Biology subjects

Washington, M. K.

Publications and source records attributed to Washington, M. K..

At least 19 recordsLinked to original sources

bioRxiv2025

A targeted cell lysis mechanism facilitates toxin release in Clostridioides difficile

Clostridioides difficile infection depends on the production of two large toxins, TcdA and TcdB, encoded within a pathogenicity locus alongside the phage-like holin TcdE. The mechanism of toxin secretion remains actively debated, with current models proposing either TcdE-dependent non-lytic secretion or TcdE-independent lytic release. Here, we provide evidence for a unifying model where TcdE drives lysis in a phenotypically distinct subpopulation of cells. We show that TcdE, TcdA, and TcdB expression is restricted to a small fraction of cells exhibiting markers of active lysis and establish this subpopulation as the driver of severe pathogenic outcomes in a mouse model of CDI. Overexpression of TcdR, the sigma factor regulating the pathogenicity locus, triggers TcdE-dependent lysis, even in strains previously reported to employ TcdE-independent secretion mechanisms. Correlative light and electron microscopy combined with cryo-ET reveal a distinctive ultrastructure in lytic cells. Membrane vesicles accumulate between a disrupted inner membrane and intact peptidoglycan, alongside electron-dense material containing TcdA. These observations reveal a population-level strategy in which a minority of bacteria sacrifice themselves through TcdE-mediated lysis to release toxins as a 'bet-hedging strategy'.

microbiology↗

bioRxiv2025

Trsp is required by regulatory T cells to prevent lethal autoimmunity in mice

Selenoproteins are involved in immune cell metabolism, yet the roles of these proteins in T cell development and function remain largely unknown. The Trsp gene encodes the selenocysteine tRNA (tRNASec) required for translation of all selenoproteins. In this study, we found that Trsp was required for thymopoiesis, with the majority of tRNASec-deficient T cells not progressing beyond double negative 3 stage, with egressed thymocytes undergoing peripheral homeostatic expansion. Trsp-deficient CD4+ T cells exhibited impairments in TCR and IL-2 signaling and did not cause inflammation in experimental models. On the other hand, Trsp-deficient regulatory T (Treg) cells exhibited defects in suppressive function ex vivo and Treg-specific Trsp deletion using Trspfl/flFoxp3YFP-Cre (Trsp!{iota}Treg) mice caused fatal autoimmunity similar to FOXP3-deficient mice. Reducing oxidative stress via 2-HOBA administration prolonged survival in these Trsp!{iota}Treg mice. These findings indicate that tRNASec is required for T cell homeostasis and may be therapeutic targets in inflammation. One sentence summaryTrsp, a gene required for translation of all selenoproteins, is essential for all T cell development and function, especially regulatory T cells.

immunology↗

bioRxiv2025

An Anaerobic Pathogen Rewires Host Metabolism to Fuel Oxidative Growth in the Inflamed Gut

To colonize their host and cause disease, enteric pathogens must deploy their virulence factors to establish distinct nutrient niches. How obligate anaerobic pathogens construct nutrient niches in the densely populated large intestine remains poorly understood. Enterotoxigenic Bacteroides fragilis (ETBF) is considered an obligate anaerobic bacterium and has been implicated in inflammation-associated diseases, including colitis and colorectal cancer. Here we show that ETBF uses its virulence factor, Bacteroides fragilis toxin, to reprogram colonic epithelial cell metabolism to colonize the inflamed gut. Bacteroides fragilis toxin activates colonic epithelial signaling and hijacks the host bile acid recycling pathway, inducing a metabolic shift in the epithelium from oxidative phosphorylation to glycolysis. This shift increases local concentrations of lactate and oxygen, nutrients that support an oxidative metabolism in ETBF. These findings reveal an unexpected strategy by which a pathogenic organism, previously considered to be an obligate anaerobic bacterium, generates and exploits an oxidative niche in the inflamed gut.

microbiology↗

bioRxiv2025

Pathobiont-triggered induction of epithelial IDO1 drives regional susceptibility to Inflammatory Bowel Disease

The structure and function of the mammalian gut vary by region, yet why inflammatory diseases manifest in specific regions and not others remains unclear. We use a TNF-overexpressing Crohns disease (CD) model (Tnf{Delta}ARE/+), which typically presents in the terminal ileum (TI), to investigate how environmental factors interact with the hosts immune susceptibility to drive region-specific disease. We identified Chlamydia muridarum, an intracellular bacterium and murine counterpart to the human sexually transmitted C. trachomatis, as necessary and sufficient to trigger disease manifestation in the ascending colon (AC), another common site of human CD. Disease manifestation in the AC depends on indoleamine 2,3-dioxygenase (IDO1) activity induced by hypersensitive surface secretory cells in genetically susceptible hosts. Single-cell and microbial analyses of human specimens also implicates this pathobiont-epithelial IDO1 pathway in patients with a history of CD in the AC. Our findings demonstrate that genetic and microbial factors can independently drive region-specific disease and provide a unique model to study CD specific to the AC.

cell biology↗

bioRxiv2024

Inhibition of EGFR/ErbB does not protect against C. difficile toxin B

Clostridioides difficile is a common cause of diarrhea and mortality, especially in immunosuppressed and hospitalized patients. C. difficile is a toxin-mediated disease, but the host cell receptors for C. difficile toxin B (TcdB) have only recently been revealed. Emerging data suggest TcdB interacts with receptor tyrosine kinases during infection. In particular, TcdB can elicit Epidermal Growth Factor Receptor (EGFR) transactivation in human colonic epithelial cells. The mechanisms for this function are not well understood, and the involvement of other receptors in the EGFR family of Erythroblastic Leukemia Viral Oncogene Homolog (ErbB) receptors remains unclear. Furthermore, in an siRNA-knockdown screen for protective genes involved with TcdB toxin pathogenesis, we show ErbB2 and ErbB3 loss resulted in increased cell viability. We hypothesize TcdB induces the transactivation of EGFR and/or ErbB receptors as a component of its cell-killing mechanism. Here, we show in vivo intrarectal instillation of TcdB in mice leads to phosphorylation of ErbB2 and ErbB3. However, immunohistochemical staining for phosphorylated ErbB2 and ErbB3 indicated no discernible difference between control and TcdB-treated mice for epithelial phospho-ErbB2 and phospho-ErbB3. Human colon cancer cell lines (HT29, Caco-2) exposed to TcdB were not protected by pre-treatment with lapatinib, an EGFR/ErbB2 inhibitor. Similarly, lapatinib pre-treatment failed to protect normal human colonoids from TcdB-induced cell death. Neutralizing antibodies against mouse EGFR failed to protect mice from TcdB intrarectal instillation as measured by edema, inflammatory infiltration, and epithelial injury. Our findings suggest TcdB-induced colonocyte cell death does not require EGFR/ErbB receptor tyrosine kinase activation.

microbiology↗

bioRxiv2024

Vaccination generates functional progenitor tumor-specific CD8 T cells and long-term tumor control

BackgroundImmune checkpoint blockade (ICB) therapies are an important treatment for patients with advanced cancers; however only a subset of patients with certain types of cancer achieves durable remissions. Cancer vaccines are an attractive strategy to boost patient immune responses, but less is known about whether and how immunization can induce long-term tumor immune reprogramming and arrest cancer progression. We developed a clinically-relevant genetic cancer mouse model in which hepatocytes sporadically undergo oncogenic transformation. We compared how tumor-specific CD8 T cells (TST) differentiate in mice with early sporadic lesions as compared to late lesions and tested how immunotherapeutic strategies, including vaccination and ICB, reprogram TST and impact liver cancer progression. MethodsMice with a germline floxed allele of the SV40 large T antigen (TAG) undergo spontaneous recombination and activation of the TAG oncogene, leading to rare early pre-cancerous lesions that inevitably progress to established liver cancer. We assessed the immunophenotype and function of TAG-specific CD8 T cells in mice with early and late liver lesions. We vaccinated mice, either alone or in combination with ICB, to test whether these immunotherapeutic interventions could stop liver cancer progression. ResultsIn mice with early lesions, a subset of TST were PD1+ TCF1+ TOX- and could produce IFN{gamma}, while TST present in mice with late liver cancers were PD1+ TCF1lo/- TOX+ and unable to make effector cytokines. Strikingly, vaccination with attenuated TAG epitope-expressing Listeria monocytogenes (LMTAG) blocked liver cancer development and led to a population of TST that were TCF1+ TOX- TST and polyfunctional cytokine producers. In contrast, ICB administration did not slow cancer progression or improve LMTAG vaccine efficacy. ConclusionVaccination, but not ICB, generated a population of progenitor TST and halted cancer progression in a clinically relevant model of sporadic liver cancer. In patients with early cancers or at high-risk of cancer recurrence, immunization may be the most effective strategy. What is already known on this topicImmunotherapy, including immune checkpoint blockade and cancer vaccines, fails to induce long-term remissions in most patients with cancer. What this study addsHosts with early lesions but not hosts with advanced cancer retain a progenitor TCF1+ TST population. This population can be reprogrammed and therapeutically exploited by vaccination, but not ICB, to block tumor progression. How this study might affect research, practice, or policyFor people at high-risk of cancer progression, vaccination administered when a responsive progenitor TST population is present may be the optimal immunotherapy to induce long-lasting progression-free survival.

cancer biology↗

bioRxiv2023

A Specialized Epithelial Cell Type Regulating Mucosal Immunity and Driving Human Crohn's Disease

Crohns disease (CD) is a complex chronic inflammatory disorder that may affect any part of gastrointestinal tract with extra-intestinal manifestations and associated immune dysregulation. To characterize heterogeneity in CD, we profiled single-cell transcriptomics of 170 samples from 65 CD patients and 18 non-inflammatory bowel disease (IBD) controls in both the terminal ileum (TI) and ascending colon (AC). Analysis of 202,359 cells identified a novel epithelial cell type in both TI and AC, featuring high expression of LCN2, NOS2, and DUOX2, and thus is named LND. LND cells, confirmed by high-resolution in-situ RNA imaging, were rarely found in non-IBD controls, but expanded significantly in active CD. Compared to other epithelial cells, genes defining LND cells were enriched in antimicrobial response and immunoregulation. Moreover, multiplexed protein imaging demonstrated that LND cell abundance was associated with immune infiltration. Cross-talk between LND and immune cells was explored by ligand-receptor interactions and further evidenced by their spatial colocalization. LND cells showed significant enrichment of expression specificity of IBD/CD susceptibility genes, revealing its role in immunopathogenesis of CD. Investigating lineage relationships of epithelial cells detected two LND cell subpopulations with different origins and developmental potential, early and late LND. The ratio of the late to early LND cells was related to anti-TNF response. These findings emphasize the pathogenic role of the specialized LND cell type in both Crohns ileitis and Crohns colitis and identify novel biomarkers associated with disease activity and treatment response.

bioinformatics↗

bioRxiv2023

Paeniclostridium sordellii NanS works synergistically with TcsL to increase cytotoxicity and the severity of pathogenesis in the murine uterus

Paeniclostridium sordellii, a pathogen capable of causing lethal uterine infections post-partum or post-abortion, produces a variety of potential virulence factors. Lethal toxin (TcsL) has been found to be essential for lethal P. sordellii infections, but the physiological role of NanS, a sialidase, remains elusive. Here, we purify enzymatically active P. sordellii NanS and report the crystal structure. We show that NanS works in a synergistic manner with TcsL to increase cytotoxicity and cell rounding of tissue culture cells. Using a mouse model of hormone-dependent uterine intoxication, we show that NanS augments TcsL-induced lethality in diestrus mice. In estrus mice, the combination of NanS and TcsL significantly increases uterine histologic damage compared to challenge with TcsL alone. This suggests that NanS enhancement of TcsL-induced uterine epithelial injury may potentiate TcsL access to the tissue when mucus is present. Author SummaryP. sordellii produces several proteins predicted to contribute to lethal uterine infections following childbirth, stillbirth, or abortion. The role of lethal toxin (TcsL) in causing lethal outcomes, has been well documented, but little is known of how NanS, a sialidase, contributes to disease development. Previous reports have suggested a role for NanS in increasing the tissue culture cell toxicity from P. sordellii supernatants. In this study, we show in cell culture and using a uterine mouse model that TcsL and NanS work together to increase cell cytotoxicity and to worsen disease outcome. This finding suggests an accessory role for NanS to enhance P. sordellii pathogenesis when host environmental conditions reduce the influence of TcsL.

microbiology↗

bioRxiv2023

Eosinophils exert direct and indirect anti-tumorigenic effects in the development of esophageal squamous cell carcinoma

Background/AimsEosinophils are present in several solid tumors and have context-dependent function. Our aim is to define the contribution of eosinophils in esophageal squamous cell carcinoma (ESCC), since their role in ESCC is unknown. MethodsEosinophils were enumerated in tissues from two ESCC cohorts. Mice were treated with 4-nitroquinolone-1-oxide (4-NQO) for 8 weeks to induce pre-cancer or 16 weeks to induce carcinoma. Eosinophil number was modified by monoclonal antibody to IL-5 (IL5mAb), recombinant IL-5 (rIL-5), or genetically with eosinophil-deficient ({Delta}dblGATA) mice or mice deficient in eosinophil chemoattractant eotaxin-1 (Ccl11-/-). Esophageal tissue and eosinophil specific RNA-sequencing was performed to understand eosinophil function. 3-D co-culturing of eosinophils with pre-cancer or cancer cells was done to ascertain direct effects of eosinophils. ResultsActivated eosinophils are present in higher numbers in early stage versus late stage ESCC. Mice treated with 4-NQO exhibit more esophageal eosinophils in pre-cancer versus cancer. Correspondingly, epithelial cell Ccl11 expression is higher in mice with pre-cancer. Eosinophil depletion using three mouse models (Ccl11-/- mice, {Delta}dblGATA mice, IL5mAb treatment) all display exacerbated 4-NQO tumorigenesis. Conversely, treatment with rIL-5 increases esophageal eosinophilia and protects against pre-cancer and carcinoma. Tissue and eosinophil RNA-sequencing revealed eosinophils drive oxidative stress in pre-cancer. In vitro co-culturing of eosinophils with pre-cancer or cancer cells resulted in increased apoptosis in the presence of a degranulating agent, which is reversed with N-acetylcysteine, a reactive oxygen species (ROS) scavenger. {Delta}dblGATA mice exhibited increased CD4 T cell infiltration, IL-17, and enrichment of IL-17 pro-tumorigenic pathways. ConclusionEosinophils likely protect against ESCC through ROS release during degranulation and suppression of IL-17.

cancer biology↗

bioRxiv2023

Molecular cartography uncovers evolutionary and microenvironmental dynamics in sporadic colorectal tumors

Colorectal cancer exhibits dynamic cellular and genetic heterogeneity during progression from precursor lesions toward malignancy. Leveraging spatial molecular information to construct a phylogeographic map of tumor evolution can reveal individualized growth trajectories with diagnostic and therapeutic potential. Integrative analysis of spatial multi-omic data from 31 colorectal specimens revealed simultaneous microenvironmental and clonal alterations as a function of progression. Copy number variation served to re-stratify microsatellite stable and unstable tumors into chromosomally unstable (CIN+) and hypermutated (HM) classes. Phylogeographical maps classified tumors by their evolutionary dynamics, and clonal regions were placed along a global pseudotemporal progression trajectory. Cell-state discovery from a single-cell cohort revealed recurring epithelial gene signatures and infiltrating immune states in spatial transcriptomics. Charting these states along progression pseudotime, we observed a transition to immune exclusion in CIN+ tumors as characterized by a novel gene expression signature comprised of DDR1, TGFBI, PAK4, and DPEP1. We demonstrated how these genes and their protein products are key regulators of extracellular matrix components, are associated with lower cytotoxic immune infiltration, and show prognostic value in external cohorts. Through high-dimensional data integration, this atlas provides insights into co-evolution of tumors and their microenvironments, serving as a resource for stratification and targeted treatment of CRC.

systems biology↗

bioRxiv2022

SMAD4 suppresses colitis-associated carcinoma through inhibition of CCL20/CCR6-mediated inflammation

Background & AimsChronic inflammation in the colon is a predisposing factor for colon cancer. We previously reported that colon epithelial cell silencing of Smad4, the central downstream mediator of TGF{beta} family signaling, increased epithelial expression of inflammatory genes, including the chemokine CCL20, and increased susceptibility to colitis-associated cancer. Here, we examine the role of the chemokine/receptor pair CCL20/CCR6 in mediating colitis-associated colon carcinogenesis induced by SMAD4 loss. MethodsMice with conditional, epithelial-specific Smad4 loss with and without germline deletion of the Ccr6 gene were subjected to three rounds of dextran sodium sulfate and followed for up to 3 months. Tumors were quantified histologically, and immune cell populations were analyzed by flow cytometry and immunostaining. ResultsIn humans, SMAD4 expression inversely correlated with CCL20 expression. Smad4 loss in mouse colon epithelium led to enlarged gut-associated lymphoid tissues and recruitment of specific immune cell subsets to the mouse colon epithelium and underlying stroma, particularly Treg, Th17, and dendritic cells. Loss of CCR6 abrogated these immune responses and significantly reduced the incidence of colitis-associated tumors observed with loss of SMAD4 alone. ConclusionsRegulation of mucosal inflammation is a critical role of SMAD4 signaling within the colon epithelium and central to its tumor suppressor function in the colon. A key downstream node in this regulation is suppression of CCL20 signaling by the epithelium to CCR6 in immune cells. Loss of SMAD4 in the colon epithelium increases CCL20 expression and chemoattraction of CCR6+ immune cells, contributing to greater susceptibility to colon cancer.

cancer biology↗

bioRxiv2021

MTG16 (CBFA2T3) represses E protein-dependent transcription to regulate colonic secretory cell differentiation, epithelial regeneration, and tumorigenesis

Aberrant epithelial differentiation and regeneration contribute to colon pathologies including inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). MTG16 (CBFA2T3) is a transcriptional corepressor expressed in the colonic epithelium. MTG16 deficiency in mice exacerbates colitis and increases tumor burden in CAC, though the underlying mechanisms remain unclear. Here, we identified MTG16 as a central mediator of epithelial differentiation, promoting goblet and restraining enteroendocrine cell development in homeostasis and enabling regeneration following dextran sulfate sodium (DSS)-induced colitis. Transcriptomic analyses implicated increased E box-binding transcription factor (E protein) activity in MTG16-deficient colon crypts. Using a novel mouse model with a point mutation that disrupts MTG16:E protein complex formation (Mtg16P209T), we established that MTG16 exerts control over colonic epithelial differentiation and regeneration by repressing E protein-mediated transcription. Mimicking murine colitis, MTG16 expression was increased in biopsies from patients with active IBD compared to unaffected controls. Finally, uncoupling MTG16:E protein interactions only partially phenocopied the enhanced tumorigenicity of Mtg16-/- colon in the azoxymethane(AOM)/DSS-induced model of CAC, indicating that MTG16 protects from tumorigenesis through additional mechanisms. Collectively, our results demonstrate that MTG16, via its repression of E protein targets, is a key regulator of cell fate decisions during colon homeostasis, colitis, and cancer. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/467178v3_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@21948borg.highwire.dtl.DTLVardef@9f60eeorg.highwire.dtl.DTLVardef@194b9fdorg.highwire.dtl.DTLVardef@13eb1a7_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2021

Glucosyltransferase-dependent and independent effects of Clostridioides difficile toxins during infection

Clostridioides difficile infection (CDI) is the leading cause of nosocomial diarrhea and pseudomembranous colitis in the USA. In addition to these symptoms, patients with CDI can develop severe inflammation and tissue damage, resulting in life-threatening toxic megacolon. CDI is mediated by two large homologous protein toxins, TcdA and TcdB, that bind and hijack receptors to enter host cells where they use glucosyltransferase (GT) enzymes to inactivate Rho family GTPases. GT-dependent intoxication elicits cytopathic changes, cytokine production, and apoptosis. At higher concentrations TcdB induces GT-independent necrosis in cells and tissue by stimulating production of reactive oxygen species via recruitment of the NADPH oxidase complex. Although GT-independent necrosis has been observed in vitro, the relevance of this mechanism during CDI has remained an outstanding question in the field. In this study we generated novel C. difficile toxin mutants in the hypervirulent BI/NAP1/PCR-ribotype 027 R20291 strain to test the hypothesis that GT-independent epithelial damage occurs during CDI. Using the mouse model of CDI, we observed that epithelial damage occurs through a GT-independent process that is does not involve immune cell influx. The GT-activity of either toxin was sufficient to cause severe edema and inflammation, yet GT activity of both toxins was necessary to produce severe watery diarrhea. These results indicate that both TcdA and TcdB contribute to infection when present. Further, while inactivating GT activity of C. difficile toxins may suppress diarrhea and deleterious GT-dependent immune responses, the potential of severe GT-independent epithelial damage merits consideration when developing toxin-based therapeutics against CDI. SIGNIFICANCEClostridioides difficile is the leading cause of antibiotic-associated diarrhea in hospitals worldwide. This bacterium produces two virulence factors, TcdA and TcdB, which are large protein toxins that enter host colon cells to cause inflammation, fluid secretion, and cell death. The enzymatic domain of TcdB is a target for novel C. difficile infection (CDI) therapeutics since it is considered the major factor in causing severe CDI. However, necrotic cell death due to non-enzymatic TcdB-host interactions have been reported in cell culture and intoxicated tissue. Here, we generated C. difficile strains with enzyme-inactive toxins to evaluate the role of each toxin in an animal model of CDI. We observe an additive role for TcdA and TcdB in disease and both glucosyltransferase-dependent and independent phenotypes. These findings are expected to inform the development of toxin-based CDI therapeutics.

pathology↗

bioRxiv2021

Anal skin-like epithelium mediates colonic wound healing

Intestinal epithelial wound healing, which is essential for health, is compromised and represents a therapeutic target in inflammatory bowel disease (IBD). While studies have elucidated important subpopulations of intestinal epithelial cells in repair, these have yet to translate to therapies. Here, in mouse models of acute colitis, we demonstrate a distinct and essential source of wound-healing cells that re-epithelialize the distal colon. Using 3-d imaging, lineage tracing, and single-cell transcriptomics, we show that neighboring skin-like (squamous) cells of the anus rapidly migrate into the injured colon and establish a permanent epithelium of crypt-like morphology. These squamous cells derive from a small unique transition zone, at the boundary of colonic and anal epithelium, that resists colitis. The cells of this zone have a pre-loaded program of colonic differentiation and further upregulate key aspects of colonic epithelium during repair. Thus, heterologous cell-types at tissue junctions represent unique reserve cells capable of repair and plasticity.

developmental biology↗

bioRxiv2021

Human colorectal pre-cancer atlas identifies distinct molecular programs underlying two major subclasses of pre-malignant tumors

Most colorectal cancers (CRCs) develop from either adenomas (ADs) or sessile serrated lesions (SSLs). The origins and molecular landscapes of these histologically distinct pre-cancerous polyps remain incompletely understood. Here, we present an atlas at single-cell resolution of sporadic conventional tubular/tubulovillous ADs, SSLs, hyperplastic polyps (HPs), microsatellite stable (MSS) and unstable (MSI-H) CRC, and normal colonic mucosa. Using single-cell transcriptomics and multiplex imaging, we studied 69 datasets from 33 participants. We also examined separate sets of 66 and 274 polyps for RNA and targeted gene sequencing, respectively. We performed multiplex imaging on a tissue microarray of 14 ADs and 15 CRCs, and we integrated pre-cancer polyp data with published single-cell and The Cancer Genome Atlas (TCGA) bulk CRC data to establish potential polyp-cancer relationships. Striking differences were observed between ADs and SSLs that extended to MSS and MSI-H CRCs, respectively, reflecting their distinct origins and trajectories. ADs arose from WNT pathway dysregulation in stem cells, which aberrantly expanded and expressed a Hippo and ASCL2 regenerative program. In marked contrast, SSLs were depleted of stem cell-like populations and instead exhibited a program of gastric metaplasia in the setting of elevated cytotoxic inflammation. Using subtype-specific gene regulatory networks and shared genetic variant analysis, we implicated serrated polyps, including some HPs conventionally considered benign, as arising from a metaplastic program in committed absorptive cells. ADs and SSLs displayed distinct patterns of immune cell infiltration that may influence their natural history. Our multi-omic atlas provides novel insights into the malignant potential of colorectal polyps and serves as a framework for precision surveillance and prevention of sporadic CRC.

cancer biology↗

bioRxiv2020

Murine intrarectal instillation of purified recombinant C. difficile toxins enables mechanistic studies of pathogenesis

Clostridioides difficile is linked to nearly 225,000 antibiotic-associated diarrheal infections and almost 13,000 deaths per year in the United States. Pathogenic strains of C. difficile produce toxin A (TcdA) and toxin B (TcdB), which can directly kill cells and induce an inflammatory response in the colonic mucosa. Hirota, et al. first introduced the intrarectal instillation model of intoxication using TcdA and TcdB purified from VPI 10463 and 630 C. difficile strains. Here, we expand this technique by instilling purified, recombinant TcdA and TcdB, which allows for the interrogation of how specifically mutated toxins affect tissue. Mouse colons were processed and stained with hematoxylin and eosin (H&E) for blinded evaluation and scoring by a board-certified gastrointestinal pathologist. The amount of TcdA or TcdB needed to produce damage was lower than previously reported in vivo and ex vivo. Furthermore, TcdB mutants lacking either endosomal pore-formation or glucosyltransferase activity resemble sham negative controls. Immunofluorescent staining revealed how TcdB initially damages colonic tissue by altering the epithelial architecture closest to the lumen. Tissue sections were also immunostained for markers of acute inflammatory infiltration. These staining patterns were compared with slides from a human C. difficile infection (CDI). The intrarectal instillation mouse model with purified recombinant TcdA and/or TcdB provides the flexibility needed to better understand structure/function relationships across different stages of CDI pathogenesis.

microbiology↗

bioRxiv2020

Sprouty2 limits intestinal tuft and goblet cell numbers through GSK3β-mediated restriction of epithelial IL-33.

Dynamic regulation of intestinal cell differentiation is crucial for both homeostasis and the response to injury or inflammation. Sprouty2, an intracellular signaling regulator, controls pathways including PI3K and MAPKs that are implicated in differentiation and are dysregulated in inflammatory bowel disease. Here, we asked whether Sprouty2 controls secretory cell differentiation and the response to colitis. We report that colonic epithelial Sprouty2 deletion led to expanded goblet and tuft cell populations. Sprouty2 loss induced PI3K/Akt signaling, leading to GSK3{beta} inhibition and epithelial interleukin (IL)-33 expression. In vivo, this resulted in increased stromal IL-13+ cells. IL-13 in turn induced tuft and goblet cell expansion in vitro and in vivo. Sprouty2 was downregulated by inflammation; this appeared to be a protective response, as VillinCre;Sprouty2F/F mice were resistant to DSS colitis. In contrast, Sprouty2 was elevated in colons of inflammatory bowel disease patients, suggesting that this protective epithelial-stromal signaling mechanism is lost in disease.

physiology↗

bioRxiv2019

Commensal-derived succinate enhances tuft cell specification and suppresses ileal inflammation

Longitudinal analysis of Crohn's disease (CD) incidence has identified an inverse correlation with helminth infestation and recent studies have revealed that intestinal tuft cell hyperplasia is critical for helminth response. Tuft cell frequency was decreased in the inflamed ilea of CD patients and a mouse model of TNF-induced Crohn's-like ileitis (TNF{Delta}ARE). Single-cell RNA sequencing paired with unbiased differential trajectory analysis of the tuft cell lineage in a genetic model of tuft cell hyperplasia (AtohKO) demonstrated that the tuft cell lineage had increased tricarboxylic acid (TCA) cycle gene signatures. Commensal microbiome-derived succinate was detected in the ileal lumen of these animals while microbiome depletion suppressed tuft cell hyperplasia. Therapeutic succinate treatment in TNF{Delta}ARE animals reduced pathology in correlation with induced tuft cell specification. We provide evidence implicating the modulatory role of intestinal tuft cells in chronic intestinal inflammation, which could facilitate leveraging this rare and elusive cell type for CD treatment.

cell biology↗