Tuft Cells Research Articles

POU2F3-expressing intraepithelial small-cell carcinoma with mixed small-cell carcinoma and conventional-type urothelial carcinoma of the urinary bladder.

Based on lineage-specific transcription factors, small-cell neuroendocrine carcinoma (SmCC) of the urinary bladder has recently been subtyped into three molecular subtypes: ASCL1, NEUROD1 and POU2F3. The latter is a master transcriptional regulator of tuft cells (TCs) which are rare solitary cells found in various mucosal epithelia such as the gastrointestinal tract, but which have not been reported in the bladder. The POU2F3 subtype shows low or absent neuroendocrine marker expression. A case of mixed SmCC and conventional-type urothelial carcinoma (CUC) of the urinary bladder with POU2F3-expressing intraepithelial small-cell carcinoma in keeping with a tuft cell phenotype, arising in association with intestinal metaplasia (IM) is described. The presence of POU2F3-expressing cells in normal urothelium, cystitis cystica glandularis and IM of the urinary bladder is demonstrated in separate cases of cystitis cystica glandularis with IM. Also, POU2F3 expression is identified in a subset of bladder SmCC.

The role of goblet cells in Crohn' s disease.

The prevalence of Crohn's disease (CD), a subtype of inflammatory bowel disease (IBD), is increasing worldwide. The pathogenesis of CD is hypothesized to be related to environmental, genetic, immunological, and bacterial factors. Current studies have indicated that intestinal epithelial cells, including columnar, Paneth, M, tuft, and goblet cells dysfunctions, are strongly associated with these pathogenic factors. In particular, goblet cells dysfunctions have been shown to be related to CD pathogenesis by direct or indirect ways, according to the emerging studies. The mucus barrier was established with the help of mucins secreted by goblet cells. Not only do the mucins mediate the mucus barrier permeability and bacterium selection, but also, they are closely linked with the endothelial reticulum stress during the synthesis process. Goblet cells also play a vital role in immune response. It was indicated that goblet cells take part in the antigen presentation and cytokines secretion process. Disrupted goblet cells related immune process were widely discovered in CD patients. Meanwhile, dysbiosis of commensal and pathogenic microbiota can induce myriad immune responses through mucus and goblet cell-associated antigen passage. Microbiome dysbiosis lead to inflammatory reaction against pathogenic bacteria and abnormal tolerogenic response. All these three pathways, including the loss of mucus barrier function, abnormal immune reaction, and microbiome dysbiosis, may have independent or cooperative effect on the CD pathogenesis. However, many of the specific mechanisms underlying these pathways remain unclear. Based on the current understandings of goblet cell's role in CD pathogenesis, substances including butyrate, PPARγagonist, Farnesoid X receptor agonist, nuclear factor-Kappa B, nitrate, cytokines mediators, dietary and nutrient therapies were all found to have potential therapeutic effects on CD by regulating the goblet cells mediated pathways. Several monoclonal antibodies already in use for the treatment of CD in the clinical settings were also found to have some goblet cells related therapeutic targets. In this review, we introduce the disease-related functions of goblet cells, their relationship with CD, their possible mechanisms, and current CD treatments targeting goblet cells.

Functionally diverse thymic medullary epithelial cells interplay to direct central tolerance

Medullary thymic epithelial cells (mTECs) are essential for the establishment of self-tolerance in Tcells. Promiscuous gene expression by a subpopulation of mTECs regulated by the nuclear protein Aire contributes to the display of self-genomic products to newly generated Tcells. Recent reports have highlighted additional self-antigen-displaying mTEC subpopulations, namely Fezf2-expressing mTECs and a mosaic of self-mimetic mTECs including thymic tuft cells. In addition, a functionally different subset of mTECs produces chemokine CCL21, which attracts developing thymocytes to the medullary region. Here, we report that CCL21+ mTECs and Aire+ mTECs non-redundantly cooperate to direct self-tolerance to prevent autoimmune pathology by optimizing the deletion of self-reactive Tcells and the generation of regulatory Tcells. We also detect cooperation for self-tolerance between Aire and Fezf2, the latter of which unexpectedly regulates thymic tuft cells. Our results indicate an indispensable interplay among functionally diverse mTECs for the establishment of central self-tolerance.

Salicin alleviates periodontitis via Tas2r143/gustducin signaling in fibroblasts.

Cells expressing taste signaling elements in non-gustatory tissues have been described as solitary chemosensory cells (SCCs) or tuft cells. These "taste-like" cells play a critical role in the maintenance of tissue homeostasis. Although the expression of SCC markers and taste signaling constituents has been identified in mouse gingivae, their role in periodontal homeostasis is still unclear. Public RNA sequencing datasets were re-analyzed and further validated with RT-PCR/qRT-PCR and immunofluorescent staining to explore the expression of TAS2Rs and downstream signaling constituents in mouse gingival fibroblasts (MGFs). The specific action of salicin on MGFs via Tas2r143 was validated with RNA silence, heterologous expression of taste receptor/Gα-gustducin and calcium imaging. The anti-inflammatory effects of salicin against LPS-induced MGFs were investigated in cell cultures, and were further validated with a ligature-induced periodontitis mouse model using Ga-gustducin-null (Gnat3-/-) mice. The expression of Tas2r143, Gnat3, Plcb2, and TrpM5 was detected in MGFs. Moreover, salicin could activate Tas2r143, elicited taste signaling and thus inhibited LPS-induced chemokines expression (CXCL1, CXCL2, and CXCL5) in MGFs. Consistently, salicin-treatment inhibited periodontal bone loss, inflammatory/chemotactic factors expression, and neutrophil infiltration in periodontitis mice, while these effects were abolished in Gnat3-/- mice. Gingival fibroblasts play a critical role in the maintenance of periodontal homeostasis via "SCC-like" activity. Salicin can activate Tas2r143-mediated bitter taste signaling and thus alleviate periodontitis in mouse, indicating a promising approach to the resolution of periodontal inflammation via stimulating the "SCC-like" function of gingival fibroblasts.

Abstract 1403: The role of Dclk1-expression cells in normal pancreas and in pancreatic tumor progression

Abstract Background: Tuft cells, marked by Doublecortin-like kinase-1 (Dclk1), are rare in the healthy pancreas but increase markedly during pancreatic tumorigenesis. While Group 2 innate lymphoid cells (ILC2s) are known to modulate inflammation and immunity, their specific roles in cancer-related immunity and immunotherapy interactions with pancreatic tuft cells remain unknown. Methods: To investigate tuft cells during early pancreatic neoplasia, we used a Dclk1 reporter mouse model and single-cell RNA-seq to study Dclk1-expressing cells in normal pancreas and neoplasia using Mist1/Kras mouse. We treated mice with IL-13 peptides and anti-IL-13 antibodies to explore the IL-13-ILC2 axis in tuft cell regulation. Results: Within the normal pancreas, Dclk1 expression marked several specialized epithelial cell types, including tuft-like cells, neuroendocrine cells, and a small number of acinar progenitor cells. A notable increase in Dclk1-expressing cells was observed at the onset of early PanIN lesions, with a subsequent decline in advanced PanIN stages and PDAC. Using flow cytometric analysis, we observed an increase in ILC2 cells in the Mist1/Kras pancreas in response to IL33 produced by pancreatic cancer-associated fibroblasts (CAFs). Blocking ILC2 activation with anti-IL33 antibodies reduced Dclk1 cell hyperplasia during PanIN progression. Given the known association between tuft cells, ILC2 cells, and the IL13/IL4 signaling pathways in the intestine, we discovered that Dclk1-expressing cells highly expressed the IL4 receptor (IL4ra). IL-13 levels increased during PanIN progression, and we found that ILC2s comprised the primary source of IL-13 within pancreatic tumors. In vitro, studies showed that the presence of IL-13 maintained the expansion of Dclk1-expressing tuft-like cells in pancreatic organoids derived from Dclk1-DTR-ZsGreen mice. Correspondingly, the in vivo administration of anti-IL-13 resulted in reduced Dclk1 expression. Conclusion: Previous studies have shown that pancreatic tuft cells inhibit pancreatic cancer progression. Our study reveals a novel regulatory mechanism wherein IL-13 secreted by ILC2s modulates Dclk1 tuft cell expression during pancreatic tumorigenesis. The IL13-ILC2 axis appears to be a potential therapeutic target to regulate Dclk1 cell activity, which could influence the course of pancreatic tumorigenesis. Future investigations will further explore the interaction between the IL13/ILC2 axis and Dclk1 in pancreatic cancer development. Citation Format: Giovanni Valenti, Pasquale Laise, Feijing Wu, Hiroki Kobayashi, Quin T. Waterbury, Ryota Takahashi, Tuo Ruan, Zhengyu Jiang, Yosuke Ochiai, Leah B. Zamechek, Timothy C. Wang. The role of Dclk1-expression cells in normal pancreas and in pancreatic tumor progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1403.

Intestinal tuft cell immune privilege enables norovirus persistence.

The persistent murine norovirus strain MNVCR6 is a model for human norovirus and enteric viral persistence. MNVCR6 causes chronic infection by directly infecting intestinal tuft cells, rare chemosensory epithelial cells. Although MNVCR6 induces functional MNV-specific CD8+ T cells, these lymphocytes fail to clear infection. To examine how tuft cells promote immune escape, we interrogated tuft cell interactions with CD8+ T cells by adoptively transferring JEDI (just EGFP death inducing) CD8+ T cells into Gfi1b-GFP tuft cell reporter mice. Unexpectedly, some intestinal tuft cells partially resisted JEDI CD8+ T cell-mediated killing-unlike Lgr5+ intestinal stem cells and extraintestinal tuft cells-despite seemingly normal antigen presentation. When targeting intestinal tuft cells, JEDI CD8+ T cells predominantly adopted a T resident memory phenotype with decreased effector and cytotoxic capacity, enabling tuft cell survival. JEDI CD8+ T cells neither cleared nor prevented MNVCR6 infection in the colon, the site of viral persistence, despite targeting a virus-independent antigen. Ultimately, we show that intestinal tuft cells are relatively resistant to CD8+ T cells independent of norovirus infection, representing an immune-privileged niche that can be leveraged by enteric microbes.

Abstract 1259: HMGA1: An epigenetic gatekeeper of Wnt signals during colon tumorigenesis and regeneration

Abstract Cancer cells undergo epigenetic reprogramming to co-opt stem cell networks and drive tumor progression, although how this occurs remains unclear. The High Mobility Group A1 (HMGA1) gene encodes an architectural transcription factor that binds to DNA at AT-rich sequences where it recruits chromatin complexes to modulate gene expression. HMGA1 is highly expressed during embryogenesis and in adult stem cells, but silenced in differentiated cells. HMGA1 becomes re-expressed in aggressive cancers where high levels portend adverse outcomes. In colorectal cancer (CRC), HMGA1 is among the genes most highly overexpressed compared to normal colon epithelium. We previously discovered that HMGA1 is required for oncogenic phenotypes in CRC cell lines by inducing genes involved in an epithelial-mesenchymal transition. Hmga1 transgenic mice also develop aberrant proliferation and polyposis of small intestinal epithelium where Hmga1 amplifies Wnt signals to enhance self-renewal. To determine how HMGA1 functions in colon epithelial homeostasis and tumorigenesis, we examined mouse models with overexpression or deficiency of Hmga1. Here, we uncover a previously unknown role for HMGA1 as an epigenetic gatekeeper of Wnt signals in colon epithelial cells, both during tumorigenesis driven by mutant APC or stress-induced tissue repair. Strikingly, loss of just a single Hmga1 allele within the colon epithelium disrupts tumorigenesis while prolonging survival in two models of colon tumorigenesis driven by APC mutation, including CDX2P-CreERTCApcfl/fl and APCMin mice inoculated with pro-carcinogenic, enterotoxigenic Bacteroides fragilis. Single cell RNA sequencing in Apc mutant crypt epithelial cells reveals that intact Hmga1 is required for expansion in the Lgr5+ stem cell pool, deep secretory cells, and tuft cells during tumorigenesis. Hmga1 deficiency impacts the stem cell pool the greatest, decreasing Lgr5+ stem cells with skewing to more proliferative, transit amplifying-like cells. Single cell transcriptomic analyses together with assays of single cell chromatin accessibility demonstrate that Hmga1 maintains accessible chromatin to activate gene loci involved in Wnt signals, including Ascl2, a stem cell master regulator, Wnt agonist receptors, and Wnt downstream effectors. Surprisingly, either depletion or overexpression of Hmga1 has no impact on colon epithelial regeneration under homeostatic conditions, although Hmga1 overexpression enhances tissue repair and survival following injury induced by inflammation or irradiation. Together, our results establish HMGA1 as an epigenetic gatekeeper of Wnt signals in colon stem cells during APC-driven tumorigenesis or injury, but not steady state homeostasis, highlighting its role as a promising therapeutic target for both cancer and regenerative medicine. Citation Format: Linda M. S. Resar, Li Z. Luo, Lingling Xian, Iliana Herrera, Shaoguang Wu, Jung-Hyun Kim, Ying Feng, Julian Calderon-Espinosa, Eric R. Fearon, Cynthia Sears. HMGA1: An epigenetic gatekeeper of Wnt signals during colon tumorigenesis and regeneration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1259.

Abstract 6602: Targeting the SWI/SNF complex in POU2F-POU2AF transcription factor-driven malignancies

Abstract Background: Small cell lung cancer (SCLC) is a rapidly progressing subtype of lung cancer with a high growth rate and early metastasis propensity, often resulting in a more advanced disease stage at diagnosis. A recent transcriptome analysis of human SCLC tumors revealed that SCLC could be characterized by the expression pattern of certain transcription factors (TFs), including ASCL1 (achaete-scute family bHLH transcription factor 1) and POU2F3 (POU domain class 2 transcription factor 3), exemplifying SCLC as a TF-driven malignancy. ASCL1-driven SCLC (SCLC-A) manifests a neuroendocrine phenotype, while POU2F3-driven SCLC (SCLC-P) is characterized as a tuft-cell-like variant. Recent studies revealed that POU domain class 2 transcription factors uniquely rely on coactivators to achieve their lineage-defining functions in the tuft cell and B cell lineages. In tuft-cell-like SCLC cells, the coactivators of POU2F3 (POU2AF2 and POU2AF3) endow POU2F3 with a critical transactivation domain by forming a master regulator complex, which supports enhancer-mediated cancer-promoting gene activation in SCLC-P cells. This indicates a potential therapeutic vulnerability of tuft-cell-like SCLC whereby strategies aimed at blocking POU2F3-POU2AF2/3 function may lead to clinical benefit. Methods: We conducted a domain-targeted CRISPR screen to identify druggable targets for SCLC-P, followed by pharmacological validation in preclinical SCLC models. Multi-omics techniques, including ATAC-seq, ChIP-seq, RNA-seq, and RIME, were employed to elucidate the SWI/SNF complex's regulatory influence on the POU2F-POU2AF axis. Results: Here we identified that the POU2F3 molecular subtype of SCLC (SCLC-P) exhibits an exquisite dependence on the activity of the SWI/SNF epigenetic complex. SCLC-P cell lines were sensitive to low nanomolar levels of a SWI/SNF ATPase degrader when compared to other molecular subtypes of SCLC. Co-factors of POU2F were found to interact with components of the SWI/SNF complex. The POU2F3 transcription factor complex is evicted from chromatin upon SWI/SNF ATPase degradation. A novel, orally bioavailable SWI/SNF ATPase PROTAC degrader demonstrated preferential efficacy in SCLC-P relative to the SCLC-A subtype. The SWI/SNF ATPase PROTAC degrader did not alter normal tuft cell numbers in lung or colon, nor did it exhibit toxicity in mice. B cell malignancies which displayed a dependency on the POU2F co-factor, POU2AF1, were also remarkably sensitive to SWI/SNF ATPase degradation. In a POU2AF1-dependent, disseminated murine model of multiple myeloma, AU-24118 had an enhanced survival benefit as compared to pomalidomide, an approved treatment for multiple myeloma. Conclusions: Taken together, our studies suggest that POU2F-POU2AF driven malignancies have an intrinsic dependence on the SWI/SNF complex representing a striking therapeutic vulnerability. Citation Format: Lanbo Xiao, Tongchen He, Olaf Klingbeil, Young Eleanor, Xiaoli Wu, Yuanyuan Qiao, Abhijit Parolia, Sanjana Eyunni, Rahul Mannan, Somnath Mahapatra, NamHoon Kim, Heng Zheng, Fengyun Su, Xuhong Cao, Susanta Samajdar, Murali Ramachandra, Christopher R. Vakoc, Arul M. Chinnaiyan. Targeting the SWI/SNF complex in POU2F-POU2AF transcription factor-driven malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6602.

Abstract 6885: Investigating a novel role of DCLK1 isoforms in colitis and colitis associated colon cancer

Abstract Chronic intestinal inflammation in patients diagnosed with inflammatory bowel disease (IBD) significantly increases their risk of colorectal cancer (CRC). Despite the rising global frequency of IBD, the precise mechanisms that regulate the transition from IBD to colon cancer are poorly understood. Doublecortin-like kinase 1 (DCLK1) is a protein with two major isoforms, DCLK1-L and DCLK1-S. Previous studies have shown that hypermethylation of the DCLK-1α promoter encoding DCLK1-L, particularly in colorectal cancer, allows switching to the DCLK1-S isoform that confers an invasive tumor phenotype. The DCLK1-L is a tuft cell marker that protects against colitis by sensing and eliminating gut pathogenic infection through various mechanisms. On the contrary, the role of DCLK1-S in colitis and colitis-associated cancer has not been thoroughly investigated. Studies from our lab have identified a marked elevation of DCLK1-S in tissue samples of IBD patients. We also recently discovered that DCLK1-S is predominantly expressed in Ly6G+; MHCII- neutrophils, which coincide with elevated levels of inflammation and tissue damage in the colon. To further understand the role of DCLK1 isoforms in driving the progression of colitis to colon cancer, we bred Dclk1fl/fl mice with MRP8-Cre-ires/GFP mice to generate Dclk1fl/fl;MRP8-Cre+/- that eliminates DCLK1-L upon tamoxifen injection resulting in sustained expression of DCLK1-S in the granulocytes especially neutrophils. When infected with Citrobacter rodentium (CR), MRP8;Dclk1−/− mice compared to MRP8;Dclk1+/− or WT mice developed more severe colitis. We have also discovered a novel interaction between DCLK1-S and MMP13 in an unbiased docking study that correlated with significant co-localization of DCLK1-S with MMP13 in the colons of CR-infected mice. Employing a knock-in mice over-expressing the DCLK1-S +19 under the CAG promoter, the DCLK1-MMP13 co-localization correlated with severe ulceration and colitis with loss of crypts and immune cell infiltration including Ly6G+ neutrophils. Studies are underway to see if the severity of colitis in MRP8;Dclk1−/− mice translates into enhanced tumorigenesis and to see if potential interaction between DCLK1-S and MMP13 could provide a plausible mechanism of colitis progression to colon cancer through ECM remodeling and tissue damage. Citation Format: Kafayat Aderonke Yusuf, Badal C. Roy, Shrikant Anant, Shahid Umar. Investigating a novel role of DCLK1 isoforms in colitis and colitis associated colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6885.

Mice with a Pax2 missense variant display impaired glomerular repair.

PAX2 regulates kidney development and its expression persists in parietal epithelial cells (PECs), potentially serving as a podocyte reserve. We hypothesize that mice with a Pax2 pathogenic missense variant (Pax2A220G/+) have impaired PEC-mediated podocyte regeneration. Embryonic wild type mouse kidneys showed overlapping expression of PAX2/WT-1 until PEC and podocyte differentiation, reflecting a close lineage relationship. Embryonic and adult Pax2A220G/+ mice have reduced nephron number but demonstrated no glomerular disease under baseline conditions. Pax2A220G/+ compared to wild type mice were more susceptible to glomerular disease after Adriamycin-induced podocyte injury, as demonstrated by worsened glomerular scarring, increased podocyte foot process effacement and podocyte loss. There was a decrease in PAX2-expressing PECs in wild type mice after Adriamycin injury accompanied by the occurrence of PAX2/WT-1 co-expressing glomerular tuft cells. In contrast, Pax2A220G/+ mice showed no changes in the numbers of PAX2-expressing PECs after Adriamycin injury, associated with fewer PAX2/WT-1 co-expressing glomerular tuft cells compared to injured wild type mice. A subset of PAX2 expressing glomerular tuft cells after Adriamycin injury was increased in Pax2A220G/+ mice, suggesting a pathologic process given the worse outcomes observed in this group. Lastly, Pax2A220G/+ mice have increased numbers of glomerular tuft cells expressing Ki67 and CC3 compared to wild type after Adriamycin injury, consistent with maladaptive responses to podocyte loss. Collectively, our results suggest that decreased glomerular numbers in Pax2A220G/+ mice are likely compounded with the inability of their mutated PECs to regenerate podocyte loss, and together these two mechanisms drive the worsened FSGS phenotype in these mice.

Developmental conversion of thymocyte-attracting cells into self-antigen-displaying cells in embryonic thymus medulla epithelium

Thymus medulla epithelium establishes immune self-tolerance and comprises diverse cellular subsets. Functionally relevant medullary thymic epithelial cells (mTECs) include a self-antigen-displaying subset that exhibits genome-wide promiscuous gene expression promoted by the nuclear protein Aire and that resembles a mosaic of extrathymic cells including mucosal tuft cells. An additional mTEC subset produces the chemokine CCL21, thereby attracting positively selected thymocytes from the cortex to the medulla. Both self-antigen-displaying and thymocyte-attracting mTEC subsets are essential for self-tolerance. Here, we identify a developmental pathway by which mTECs gain their diversity in functionally distinct subsets. We show that CCL21-expressing mTECs arise early during thymus ontogeny in mice. Fate-mapping analysis reveals that self-antigen-displaying mTECs, including Aire-expressing mTECs and thymic tuft cells, are derived from CCL21-expressing cells. The differentiation capability of CCL21-expressing embryonic mTECs is verified in reaggregate thymus experiments. These results indicate that CCL21-expressing embryonic mTECs carry a developmental potential to give rise to self-antigen-displaying mTECs, revealing that the sequential conversion of thymocyte-attracting subset into self-antigen-displaying subset serves to assemble functional diversity in the thymus medulla epithelium.

Developmental conversion of thymocyte-attracting cells into self-antigen-displaying cells in embryonic thymus medulla epithelium.

Thymus medulla epithelium establishes immune self-tolerance and comprises diverse cellular subsets. Functionally relevant medullary thymic epithelial cells (mTECs) include a self-antigen-displaying subset that exhibits genome-wide promiscuous gene expression promoted by the nuclear protein Aire and that resembles a mosaic of extrathymic cells including mucosal tuft cells. An additional mTEC subset produces the chemokine CCL21, thereby attracting positively selected thymocytes from the cortex to the medulla. Both self-antigen-displaying and thymocyte-attracting mTEC subsets are essential for self-tolerance. Here, we identify a developmental pathway by which mTECs gain their diversity in functionally distinct subsets. We show that CCL21-expressing mTECs arise early during thymus ontogeny in mice. Fate-mapping analysis reveals that self-antigen-displaying mTECs, including Aire-expressing mTECs and thymic tuft cells, are derived from CCL21-expressing cells. The differentiation capability of CCL21-expressing embryonic mTECs is verified in reaggregate thymus experiments. These results indicate that CCL21-expressing embryonic mTECs carry a developmental potential to give rise to self-antigen-displaying mTECs, revealing that the sequential conversion of thymocyte-attracting subset into self-antigen-displaying subset serves to assemble functional diversity in the thymus medulla epithelium.

A SWI/SNF-dependent transcriptional regulation mediated by POU2AF2/C11orf53 at enhancer

Recent studies have identified a previously uncharacterized protein C11orf53 (now named POU2AF2/OCA-T1), which functions as a robust co-activator of POU2F3, the master transcription factor which is critical for both normal and neoplastic tuft cell identity and viability. Here, we demonstrate that POU2AF2 dictates opposing transcriptional regulation at distal enhance elements. Loss of POU2AF2 leads to an inhibition of active enhancer nearby genes, such as tuft cell identity genes, and a derepression of Polycomb-dependent poised enhancer nearby genes, which are critical for cell viability and differentiation. Mechanistically, depletion of POU2AF2 results in a global redistribution of the chromatin occupancy of the SWI/SNF complex, leading to a significant 3D genome structure change and a subsequent transcriptional reprogramming. Our genome-wide CRISPR screen further demonstrates that POU2AF2 depletion or SWI/SNF inhibition leads to a PTEN-dependent cell growth defect, highlighting a potential role of POU2AF2-SWI/SNF axis in small cell lung cancer (SCLC) pathogenesis. Additionally, pharmacological inhibition of SWI/SNF phenocopies POU2AF2 depletion in terms of gene expression alteration and cell viability decrease in SCLC-P subtype cells. Therefore, impeding POU2AF2-mediated transcriptional regulation represents a potential therapeutic approach for human SCLC therapy.

Altered metabolome and microbiome associated with compromised intestinal barrier induced hepatic lipid metabolic disorder in mice after subacute and subchronic ozone exposure

Exposure to ozone has been associated with metabolic disorders in humans, but the underlying mechanism remains unclear. In this study, the role of the gut-liver axis and the potential mechanism behind the metabolic disorder were investigated by histological examination, microbiome and metabolome approaches in mice during the subacute (4-week) and subchronic (12-week) exposure to 0.5 ppm and 2.5 ppm ozone. Ozone exposure resulted in slowed weight gain and reduced hepatic lipid contents in a dose-dependent manner. After exposure to ozone, the number of intestinal goblet cells decreased, while the number of tuft cells increased. Tight junction protein zonula occludens-1 (ZO-1) was significantly downregulated, and the apoptosis of epithelial cells increased with compensatory proliferation, indicating a compromised chemical and physical layer of the intestinal barrier. The hepatic and cecal metabolic profiles were altered, primarily related to lipid metabolism and oxidative stress. The abundance of Muribaculaceae increased dose-dependently in both colon and cecum, and was associated with the decrease of metabolites such as bile acids, betaine, and L-carnitine, which subsequently disrupted the intestinal barrier and lipid metabolism. Overall, this study found that subacute and subchronic exposure to ozone induced metabolic disorder via disturbing the gut-liver axis, especially the intestinal barrier. These findings provide new mechanistic understanding of the health risks associated with environmental ozone exposure and other oxidative stressors.

Equine enteroid-derived monolayers recapitulate key features of parasitic intestinal nematode infection

Stem cell-derived organoid cultures have emerged as attractive experimental models for infection biology research regarding various types of gastro-intestinal pathogens and host species. However, the large size of infectious nematode larvae and the closed structure of 3-dimensional organoids often hinder studies of the natural route of infection. To enable easy administration to the apical surface of the epithelium, organoids from the equine small intestine, i.e. enteroids, were used in the present study to establish epithelial monolayer cultures. These monolayers were functionally tested by stimulation with IL-4 and IL-13, and/or exposure to infectious stage larvae of the equine nematodes Parascaris univalens, cyathostominae and/or Strongylus vulgaris. Effects were recorded using transcriptional analysis combined with histochemistry, immunofluorescence-, live-cell- and scanning electron microscopy. These analyses revealed heterogeneous monolayers containing both immature and differentiated cells including tuft cells and mucus-producing goblet cells. Stimulation with IL-4/IL-13 increased tuft- and goblet cell differentiation as demonstrated by the expression of DCLK1 and MUC2. In these cytokine-primed monolayers, the expression of MUC2 was further promoted by co-culture with P. univalens. Moreover, live-cell imaging revealed morphological alterations of the epithelial cells following exposure to larvae even in the absence of cytokine stimulation. Thus, the present work describes the design, characterization and usability of an experimental model representing the equine nematode-infected small intestinal epithelium. The presence of tuft cells and goblet cells whose mucus production is affected by Th2 cytokines and/or the presence of larvae opens up for mechanistic studies of the physical interactions between nematodes and the equine intestinal mucosa.

Expression of FOXI1 and POU2F3 varies among different salivary gland neoplasms and is higher in Warthin tumor

PurposeSalivary gland tumors are histologically diverse. Ionocytes and tuft cells, rare epithelial cells found in normal salivary glands, might be associated with salivary tumors. Here, we explored the expression of FOXI1 and POU2F3, master regulators of ionocytes and tuft cells, respectively, for common salivary neoplasms using immunohistochemistry.MethodsWe analyzed normal salivary tissues and nine salivary gland tumors; Warthin tumors (WT), pleomorphic adenomas (PA), basal cell adenomas, and oncocytomas were benign, whereas mucoepidermoid, adenoid cystic, acinic cell, salivary duct carcinomas, and polymorphous adenocarcinomas were malignant.ResultsNormal salivary glands contained a few FOXI1- and POU2F3-positive cells in the ducts instead of the acini, consistent with ionocytes and tuft cells, respectively. Among the benign tumors, only WTs and PAs consistently expressed FOXI1 (10/10 and 9/10, respectively). The median H-score of WTs was significantly higher than that of PAs (17.5 vs. 4, P = 0.01). While WTs and PAs harbored POU2F3-positive cells (10/10 and 9/10, respectively), the median H-score was higher in WTs than in PAs (10.5 vs 4, respectively). Furthermore, WTs exhibited a unique staining pattern of FOXI1- and POU2F3-positive cells, which were present in luminal and abluminal locations, respectively. Whereas none of the malignant tumors expressed FOXI1, only adenoid cystic carcinoma consistently expressed POU2F3 (5/5), with a median H-score of 4.ConclusionThe expression patterns of the characteristic transcription factors found in ionocytes and tuft cells vary among salivary gland tumor types and are higher in WT, which might be relevant for understanding and diagnosing salivary gland neoplasms.

A45 ASSESSING THE ROLE OF MICROBIOTA DYSBIOSIS ON INTESTINAL TUFT CELL FUNCTIONS UPON GIARDIA INFECTION

Abstract Background Enteric tuft cells can detect and respond to intestinal parasitic infection by modulating host responses to aid parasite clearance, yet the extent of tuft cell functions upon other infections remains to be elucidated. Previous work in our lab showed that the enteric protozoan parasite Giardia induced tuft and goblet cell hyperplasia, yet Giardia colonization in Pou2f3-/- (tuft cell-deficient) mice was impaired. Not only can Giardia modulate the gut microbiota and lead to microbial dysbiosis, but the microbiota itself can influence Giardia colonization. Interestingly, certain microbiota-derived products can activate tuft cells in the gut. In this study, we investigated the role of microbiota dysbiosis in the crosstalk between Giardia and tuft cells. Aims We aim to explore the bidirectional effects between tuft cells and Giardia infection by investigating the role of 1) the host microbiota influenced by the presence or absence of tuft cells in altering Giardia infectivity, and 2) Giardia modified microbiota in contributing to tuft cell activity. Methods Fecal matter from 6–8-week-old C57Bl/6 and Pou2f3-/- mice were administered to polyethylene glycol (PEG) treated C57Bl/6 mice via oral gavage for 7 days, followed by gavage with 5x104Giardia muris trophozoites. Duodenal parasite burden was assessed 11 days after infection. Small intestinal (SI) microbiota was collected from 5–7-week-old C57Bl/6 and Pou2f3-/- mice following 11 days of G. muris infection and transplanted into PEG treated C57Bl/6 and Pou2f3-/- recipients. 11 days post-transfer, SI tuft and goblet cell hyperplasia was assessed in recipient mice by immunohistochemistry, and Dclk1, Atoh1, and Muc2 gene expression was quantified by RT-qPCR. Parameters of gut motility were evaluated. Results FMT with Pou2f3-/- mouse fecal matter prior to Giardia infection led to improved weight gain during infection compared to FMT from C57Bl/6 mice. Giardia modified microbiota (GMM) did not induce tuft or goblet cell hyperplasia 11 days after transfer. Jejunal Dclk1, Atoh1, and Muc2 were no different after GMM compared to control microbiota (CM) transfer. Ileal Atoh1 or Muc2 were upregulated in mice receiving GMM from C57Bl/6 or Pou2f3-/- mice, respectively. Intestinal transit time and stool water content was altered in mice which received GMM from Pou2f3-/- mice compared to CM. Conclusions The resident microbiota in tuft cell deficient mice may in part contribute to limiting Giardia infection. Giardia modified microbiota does not substantially contribute to tuft cell hyperplasia or related gene expression alterations at 11 days after microbiota transfer. The mechanistic contributors to tuft cell hyperplasia during Giardia infection and how a lack of tuft cells can lead to impaired colonization does not appear to be primarily driven by microbiota alterations and remains to be fully defined. Funding Agencies NSERC

A269 SEX-DEPENDENT EFFECT OF PANCREASTATIN INHIBITION ON COLON MUCOSAL INTEGRITY IN HOMEOSTATIC CONDITION

Abstract Background Sex bias in inflammatory bowel disease (IBD)-associated colorectal cancer (CRC) epidemiology is well known. Pancreastatin (PST), an epithelial cells-derived peptide overexpressed in IBD patients, regulates the endoplasmic reticulum (ER) and survival signalling involved in CRC. Pancreastatin inhibitor 8 (PSTi8), an inhibitor of PST, showed promising anti-inflammatory effects in IBD male mice model. However, no data exists regarding PST’s role in colon mucosal regeneration and epithelium maintenance. Aims Here, we investigated the impact of PSTi8 treatment on colonic epithelial cells in male and female mice under homeostatic conditions. Methods Male and female C57BL/6 mice were treated with PSTi8 (2.5mg/mL/kg, i.r.) or PBS for six days. Epithelial cells’ proliferation (Ki67) and differentiation (cytokeratin-20) were measured by immunofluorescence. Genetic markers for differentiated epithelial cells (goblet Muc2 and Tuft Dclk1), stem cells (fast-cycling Lgr5, reserve Hopx and fetal-like Ly6a), stem cell regulator (BMP4), epithelial cells lineage commitment (Atoh1, Hes1, Gfl1), ER activation (ATF6), and apoptosis (CHOP) were tested by qRT-PCR. Results PSTi8 treatment decreased epithelial cell proliferation in both sexes. The inhibition of PST lowered the differentiation of epithelial cells and mucus production and increased tuft cell gene expression in females but not in male mice. In females, PSTi8 treatment increased fast-cycling stem cells but lower reserve and fetal-like stem cells in both sexes. In addition, PST inhibition significantly downregulated BMP4, which regulates epithelial cell differentiation, in females while not altering its expression in males. In contrast, PSTi8 treatment significantly increased transcription factors regulating epithelial cells' self-renewal and lineage commitments Hes1 and GFI1 in females but decreased Atoh1 in both sexes. PST inhibition enhanced gene expression of ER stress molecules ATF6 and CHOP in female and ATF6 in male mice. CHOP remained unaltered by PST inhibition in males. Conclusions PSTi8 alters colonic epithelial regeneration, differentiation, and thus maintenance in a sex-dependent manner. Funding Agencies CIHRChildren’s Hospital Research Institute of Manitoba (CHRIM)/Research Manitoba

Ehf and Fezf2 regulate late medullary thymic epithelial cell and thymic tuft cell development.

Thymic epithelial cells are indispensable for T cell maturation and selection and the induction of central immune tolerance. The self-peptide repertoire expressed by medullary thymic epithelial cells is in part regulated by the transcriptional regulator Aire (Autoimmune regulator) and the transcription factor Fezf2. Due to the high complexity of mTEC maturation stages (i.e., post-Aire, Krt10+ mTECs, and Dclk1+ Tuft mTECs) and the heterogeneity in their gene expression profiles (i.e., mosaic expression patterns), it has been challenging to identify the additional factors complementing the transcriptional regulation. We aimed to identify the transcriptional regulators involved in the regulation of mTEC development and self-peptide expression in an unbiased and genome-wide manner. We used ATAC footprinting analysis as an indirect approach to identify transcription factors involved in the gene expression regulation in mTECs, which we validated by ChIP sequencing. This study identifies Fezf2 as a regulator of the recently described thymic Tuft cells (i.e., Tuft mTECs). Furthermore, we identify that transcriptional regulators of the ELF, ESE, ERF, and PEA3 subfamily of the ETS transcription factor family and members of the Krüppel-like family of transcription factors play a role in the transcriptional regulation of genes involved in late mTEC development and promiscuous gene expression.

A nasal cell atlas reveals heterogeneity of tuft cells and their role in directing olfactory stem cell proliferation.

The olfactory neuroepithelium serves as a sensory organ for odors and forms part of the nasal mucosal barrier. Olfactory sensory neurons are surrounded and supported by epithelial cells. Among them, microvillous cells (MVCs) are strategically positioned at the apical surface, but their specific functions are enigmatic, and their relationship to the other specialized epithelial cells is unclear. Here, we establish that the family of MVCs comprises tuft cells and ionocytes in both mice and humans. Integrating analysis of the respiratory and olfactory epithelia, we define the distinct receptor expression of TRPM5+ tuft-MVCs compared with Gɑ-gustducinhigh respiratory tuft cells and characterize a previously undescribed population of glandular DCLK1+ tuft cells. To establish how allergen sensing by tuft-MVCs might direct olfactory mucosal responses, we used an integrated single-cell transcriptional and protein analysis. Inhalation of Alternaria induced mucosal epithelial effector molecules including Chil4 and a distinct pathway leading to proliferation of the quiescent olfactory horizontal basal stem cell (HBC) pool, both triggered in the absence of olfactory apoptosis. Alternaria- and ATP-elicited HBC proliferation was dependent on TRPM5+ tuft-MVCs, identifying these specialized epithelial cells as regulators of olfactory stem cell responses. Together, our data provide high-resolution characterization of nasal tuft cell heterogeneity and identify a function of TRPM5+ tuft-MVCs in directing the olfactory mucosal response to allergens.