate of miRNAs in the absence of critical RNAi protein factors. Knockout of DROSHA expression reduced levels of some miRNAs, but not others. Knocking out AGO proteins, which directly contact the mature miRNA, decreased expression of miRNAs. Quantitative analysis indicates compensation to maintain the overall pool of AGO after knockout of AGO variants. Evaluation of miRNA binding to AGO proteins revealed that association between AGO and miRNAs was similar for AGO1 - 4. Contrary to the assumptions underlying many peer-reviewed reports, not all annotated miRNAs have equal potential as biological regulators. Cellular abundance, DROSHA dependence, and physical association with AGO must be considered when forming hypotheses related to their function. Our data prioritize sixty miRNAs - under two percent of the overall annotated miRNA repertoire - as being most likely to function as robust gene regulators. Our approach will facilitate identifying biologically active miRNAs.

biochemistry↗

bioRxiv2022

Optical Biopsy using a neural network to predict functional state from photos of wounds

BackgroundThe clinical characterization of the functional status of active wounds remains a considerable challenge that at present, requires excision of a tissue biopsy. In this pilot study, we use a convolutional Siamese neural network architecture to predict the functional state of a wound using digital photographs of wounds in a canine model of volumetric muscle loss (VML). Materials and MethodsImages of volumetric muscle loss injuries and tissue biopsies were obtained in a canine model of VML. Gene expression profiles for each image were obtained using RNAseq. These profiles were then converted to functional profiles using a manual review of validated gene ontology databases. A Siamese neural network was trained to regress functional profile expression values as a function of the data contained in an extracted image segment showing the surface of a small tissue biopsy. Network performance was assessed in a test set of images using Mean Absolute Percentage Error (MAPE). ResultsThe network was able to predict the functional expression of a range of functions based with a MAPE ranging from [~]5% to [~]50%, with functions that are most closely associated with the early-state of wound healing to be those best-predicted. ConclusionsThese initial results suggest promise for further research regarding this novel use of ML regression on medical images. The regression of functional profiles, as opposed to specific genes, both addresses the challenge of genetic redundancy and gives a deeper insight into the mechanistic configuration of a region of tissue in wounds. As this preliminary study focuses on the first 14 days of wound healing, future work will focus on extending the training data to include longer time periods which would result in additional functions, such as tissue remodeling, having a larger presence in the training data.

bioinformatics↗

bioRxiv2022

Bordetella Spp. Utilize T3SS To Promote Secretion of IL1RA Leading to Long-Term Per-sistent Infections

A common feature of pathogens is their ability to suppress host immune responses. Understanding the molecular mechanisms and the common pathways that bacteria utilize to block host immune signaling cascade might provide novel avenues for vaccine and therapeutic development. Preventable infectious diseases remain one of the major causes of morbidity and mortality worldwide and the current rise in antibiotic resistance is increasing this burden. Bordetella spp. are respiratory pathogens that cause the long-term illness known as whooping cough. Bordetella infections cause over 150,000 deaths each year, despite a vaccine being available. In our studies, we used the mouse pathogen B. bronchiseptica to investigate the pneumonic stage of disease, which very well mimics the fatal disease caused by B. pertussis. In our previous work we discovered a B. bronchiseptica mutant, RB50{Delta}btrS, that clears rapidly from the lungs of mice and generates protective immunity that lasts for at least 15 months post-challenge. Combining the mouse immunological tools and both bacteria, the wildtype RB50 and mutant RB50{Delta}btrS, which persists for up to 56 days and clears in 14-21 days, respectively, we investigated the mechanisms by which the wildtype B. bronchiseptica blocks host immune response to cause long term lung infection. Previous research indicated eosinophils as critical for rapid clearance of the mutant bacteria from the lungs. In vitro assays with eosinophils demonstrated that the RB50{Delta}btrS mutant strain promotes the secretion of pro-inflammatory signals. In contrast, infection of eosinophils with RB50 promoted the secretion of anti-inflammatory signals such as IL1RA. Interestingly, IL1RA was also increased in the lungs of mice infected with the wildtype but not with the mutant RB50 strain. Infection with RB50{Delta}bscN, which lacks a functional type 3 secretion system (T3SS), was sufficient to prevent IL1RA induction suggesting that the bacterial effector responsible for IL1RA upregulation is a substrate of the T3SS. Supplementation with IL1RA after infection with RB50 or RB50{Delta}btrS resulted in increased lung bacterial burden for both bacterial strains. However, more rapid clearance of RB50 was observed after infection of mice in which IL1RA was knocked out. Furthermore, anti-IL1RA antibody treatment promoted rapid clearance of not only RB50 but also the human pathogens B. pertussis and B. parapertussis. This suggests that IL1RA may be a promising therapeutic target to treat severe cases of whooping cough. Overall, this work demonstrates that Bordetella spp. induces IL1RA expression to promote persistence using the T3SS. Since other bacteria have also been shown to target IL1RA, this may be a conserved bacterial mechanism to promote host-immune suppression.

microbiology↗

bioRxiv2022

SAMHD1 controls nucleoside-based cancer therapeutics, deoxyguanosine toxicity, and inflammation

SAMHD1 is a key regulator of dNTP metabolism, being activated by dGTP and converting dNTPs into their respective nucleosides. As a result, it plays a significant role in several distinct diseases. Not only is SAMHD1 a restriction factor for HIV-1 replication, which requires dNTPs for replication, but it is also required for genome stability, is mutated in multiple cancers, and loss of function mutations cause Acardi-Goutieres Syndrome, an early-onset inherited encephalopathy. In this paper we knock out the SAMHD1 gene in pluripotent stem cells, and show that it also affects nucleoside analogue sensitivity of dividing cells and deoxyguanosine toxicity in a cell cycle-independent manner. Comparing wild type and gene-edited macrophages, we also show that deoxyguanosine toxicity is associated with pro-inflammatory cell death, modifications in uric acid production and the formation of monosodium urate crystals within the macrophages. These novel features of the SAMHD1-/- phenotype provide unique insights into the aetiology of Acardi-Goutieres Syndrome, and have implications for certain chemotherapeutic agents.

pharmacology and toxicology↗