Capicua deficiency induces autoimmunity and promotes follicular helper T cell differentiation via derepression of ETV5

ETV5 reduces androgen receptor expression and induces neural stem-like properties during neuroendocrine prostate cancer development

Neuroendocrine prostate cancer (NEPC), an aggressive subtype induced by hormone therapy, lacks effective treatments. This study explored the role of E26 transformation-specific variant 5 (ETV5) in NEPC development. Analysis of multiple prostate cancer datasets revealed that NEPC is characterized by significantly elevated ETV5 expression compared to other subtypes. ETV5 expression increased progressively under hormone therapy through epigenetic modifications. ETV5 induced neural stem-like features in prostate cancer cells and facilitated their differentiation into NEPC under hormone treatment conditions, both in vitro and in vivo. Our molecular mechanistic study identified PBX3 and TLL1 as target genes of ETV5 that contribute to ETV5 overexpression-induced castration resistance and stemness. Notably, obeticholic acid, identified as an ETV5 inhibitor in this study, exhibited promising efficacy in suppressing NEPC development. This study highlights ETV5 as a key transcription factor that facilitates NEPC development and underscores its potential as a therapeutic target for this aggressive cancer subtype.

The capicua-ataxin-1-like complex regulates Notch-driven marginal zone B cell development and sepsis progression

Follicular B (FOB) and marginal zone B (MZB) cells are pivotal in humoral immune responses against pathogenic infections. MZB cells can exacerbate endotoxic shock via interleukin-6 secretion. Here we show that the transcriptional repressor capicua (CIC) and its binding partner, ataxin-1-like (ATXN1L), play important roles in FOB and MZB cell development. CIC deficiency reduces the size of both FOB and MZB cell populations, whereas ATXN1L deficiency specifically affects MZB cells. B cell receptor signaling is impaired only in Cic-deficient FOB cells, whereas Notch signaling is disrupted in both Cic-deficient and Atxn1l-deficient MZB cells. Mechanistically, ETV4 de-repression leads to inhibition of Notch1 and Notch2 transcription, thereby inhibiting MZB cell development in B cell-specific Cic-deficient (Cicf/f;Cd19-Cre) and Atxn1l-deficient (Atxn1lf/f;Cd19-Cre) mice. In Cicf/f;Cd19-Cre and Atxn1lf/f; Cd19-Cre mice, humoral immune responses and lipopolysaccharide-induced sepsis progression are attenuated but are restored upon Etv4-deletion. These findings highlight the importance of the CIC-ATXN1L complex in MZB cell development and may provide proof of principle for therapeutic targeting in sepsis.

ETV5 promotes lupus pathogenesis and follicular helper T cell differentiation by inducing osteopontin expression

Follicular helper T (TFH) cells mediate germinal center reactions to generate high affinity antibodies against specific pathogens, and their excessive production is associated with the pathogenesis of systemic autoimmune diseases such as systemic lupus erythematosus (SLE). ETV5, a member of the ETS transcription factor family, promotes TFH cell differentiation in mice. In this study, we examined the role of ETV5 in the pathogenesis of lupus in mice and humans. T cell-specific deletion of Etv5 alleles ameliorated TFH cell differentiation and autoimmune phenotypes in lupus mouse models. Further, we identified SPP1 as an ETV5 target that promotes TFH cell differentiation in both mice and humans. Notably, extracellular osteopontin (OPN) encoded by SPP1 enhances TFH cell differentiation by activating the CD44-AKT signaling pathway. Furthermore, ETV5 and SPP1 levels were increased in CD4+ T cells from patients with SLE and were positively correlated with disease activity. Taken together, our findings demonstrate that ETV5 is a lupus-promoting transcription factor, and secreted OPN promotes TFH cell differentiation.

Molecular Determinants of Neurocognitive Deficits in Glioma: Based on 2021 WHO Classification

Cognitive impairment is a common feature among patients with diffuse glioma. The objective of the study is to investigate the relationship between preoperative cognitive function and clinical as well as molecular factors, firstly based on the new 2021 World Health Organization's updated classification of central nervous system tumors. A total of 110 diffuse glioma patients enrolled underwent preoperative cognitive assessments using the Mini-Mental State Examination and Montreal Cognitive Assessment. Clinical information was collected from medical records, and gene sequencing was performed to analyze the 18 most influenced genes. The differences in cognitive function between patients with and without glioblastoma were compared under both the 2016 and 2021 WHO classification of tumors of the central nervous system to assess their effect of differentiation on cognition. The study found that age, tumor location, and glioblastoma had significant differences in cognitive function. Several genetic alterations were significantly correlated with cognition. Especially, IDH, CIC, and ATRX are positively correlated with several cognitive domains, while most other genes are negatively correlated. For most focused genes, patients with a low number of genetic alterations tended to have better cognitive function. Our study suggested that, in addition to clinical characteristics such as age, histological type, and tumor location, molecular characteristics play a crucial role in cognitive function. Further research into the mechanisms by which tumors affect brain function is expected to enhance the quality of life for glioma patients. This study highlights the importance of considering both clinical and molecular factors in the management of glioma patients to improve cognitive outcomes.

Integrated molecular and immunological features of human T-lymphotropic virus type 1 infection and disease progression to adult T-cell leukaemia or lymphoma

The human T-lymphotropic virus type 1 (HTLV-1) retrovirus infects 10-20 million people globally, with endemic regions in southwestern Japan, the Caribbean basin, Africa, and central Australia. HTLV-1 is associated with lifelong infection and immune suppression, resulting in a range of serious sequalae, including adult T-cell leukaemia or lymphoma (ATLL) in 5% of cases. To date, there are no preventive or curative treatments for HTLV-1 and treatment outcomes for ATLL remain generally poor. Depending on the disease subtype, overall survival is 8-55 months. Recent advancements in the past decade have identified genetic, molecular, and immunological events occurring throughout the lives of individuals infected with HTLV-1 and of those who progress to ATLL. In addition, updated guidelines for clinical management have been published. With the aim of focusing research efforts on the development of treatments for both HTLV-1 infections and ATLL, we have conceptualised a four-step disease model for HTLV-1-associated ATLL: (1) viral exposure, (2) establishment of chronic infection, (3) cellular transformation and evolution, and (4) disease presentation and management. For each stage we describe the clinical features, molecular and immunological factors involved, potential biomarkers of disease progression, and the therapeutic applicability of individual targets. We also discuss emerging concepts and novel treatment approaches. Our hope is that this model will promote research interest and guide the testing of new treatments for this neglected virus and its associated rare cancer.

Inside-out assembly of viral antigens for the enhanced vaccination

Current attempts in vaccine delivery systems concentrate on replicating the natural dissemination of live pathogens, but neglect that pathogens evolve to evade the immune system rather than to provoke it. In the case of enveloped RNA viruses, it is the natural dissemination of nucleocapsid protein (NP, core antigen) and surface antigen that delays NP exposure to immune surveillance. Here, we report a multi-layered aluminum hydroxide-stabilized emulsion (MASE) to dictate the delivery sequence of the antigens. In this manner, the receptor-binding domain (RBD, surface antigen) of the spike protein was trapped inside the nanocavity, while NP was absorbed on the outside of the droplets, enabling the burst release of NP before RBD. Compared with the natural packaging strategy, the inside-out strategy induced potent type I interferon-mediated innate immune responses and triggered an immune-potentiated environment in advance, which subsequently boosted CD40⁺ DC activations and the engagement of the lymph nodes. In both H1N1 influenza and SARS-CoV-2 vaccines, rMASE significantly increased antigen-specific antibody secretion, memory T cell engagement, and Th1-biased immune response, which diminished viral loads after lethal challenge. By simply reversing the delivery sequence of the surface antigen and core antigen, the inside-out strategy may offer major implications for enhanced vaccinations against the enveloped RNA virus.

Multi-Omic Analysis of CIC's Functional Networks Reveals Novel Interaction Partners and a Potential Role in Mitotic Fidelity

CIC encodes a transcriptional repressor and MAPK signalling effector that is inactivated by loss-of-function mutations in several cancer types, consistent with a role as a tumour suppressor. Here, we used bioinformatic, genomic, and proteomic approaches to investigate CIC's interaction networks. We observed both previously identified and novel candidate interactions between CIC and SWI/SNF complex members, as well as novel interactions between CIC and cell cycle regulators and RNA processing factors. We found that CIC loss is associated with an increased frequency of mitotic defects in human cell lines and an in vivo mouse model and with dysregulated expression of mitotic regulators. We also observed aberrant splicing in CIC-deficient cell lines, predominantly at 3' and 5' untranslated regions of genes, including genes involved in MAPK signalling, DNA repair, and cell cycle regulation. Our study thus characterises the complexity of CIC's functional network and describes the effect of its loss on cell cycle regulation, mitotic integrity, and transcriptional splicing, thereby expanding our understanding of CIC's potential roles in cancer. In addition, our work exemplifies how multi-omic, network-based analyses can be used to uncover novel insights into the interconnected functions of pleiotropic genes/proteins across cellular contexts.

E26 transformation-specific transcription variant 5 in development and cancer: modification, regulation and function

E26 transformation-specific (ETS) transcription variant 5 (ETV5), also known as ETS-related molecule (ERM), exerts versatile functions in normal physiological processes, including branching morphogenesis, neural system development, fertility, embryonic development, immune regulation, and cell metabolism. In addition, ETV5 is repeatedly found to be overexpressed in multiple malignant tumors, where it is involved in cancer progression as an oncogenic transcription factor. Its roles in cancer metastasis, proliferation, oxidative stress response and drug resistance indicate that it is a potential prognostic biomarker, as well as a therapeutic target for cancer treatment. Post-translational modifications, gene fusion events, sophisticated cellular signaling crosstalk and non-coding RNAs contribute to the dysregulation and abnormal activities of ETV5. However, few studies to date systematically summarized the role and molecular mechanisms of ETV5 in benign diseases and in oncogenic progression. In this review, we specify the molecular structure and post-translational modifications of ETV5. In addition, its critical roles in benign and malignant diseases are summarized to draw a panorama for specialists and clinicians. The updated molecular mechanisms of ETV5 in cancer biology and tumor progression are delineated. Finally, we prospect the further direction of ETV5 research in oncology and its potential translational applications in the clinic.

ERK phosphorylation disrupts the intramolecular interaction of capicua to promote cytoplasmic translocation of capicua and tumor growth

Activation of receptor tyrosine kinase signaling inactivates capicua (CIC), a transcriptional repressor that functions as a tumor suppressor, via degradation and/or cytoplasmic translocation. Although CIC is known to be inactivated by phosphorylation, the mechanisms underlying the cytoplasmic translocation of CIC remain poorly understood. Therefore, we aimed to evaluate the roles of extracellular signal-regulated kinase (ERK), p90RSK, and c-SRC in the epidermal growth factor receptor (EGFR) activation-induced cytoplasmic translocation of CIC and further investigated the molecular basis for this process. We found that nuclear ERK induced the cytoplasmic translocation of CIC-S. We identified 12 serine and threonine (S/T) residues within CIC, including S173 and S301 residues that are phosphorylated by p90RSK, which contribute to the cytoplasmic translocation of CIC-S when phosphorylated. The amino-terminal (CIC-S-N) and carboxyl-terminal (CIC-S-C) regions of CIC-S were found to interact with each other to promote their nuclear localization. EGF treatment disrupted the interaction between CIC-S-N and CIC-S-C and induced their cytoplasmic translocation. Alanine substitution for the 12 S/T residues blocked the cytoplasmic translocation of CIC-S and consequently enhanced the tumor suppressor activity of CIC-S. Our study demonstrates that ERK-mediated disruption of intramolecular interaction of CIC is critical for the cytoplasmic translocation of CIC, and suggests that the nuclear retention of CIC may represent a strategy for cancer therapy.

The effects of rhein on D-GalN/LPS-induced acute liver injury in mice: Results from gut microbiome-metabolomics and host transcriptome analysis

Background

Rhubarb is an important traditional Chinese medicine, and rhein is one of its most important active ingredients. Studies have found that rhein can improve ulcerative colitis by regulating gut microbes, but there are few reports on its effects on liver diseases. Therefore, this study aims to investigate these effects and underlying mechanisms.

Methods

Mice were given rhein (100 mg/kg), with both a normal control group and a model group receiving the same amount of normal saline for one week. Acute liver injury was induced in mice by intraperitoneal injection of D-GalN (800 mg/kg)/LPS (10 ug/kg). Samples (blood, liver, and stool) were then collected and assessed for histological lesions and used for 16S rRNA gene sequencing, high-performance liquid chromatography-mass spectrometry (LC-MS) and RNA-seq analysis.

Results

The levels of ALT and AST in the Model group were abnormal higher compared to the normal control group, and the levels of ALT and AST were significantly relieved in the rhein group. Hepatic HE staining showed that the degree of liver injury in the rhein group was lighter than that in the model group, and microbiological results showed that norank_o:Clostridia_UCG-014, Lachnoclostridium, and Roseburia were more abundant in the model group compared to the normal control group. Notably, the rhein treatment group showed reshaped disturbance of intestinal microbial community by D-GalN/LPS and these mice also had higher levels of Verrucomicrobia, Akkermansiaceae and Bacteroidetes. Additionally, There were multiple metabolites that were significantly different between the normal control group and the model group, such as L-α-amino acid, ofloxacin-N-oxide, 1-hydroxy-1,3-diphenylpropan-2-one,and L-4-hydroxyglutamate semialdehyde, but that returned to normal levels after rhein treatment. The gene expression level in the model group also changed significantly, various genes such as Cxcl2, S100a9, Tnf, Ereg, and IL-10 were up-regulated, while Mfsd2a and Bhlhe41 were down-regulated, which were recovered after rhein treatment.

Conclusion

Overall, our results show that rhein alleviated D-GalN/LPS-induced acute liver injury in mice. It may help modulate gut microbiota in mice, thereby changing metabolism in the intestine. Meanwhile, rhein also may help regulate genes expression level to alleviate D-GalN/LPS-induced acute liver injury.

Early fish domestication affects methylation of key genes involved in the rapid onset of the farmed phenotype

Animal domestication is a process of environmental modulation and artificial selection leading to permanent phenotypic modifications. Recent studies showed that phenotypic changes occur very early in domestication, i.e., within the first generation in captivity, which raises the hypothesis that epigenetic mechanisms may play a critical role on the early onset of the domestic phenotype. In this context, we applied reduced representation bisulphite sequencing to compare methylation profiles between wild Nile tilapia females and their offspring reared under farmed conditions. Approximately 700 differentially methylated CpG sites were found, many of them associated not only with genes involved in muscle growth, immunity, autophagy and diet response but also related to epigenetic mechanisms, such as RNA methylation and histone modifications. This bottom-up approach showed that the phenotypic traits often related to domestic animals (e.g., higher growth rate and different immune status) may be regulated epigenetically and prior to artificial selection on gene sequences. Moreover, it revealed the importance of diet in this process, as reflected by differential methylation patterns in genes critical to fat metabolism. Finally, our study highlighted that the TGF-β1 signalling pathway may regulate and be regulated by several differentially methylated CpG-associated genes. This could be an important and multifunctional component in promoting adaptation of fish to a domestic environment while modulating growth and immunity-related traits.

Generation of hematopoietic lineage cell-specific chimeric mice using retrovirus-transduced fetal liver cells

Hematopoietic lineage cell-specific transgenic or knockout mice provide a valuable platform to identify the role of specific genes in hematopoiesis in vivo. Here, we describe protocols for preparation of retroviruses for overexpression or knockdown of a gene of interest, retroviral transduction of fetal liver cells, and generation of hematopoietic lineage cell-specific chimeric mice by transfer of the retrovirus-transduced fetal liver cells. This protocol is applicable for the study of in vivo functionality of a gene of interest in immune cells.

For complete details on the use and execution of this protocol, please refer to Chang et al. (2013), Lee et al. (2016), and Hong et al. (2022).

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Preparation of retroviruses for overexpression or knockdown of a gene of interest

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Retroviral transduction of E15.5 fetal liver cells

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Generation of chimeric mice by transfer of the retroviral transduced fetal liver cells

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Study of in vivo functionality of a gene of interest in immune cells

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Whole-genome landscape of adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) is an aggressive neoplasm immunophenotypically resembling regulatory T cells, associated with human T-cell leukemia virus type-1. Here, we performed whole-genome sequencing (WGS) of 150 ATL cases to reveal the overarching landscape of genetic alterations in ATL. We discovered frequent (33%) loss-of-function alterations preferentially targeting the CIC long isoform, which were overlooked by previous exome-centric studies of various cancer types. Long but not short isoform-specific inactivation of Cic selectively increased CD4+CD25+Foxp3+ T cells in vivo. We also found recurrent (13%) 3'-truncations of REL, which induce transcriptional upregulation and generate gain-of-function proteins. More importantly, REL truncations are also common in diffuse large B-cell lymphoma, especially in germinal center B-cell-like subtype (12%). In the non-coding genome, we identified recurrent mutations in regulatory elements, particularly splice sites, of several driver genes. In addition, we characterized the different mutational processes operative in clustered hypermutation sites within and outside immunoglobulin/T-cell receptor genes and identified the mutational enrichment at the binding sites of host and viral transcription factors, suggesting their activities in ATL. By combining the analyses for coding and noncoding mutations, structural variations, and copy number alterations, we discovered 56 recurrently altered driver genes, including 11 novel ones. Finally, ATL cases were classified into 2 molecular groups with distinct clinical and genetic characteristics based on the driver alteration profile. Our findings not only help to improve diagnostic and therapeutic strategies in ATL, but also provide insights into T-cell biology and have implications for genome-wide cancer driver discovery.

Postnatal regulation of B-1a cell development and survival by the CIC-PER2-BHLHE41 axis

B-1 cell development mainly occurs via fetal and neonatal hematopoiesis and is suppressed in adult bone marrow hematopoiesis. However, little is known about the factors inhibiting B-1 cell development at the adult stage. We report that capicua (CIC) suppresses postnatal B-1a cell development and survival. CIC levels are high in B-1a cells and gradually increase in transitional B-1a (TrB-1a) cells with age. B-cell-specific Cic-null mice exhibit expansion of the B-1a cell population and a gradual increase in TrB-1a cell frequency with age but attenuated B-2 cell development. CIC deficiency enhances B cell receptor (BCR) signaling in transitional B cells and B-1a cell viability. Mechanistically, CIC-deficiency-mediated Per2 derepression upregulates Bhlhe41 levels by inhibiting CRY-mediated transcriptional repression for Bhlhe41, consequently promoting B-1a cell formation in Cic-null mice. Taken together, CIC is a key transcription factor that limits the B-1a cell population at the adult stage and balances B-1 versus B-2 cell formation.

Regulation of positive and negative selection and TCR signaling during thymic T cell development by capicua

Central tolerance is achieved through positive and negative selection of thymocytes mediated by T cell receptor (TCR) signaling strength. Thus, dysregulation of the thymic selection process often leads to autoimmunity. Here, we show that Capicua (CIC), a transcriptional repressor that suppresses autoimmunity, controls the thymic selection process. Loss of CIC prior to T-cell lineage commitment impairs both positive and negative selection of thymocytes. CIC deficiency attenuated TCR signaling in CD4⁺CD8⁺ double-positive (DP) cells, as evidenced by a decrease in CD5 and phospho-ERK levels and calcium flux. We identified Spry4, Dusp4, Dusp6, and Spred1 as CIC target genes that could inhibit TCR signaling in DP cells. Furthermore, impaired positive selection and TCR signaling were partially rescued in Cic and Spry4 double mutant mice. Our findings indicate that CIC is a transcription factor required for thymic T cell development and suggests that CIC acts at multiple stages of T cell development and differentiation to prevent autoimmunity.

Integrative multi-omic analysis reveals neurodevelopmental gene dysregulation in CIC-knockout and IDH1 mutant cells

Capicua (CIC)'s transcriptional repressor function is implicated in neurodevelopment and in oligodendroglioma (ODG) aetiology. However, CIC's role in these contexts remains obscure, primarily from our currently limited knowledge regarding its biological functions. Moreover, CIC mutations in ODG invariably co‐occur with a neomorphic IDH1/2 mutation, yet the functional relationship between these two genetic events is unknown. Here, we analysed models derived from an E6/E7/hTERT‐immortalized (i.e. p53‐ and RB‐deficient) normal human astrocyte cell line. To examine the consequences of CIC loss, we compared transcriptomic and epigenomic profiles between CIC wild‐type and knockout cell lines, with and without mutant IDH1 expression. Our analyses revealed dysregulation of neurodevelopmental genes in association with CIC loss. CIC ChIP‐seq was also performed to expand upon the currently limited ensemble of known CIC target genes. Among the newly identified direct CIC target genes were EPHA2 and ID1, whose functions are linked to neurodevelopment and the tumourigenicity of in vivo glioma tumour models. NFIA, a known mediator of gliogenesis, was discovered to be uniquely overexpressed in CIC‐knockout cells expressing mutant IDH1‐R132H protein. These results identify neurodevelopment and specific genes within this context as candidate targets through which CIC alterations may contribute to the progression of IDH‐mutant gliomas. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Construction of a prognostic immune signature for lower grade glioma that can be recognized by MRI radiomics features to predict survival in LGG patients

BACKGROUND

This study aimed to identify a series of prognostically relevant immune features by immunophenoscore. Immune features were explored using MRI radiomics features to prediction the overall survival (OS) of lower-grade glioma (LGG) patients and their response to immune checkpoints.

METHOD

LGG data were retrieved from TCGA and categorized into training and internal validation datasets. Patients attending the First Affiliated Hospital of Harbin Medical University were included in an external validation cohort. An immunophenoscore-based signature was built to predict malignant potential and response to immune checkpoint inhibitors in LGG patients. In addition, a deep learning neural network prediction model was built for validation of the immunophenoscore-based signature.

RESULTS

Immunophenotype-associated mRNA signatures (IMriskScore) for outcome prediction and ICB therapeutic effects in LGG patients were constructed. Deep learning of neural networks based on radiomics showed that MRI radiomic features determined IMriskScore. Enrichment analysis and ssGSEA correlation analysis were performed. Mutations in CIC significantly improved the prognosis of patients in the high IMriskScore group. Therefore, CIC is a potential therapeutic target for patients in the high IMriskScore group. Moreover, IMriskScore is an independent risk factor that can be used clinically to predict LGG patient outcomes.

CONCLUSIONS

The IMriskScore model consisting of a sets of biomarkers, can independently predict the prognosis of LGG patients and provides a basis for the development of personalized immunotherapy strategies. In addition, IMriskScore features were predicted by MRI radiomics using a deep learning approach using neural networks. Therefore, they can be used for the prognosis of LGG patients.

Interaction between γδTCR signaling and the E protein-Id axis in γδ T cell development

γδ T cells acquire their functional properties in the thymus, enabling them to exert rapid innate-like responses. To understand how distinct γδ T cell subsets are generated, we have developed a Two-Stage model for γδ T cell development. This model is predicated on the finding that γδTCR signal strength impacts E protein activity through graded upregulation of Id3. Our model proposes that cells enter Stage 1 in response to a γδTCR signaling event in the cortex that activates a γδ T cell-specific gene network. Part of this program includes the upregulation of chemokine receptors that guide them to the medulla. In the medulla, Stage 1 cells receive distinct combinations of γδTCR, cytokine, and/co-stimulatory signals that induce their transit into Stage 2, either toward the γδT1 or the γδT17 lineage. The intersection between γδTCR and cytokine signals can tune Id3 expression, leading to different outcomes even in the presence of strong γδTCR signals. The thymic signaling niches required for γδT17 development are segregated in time and space, providing transient windows of opportunity during ontogeny. Understanding the regulatory context in which E proteins operate at different stages will be key in defining how their activity levels impose functional outcomes.

Deletion Timing of Cic Alleles during Hematopoiesis Determines the Degree of Peripheral CD4+ T Cell Activation and Proliferation

Capicua (CIC) is a transcriptional repressor that regulates several developmental processes. CIC deficiency results in lymphoproliferative autoimmunity accompanied by expansion of CD44hiCD62Llo effector/memory and follicular Th cell populations. Deletion of Cic alleles in hematopoietic stem cells (Vav1-Cre-mediated knockout of Cic) causes more severe autoimmunity than that caused by the knockout of Cic in CD4+CD8+ double positive thymocytes (Cd4-Cre-mediated knockout of Cic). In this study, we compared splenic CD4+ T cell activation and proliferation between whole immune cell-specific Cic-null (Cicf/f;Vav1-Cre) and T cell-specific Cic-null (Cicf/f;Cd4-Cre) mice. Hyperactivation and hyperproliferation of CD4+ T cells were more apparent in Cicf/f;Vav1-Cre mice than in Cicf/f;Cd4-Cre mice. Cicf/f;Vav1-Cre CD4+ T cells more rapidly proliferated and secreted larger amounts of IL-2 upon TCR stimulation than did Cicf/f;Cd4-Cre CD4+ T cells, while the TCR stimulation-induced activation of the TCR signaling cascade and calcium flux were comparable between them. Mixed wild-type and Cicf/f;Vav1-Cre bone marrow chimeras also exhibited more apparent hyperactivation and hyperproliferation of Cic-deficient CD4+ T cells than did mixed wild-type and Cicf/f;Cd4-Cre bone marrow chimeras. Taken together, our data demonstrate that CIC deficiency at the beginning of T cell development endows peripheral CD4+ T cells with enhanced T cell activation and proliferative capability.

Ataxin-1 regulates B cell function and the severity of autoimmune experimental encephalomyelitis

Ataxin-1 (ATXN1) is a ubiquitous polyglutamine protein expressed primarily in the nucleus where it binds chromatin and functions as a transcriptional repressor. Mutant forms of ataxin-1 containing expanded glutamine stretches cause the movement disorder spinocerebellar ataxia type 1 (SCA1) through a toxic gain-of-function mechanism in the cerebellum. Conversely, ATXN1 loss-of-function is implicated in cancer development and Alzheimer's disease (AD) pathogenesis. ATXN1 was recently nominated as a susceptibility locus for multiple sclerosis (MS). Here, we show that Atxn1-null mice develop a more severe experimental autoimmune encephalomyelitis (EAE) course compared to wildtype mice. The aggravated phenotype is mediated by increased T helper type 1 (Th1) cell polarization, which in turn results from the dysregulation of B cell activity. Ataxin-1 ablation in B cells leads to aberrant expression of key costimulatory molecules involved in proinflammatory T cell differentiation, including cluster of differentiation (CD)44 and CD80. In addition, comprehensive phosphoflow cytometry and transcriptional profiling link the exaggerated proliferation of ataxin-1 deficient B cells to the activation of extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription (STAT) pathways. Lastly, selective deletion of the physiological binding partner capicua (CIC) demonstrates the importance of ATXN1 native interactions for correct B cell functioning. Altogether, we report a immunomodulatory role for ataxin-1 and provide a functional description of the ATXN1 locus genetic association with MS risk.

CIC de novo loss of function variants contribute to cerebral folate deficiency by downregulating FOLR1 expression

Background Cerebral folate deficiency (CFD) syndrome is characterised by a low concentration of 5-methyltetrahydrofolate in cerebrospinal fluid, while folate levels in plasma and red blood cells are in the low normal range. Mutations in several folate pathway genes, including FOLR1 (folate receptor alpha, FRα), DHFR (dihydrofolate reductase) and PCFT (proton coupled folate transporter) have been previously identified in patients with CFD.

Methods In an effort to identify causal mutations for CFD, we performed whole exome sequencing analysis on eight CFD trios and identified eight de novo mutations in seven trios.

Results Notably, we found a de novo stop gain mutation in the capicua (CIC) gene. Using 48 sporadic CFD samples as a validation cohort, we identified three additional rare variants in CIC that are putatively deleterious mutations. Functional analysis indicates that CIC binds to an octameric sequence in the promoter regions of folate transport genes: FOLR1, PCFT and reduced folate carrier (Slc19A1; RFC1). The CIC nonsense variant (p.R353X) downregulated FOLR1 expression in HeLa cells as well as in the induced pluripotent stem cell (iPSCs) derived from the original CFD proband. Folate binding assay demonstrated that the p.R353X variant decreased cellular binding of folic acid in cells.

Conclusion This study indicates that CIC loss of function variants can contribute to the genetic aetiology of CFD through regulating FOLR1 expression. Our study described the first mutations in a non-folate pathway gene that can contribute to the aetiology of CFD.

CIC is a critical regulator of neuronal differentiation

Capicua (CIC), a member of the high mobility group-box (HMG-box) superfamily of transcriptional repressors, is frequently mutated in human oligodendrogliomas. However, its functions in brain development and tumorigenesis remain poorly understood. Here, we report that brain-specific deletion of Cic compromises developmental transition of neuroblasts to immature neurons in mouse hippocampus and compromises normal neuronal differentiation. Combined gene expression and ChIP-seq analyses identified VGF as an important CIC-repressed transcriptional surrogate involved in neuronal lineage regulation. Aberrant VGF expression promotes neural progenitor cell proliferation by suppressing their differentiation. Mechanistically, we demonstrated that CIC represses VGF expression by tethering SIN3-HDAC to form a transcriptional corepressor complex. Mass spectrometry analysis of CIC-interacting proteins further identified the BRG1-containing mSWI/SNF complex whose function is necessary for transcriptional repression by CIC. Together, this study uncovers a potentially novel regulatory pathway of CIC-dependent neuronal differentiation and may implicate these molecular mechanisms in CIC-dependent brain tumorigenesis.

Regulation and function of capicua in mammals

Capicua (CIC) is an evolutionarily conserved transcription factor. CIC contains a high-mobility group (HMG) box that recognizes specific DNA sequences to regulate the expression of various target genes. CIC was originally identified in Drosophila melanogaster as a transcriptional repressor that suppresses the receptor tyrosine kinase signaling pathway. This molecule controls normal organ growth and tissue patterning as well as embryogenesis in Drosophila. Recent studies have also demonstrated its extensive functions in mammals. For example, CIC regulates several developmental and physiological processes, including lung development, abdominal wall closure during embryogenesis, brain development and function, neural stem cell homeostasis, T cell differentiation, and enterohepatic circulation of bile acids. CIC is also associated with the progression of various types of cancer and neurodegeneration in spinocerebellar ataxia type-1, systemic autoimmunity, and liver injury. In this review, I provide a broad overview of our current understanding of the regulation and functions of CIC in mammals and discuss future research directions.

Capicua restricts cancer stem cell-like properties in breast cancer cells

Cancer stem cells (CSCs) play a central role in cancer initiation, progression, therapeutic resistance, and recurrence in patients. Here we present Capicua (CIC), a developmental transcriptional repressor, as a suppressor of CSC properties in breast cancer cells. CIC deficiency critically enhances CSC self-renewal and multiple CSC subpopulations of breast cancer cells without altering their growth rate or invasiveness. Loss of CIC relieves repression of ETV4 and ETV5 expression, consequently promoting self-renewal capability, EpCAM⁺/CD44⁺/CD24^low/- expression, and ALDH activity. In xenograft models, CIC deficiency significantly increases CSC frequency and drives tumor initiation through derepression of ETV4. Consistent with the experimental data, the CD44^high/CD24^low CSC-like feature is inversely correlated with CIC levels in breast cancer patients. We also identify SOX2 as a downstream target gene of CIC that partly promotes CSC properties. Taken together, our study demonstrates that CIC suppresses breast cancer formation via restricting cancer stemness and proposes CIC as a potential regulator of stem cell maintenance.

Capicua suppresses colorectal cancer progression via repression of ETV4 expression

Background

Although major driver gene mutations have been identified, the complex molecular heterogeneity of colorectal cancer (CRC) remains unclear. Capicua (CIC) functions as a tumor suppressor in various types of cancers; however, its role in CRC progression has not been examined.

Methods

Databases for gene expression profile in CRC patient samples were used to evaluate the association of the levels of CIC and Polyoma enhancer activator 3 (PEA3) group genes (ETS translocation variant 1 (ETV1), ETV4, and ETV5), the best-characterized CIC targets in terms of CIC functions, with clinicopathological features of CRC. CIC and ETV4 protein levels were also examined in CRC patient tissue samples. Gain- and loss-of function experiments in cell lines and mouse xenograft models were performed to investigate regulatory functions of CIC and ETV4 in CRC cell growth and invasion. qRT-PCR and western blot analyses were performed to verify the CIC regulation of ETV4 expression in CRC cells. Rescue experiments were conducted using siRNA against ETV4 and CIC-deficient CRC cell lines.

Results

CIC expression was decreased in the tissue samples of CRC patients. Cell invasion, migration, and proliferation were enhanced in CIC-deficient CRC cells and suppressed in CIC-overexpressing cells. Among PEA3 group genes, ETV4 levels were most dramatically upregulated and inversely correlated with the CIC levels in CRC patient samples. Furthermore, derepression of ETV4 was more prominent in CIC-deficient CRC cells, when compared with that observed for ETV1 and ETV5. The enhanced cell proliferative and invasive capabilities in CIC-deficient CRC cells were completely recovered by knockdown of ETV4.

Conclusion

Collectively, the CIC-ETV4 axis is not only a key module that controls CRC progression but also a novel therapeutic and/or diagnostic target for CRC.

Genome-wide CRISPR/Cas9 Screen Identifies Host Factors Essential for Influenza Virus Replication

The emergence of influenza A viruses (IAVs) from zoonotic reservoirs poses a great threat to human health. As seasonal vaccines are ineffective against zoonotic strains, and newly transmitted viruses can quickly acquire drug resistance, there remains a need for host-directed therapeutics against IAVs. Here, we performed a genome-scale CRISPR/Cas9 knockout screen in human lung epithelial cells with a human isolate of an avian H5N1 strain. Several genes involved in sialic acid biosynthesis and related glycosylation pathways were highly enriched post-H5N1 selection, including SLC35A1, a sialic acid transporter essential for IAV receptor expression and thus viral entry. Importantly, we have identified capicua (CIC) as a negative regulator of cell-intrinsic immunity, as loss of CIC resulted in heightened antiviral responses and restricted replication of multiple viruses. Therefore, our study demonstrates that the CRISPR/Cas9 system can be utilized for the discovery of host factors critical for the replication of intracellular pathogens.

The Capicua tumor suppressor: a gatekeeper of Ras signaling in development and cancer

The transcriptional repressor Capicua (CIC) has emerged as an important rheostat of cell growth regulated by RAS/MAPK signaling. Cic was originally discovered in Drosophila, where it was shown to be inactivated by MAPK signaling downstream of the RTKs Torso and EGFR, which results in signal-dependent responses that are required for normal cell fate specification, proliferation and survival of developing and adult tissues. CIC is highly conserved in mammals, where it is also negatively regulated by MAPK signaling. Here, we review the roles of CIC during mammalian development, tissue homeostasis, tumor formation and therapy resistance. Available data indicate that CIC is involved in multiple biological processes, including lung development, liver homeostasis, autoimmunity and neurobehavioral processes. Moreover, CIC has been shown to be involved in tumor development as a tumor suppressor, both in human as well as in mouse models. Finally, several lines of evidence implicate CIC as a determinant of sensitivity to EGFR and MAPK pathway inhibitors, suggesting that CIC may play a broader role in human cancer than originally anticipated.

The Capicua/ETS Translocation Variant 5 Axis Regulates Liver-Resident Memory CD8+ T-Cell Development and the Pathogenesis of Liver Injury

Liver-resident memory T (liver T_RM ) cells exert protective immune responses following liver infection by malaria parasites. However, how these T_RM cells are developed and what the consequence is if they are not properly maintained remain poorly understood. Here, we show that the transcriptional repressor, Capicua (CIC), controls liver CD8⁺ T_RM cell development to maintain normal liver function. Cic-deficient mice have a greater number of liver CD8⁺ T_RM cells and liver injury phenotypes accompanied by increased levels of proinflammatory cytokine genes in liver tissues. Excessive formation of CD69⁺ CD8⁺ T_RM -like cells was also observed in mice with acetaminophen-induced liver injury (AILI). Moreover, expansion of liver CD8⁺ T_RM cell population and liver injury phenotypes in T-cell-specific Cic null mice were rescued by codeletion of ETS translocation variant [Etv]5 alleles, indicating that Etv5 is a CIC target gene responsible for regulation of CD8⁺ T_RM cell development and liver function. We also discovered that ETV5 directly regulates expression of Hobit, a master transcription factor for T_RM cell development, in CD8⁺ T cells. Conclusion: Our findings suggest the CIC-ETV5 axis as a key molecular module that controls CD8⁺ T_RM cell development, indicating a pathogenic role for CD8⁺ T_RM cells in liver injury.

The Transcription Factor Ets1 Suppresses T Follicular Helper Type 2 Cell Differentiation to Halt the Onset of Systemic Lupus Erythematosus

Single-nucleotide polymorphisms in ETS1 are associated with systemic lupus erythematosus (SLE). Ets1-/- mice develop SLE-like symptoms, suggesting that dysregulation of this transcription factor is important to the onset or progression of SLE. We used conditional deletion approaches to examine the impact of Ets1 expression in different immune cell types. Ets1 deletion on CD4+ T cells, but not B cells or dendritic cells, resulted in the SLE autoimmunity, and this was associated with the spontaneous expansion of T follicular helper type 2 (Tfh2) cells. Ets1-/- Tfh2 cells exhibited increased expression of GATA-3 and interleukin-4 (IL-4), which induced IgE isotype switching in B cells. Neutralization of IL-4 reduced Tfh2 cell frequencies and ameliorated disease parameters. Mechanistically, Ets1 suppressed signature Tfh and Th2 cell genes, including Cxcr5, Bcl6, and Il4ra, thus curbing the terminal Tfh2 cell differentiation process. Tfh2 cell frequencies in SLE patients correlated with disease parameters, providing evidence for the relevance of these findings to human disease.

The Tumor Suppressor CIC Directly Regulates MAPK Pathway Genes via Histone Deacetylation

Oligodendrogliomas are brain tumors accounting for approximately 10% of all central nervous system cancers. CIC is a transcription factor that is mutated in most patients with oligodendrogliomas; these mutations are believed to be a key oncogenic event in such cancers. Analysis of the Drosophila melanogaster ortholog of CIC, Capicua, indicates that CIC loss phenocopies activation of the EGFR/RAS/MAPK pathway, and studies in mammalian cells have demonstrated a role for CIC in repressing the transcription of the PEA3 subfamily of ETS transcription factors. Here, we address the mechanism by which CIC represses transcription and assess the functional consequences of CIC inactivation. Genome-wide binding patterns of CIC in several cell types revealed that CIC target genes were enriched for MAPK effector genes involved in cell-cycle regulation and proliferation. CIC binding to target genes was abolished by high MAPK activity, which led to their transcriptional activation. CIC interacted with the SIN3 deacetylation complex and, based on our results, we suggest that CIC functions as a transcriptional repressor through the recruitment of histone deacetylases. Independent single amino acid substitutions found in oligodendrogliomas prevented CIC from binding its target genes. Taken together, our results show that CIC is a transcriptional repressor of genes regulated by MAPK signaling, and that ablation of CIC function leads to increased histone acetylation levels and transcription at these genes, ultimately fueling mitogen-independent tumor growth.Significance: Inactivation of CIC inhibits its direct repression of MAPK pathway genes, leading to their increased expression and mitogen-independent growth.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/15/4114/F1.large.jpg Cancer Res; 78(15); 4114-25. ©2018 AACR.

Capicua suppresses hepatocellular carcinoma progression by controlling the ETV4-MMP1 axis

Hepatocellular carcinoma (HCC) is developed by multiple steps accompanying progressive alterations of gene expression, which leads to increased cell proliferation and malignancy. Although environmental factors and intracellular signaling pathways that are critical for HCC progression have been identified, gene expression changes and the related genetic factors contributing to HCC pathogenesis are still insufficiently understood. In this study, we identify a transcriptional repressor, Capicua (CIC), as a suppressor of HCC progression and a potential therapeutic target. Expression of CIC is posttranscriptionally reduced in HCC cells. CIC levels are correlated with survival rates in patients with HCC. CIC overexpression suppresses HCC cell proliferation and invasion, whereas loss of CIC exerts opposite effects in vivo as well as in vitro. Levels of polyoma enhancer activator 3 (PEA3) group genes, the best-known CIC target genes, are correlated with lethality in patients with HCC. Among the PEA3 group genes, ETS translocation variant 4 (ETV4) is the most significantly up-regulated in CIC-deficient HCC cells, consequently promoting HCC progression. Furthermore, it induces expression of matrix metalloproteinase 1 (MMP1), the MMP gene highly relevant to HCC progression, in HCC cells; and knockdown of MMP1 completely blocks the CIC deficiency-induced HCC cell proliferation and invasion.

CONCLUSION

Our study demonstrates that the CIC-ETV4-MMP1 axis is a regulatory module controlling HCC progression. (Hepatology 2018;67:2287-2301).

ATXN1-CIC Complex Is the Primary Driver of Cerebellar Pathology in Spinocerebellar Ataxia Type 1 through a Gain-of-Function Mechanism

Polyglutamine (polyQ) diseases are caused by expansion of translated CAG repeats in distinct genes leading to altered protein function. In spinocerebellar ataxia type 1 (SCA1), a gain of function of polyQ-expanded ataxin-1 (ATXN1) contributes to cerebellar pathology. The extent to which cerebellar toxicity depends on its cognate partner capicua (CIC), versus other interactors, remains unclear. It is also not established whether loss of the ATXN1-CIC complex in the cerebellum contributes to disease pathogenesis. In this study, we exclusively disrupt the ATXN1-CIC interaction in vivo and show that it is at the crux of cerebellar toxicity in SCA1. Importantly, loss of CIC in the cerebellum does not cause ataxia or Purkinje cell degeneration. Expression profiling of these gain- and loss-of-function models, coupled with data from iPSC-derived neurons from SCA1 patients, supports a mechanism in which gain of function of the ATXN1-CIC complex is the major driver of toxicity.

Loss of Capicua alters early T cell development and predisposes mice to T cell lymphoblastic leukemia/lymphoma

Capicua (CIC) regulates a transcriptional network downstream of the RAS/MAPK signaling cascade. In Drosophila, CIC is important for many developmental processes, including embryonic patterning and specification of wing veins. In humans, CIC has been implicated in neurological diseases, including spinocerebellar ataxia type 1 (SCA1) and a neurodevelopmental syndrome. Additionally, we and others have reported mutations in CIC in several cancers. However, whether CIC is a tumor suppressor remains to be formally tested. In this study, we found that deletion of Cic in adult mice causes T cell acute lymphoblastic leukemia/lymphoma (T-ALL). Using hematopoietic-specific deletion and bone marrow transplantation studies, we show that loss of Cic from hematopoietic cells is sufficient to drive T-ALL. Cic-null tumors show up-regulation of the KRAS pathway as well as activation of the NOTCH1 and MYC transcriptional programs. In sum, we demonstrate that loss of CIC causes T-ALL, establishing it as a tumor suppressor for lymphoid malignancies. Moreover, we show that mouse models lacking CIC in the hematopoietic system are robust models for studying the role of RAS signaling as well as NOTCH1 and MYC transcriptional programs in T-ALL.

A double-edged sword: The world according to Capicua in cancer

CIC/Capicua is an HMG‐box transcription factor that is well conserved during evolution. CIC recognizes the T(G/C)AATG(A/G)A sequence and represses its target genes, such as PEA3 family genes. The receptor tyrosine kinase/RAS/MAPK signals downregulate CIC and relieves CIC's target genes from the transrepressional activity; CIC thus acts as an important downstream molecule of the pathway and as a tumor suppressor. CIC loss‐of‐function mutations are frequently observed in several human neoplasms such as oligodendroglioma, and lung and gastric carcinoma. CIC is also involved in chromosomal translocation‐associated gene fusions in highly aggressive small round cell sarcoma that is biologically and clinically distinct from Ewing sarcoma. In these mutations, PEA3 family genes and other important target genes are upregulated, inducing malignant phenotypes. Downregulation of CIC abrogates the effect of MAPK inhibitors, suggesting its potential role as an important modifier of molecular target therapies for cancer. These data reveal the importance of CIC as a key molecule in signal transduction, carcinogenesis, and developing novel therapies.