Nuclear Wiskott-Aldrich syndrome protein co-regulates T cell factor 1-mediated transcription in T cells

Accumulation of circulating myeloid-derived suppressor cell subsets: predicting poor clinical efficacy and prognosis through T cell suppression in non-Hodgkin's lymphoma

Myeloid-derived suppressor cells (MDSCs) are implicated in the regulation of immune responses closely associated with poor clinical outcomes in cancer. However, the MDSC subtypes in non-Hodgkin's lymphoma (NHL) have not been systematically investigated. So, we investigated the percentage of MDSC subsets in 78 newly diagnosed NHL patients by flow cytometry. The results showed that all MDSC subsets increased in NHL patients compared with healthy donors. Notably, MDSCs, monocytic MDSCs, and CD14 + CD66b + MDSCs significantly increased in NHL patients compared with those with lymphadenitis donors. polymorphonuclear MDSCs (PMN-MDSCs), early-stage MDSCs (e-MDSCs), and the International Prognostic Index were independent risk factors for poor clinical efficacy and were involved in constructing the nomogram for predicting clinical efficacy. Progression-free survival (PFS) was significantly shorter in patients with high level of MDSC subsets, and PMN-MDSCs emerged as an independent prognostic factor for PFS. PMN-MDSCs, e-MDSCs, and the International Prognostic Index were involved in constructing the nomogram for predicting PFS. Patients with a higher percentage of MDSCs, PMN-MDSCs, e-MDSCs, and CD14 + CD66b + MDSCs experienced a shorter overall survival compared with those with lower percentages. In addition, research on mechanisms found that T cell function was suppressed and mediated by the expansion of MDSCs via involving arginase-1 and interleukin-10 in vitro and in vivo. In conclusion, our study demonstrates that the increased circulating MDSC subsets predict poor clinical efficacy and prognosis in NHL, potentially involving T cell suppression through MDSC subset expansion. These findings indicate the potential of MDSC subsets as comprehensive diagnostic, prognostic biomarkers, and therapeutic targets for NHL.

Exposure of volunteers to microgravity by dry immersion bed over 21 days results in gene expression changes and adaptation of T cells

The next steps of deep space exploration are manned missions to Moon and Mars. For safe space missions for crew members, it is important to understand the impact of space flight on the immune system. We studied the effects of 21 days dry immersion (DI) exposure on the transcriptomes of T cells isolated from blood samples of eight healthy volunteers. Samples were collected 7 days before DI, at day 7, 14, and 21 during DI, and 7 days after DI. RNA sequencing of CD3+ T cells revealed transcriptional alterations across all time points, with most changes occurring 14 days after DI exposure. At day 21, T cells showed evidence of adaptation with a transcriptional profile resembling that of 7 days before DI. At 7 days after DI, T cells again changed their transcriptional profile. These data suggest that T cells adapt by rewiring their transcriptomes in response to simulated weightlessness and that remodeling cues persist when reexposed to normal gravity.

Understanding immunoactinopathies: A decade of research on WAS gene defects

Immunoactinopathies caused by mutations in actin-related proteins are a growing group of inborn errors of immunity (IEI). Immunoactinopathies are caused by a dysregulated actin cytoskeleton and affect hematopoietic cells especially because of their unique capacity to survey the body for invading pathogens and altered self, such as cancer cells. These cell motility and cell-to-cell interaction properties depend on the dynamic nature of the actin cytoskeleton. Wiskott-Aldrich syndrome (WAS) is the archetypical immunoactinopathy and the first described. WAS is caused by loss-of-function and gain-of-function mutations in the actin regulator WASp, uniquely expressed in hematopoietic cells. Mutations in WAS cause a profound disturbance of actin cytoskeleton regulation of hematopoietic cells. Studies during the last 10 years have shed light on the specific effects on different hematopoietic cells, revealing that they are not affected equally by mutations in the WAS gene. Moreover, the mechanistic understanding of how WASp controls nuclear and cytoplasmatic activities may help to find therapeutic alternatives according to the site of the mutation and clinical phenotypes. In this review, we summarize recent findings that have added to the complexity and increased our understanding of WAS-related diseases and immunoactinopathies.

Transcriptional Regulation of Early T-Lymphocyte Development in Thymus

T-lymphocytes play crucial roles for maintaining immune homeostasis by fighting against various pathogenic microorganisms and establishing self-antigen tolerance. They will go through several stages and checkpoints in the thymus from progenitors to mature T cells, from CD4^-CD8^- double negative (DN) cells to CD4⁺CD8⁺ double positive (DP) cells, finally become CD4⁺ or CD8⁺ single positive (SP) cells. The mature SP cells then emigrate out of the thymus and further differentiate into distinct subsets under different environment signals to perform specific functions. Each step is regulated by various transcriptional regulators downstream of T cell receptors (TCRs) that have been extensively studied both in vivo and vitro via multiple mouse models and advanced techniques, such as single cell RNA sequencing (scRNA-seq) and Chromatin Immunoprecipitation sequencing (ChIP-seq). This review will summarize the transcriptional regulators participating in the early stage of T cell development reported in the past decade, trying to figure out cascade networks in each process and provide possible research directions in the future.

Journey to the Center of the Cell: Cytoplasmic and Nuclear Actin in Immune Cell Functions

Actin cytoskeletal dynamics drive cellular shape changes, linking numerous cell functions to physiological and pathological cues. Mutations in actin regulators that are differentially expressed or enriched in immune cells cause severe human diseases known as primary immunodeficiencies underscoring the importance of efficienct actin remodeling in immune cell homeostasis. Here we discuss recent findings on how immune cells sense the mechanical properties of their environement. Moreover, while the organization and biochemical regulation of cytoplasmic actin have been extensively studied, nuclear actin reorganization is a rapidly emerging field that has only begun to be explored in immune cells. Based on the critical and multifaceted contributions of cytoplasmic actin in immune cell functionality, nuclear actin regulation is anticipated to have a large impact on our understanding of immune cell development and functionality.

Higher Incidence of B Cell Malignancies in Primary Immunodeficiencies: A Combination of Intrinsic Genomic Instability and Exocytosis Defects at the Immunological Synapse

Congenital defects of the immune system called primary immunodeficiency disorders (PID) describe a group of diseases characterized by a decrease, an absence, or a malfunction of at least one part of the immune system. As a result, PID patients are more prone to develop life-threatening complications, including cancer. PID currently include over 400 different disorders, however, the variety of PID-related cancers is narrow. We discuss here reasons for this clinical phenotype. Namely, PID can lead to cell intrinsic failure to control cell transformation, failure to activate tumor surveillance by cytotoxic cells or both. As the most frequent tumors seen among PID patients stem from faulty lymphocyte development leading to leukemia and lymphoma, we focus on the extensive genomic alterations needed to create the vast diversity of B and T lymphocytes with potential to recognize any pathogen and why defects in these processes lead to malignancies in the immunodeficient environment of PID patients. In the second part of the review, we discuss PID affecting tumor surveillance and especially membrane trafficking defects caused by altered exocytosis and regulation of the actin cytoskeleton. As an impairment of these membrane trafficking pathways often results in dysfunctional effector immune cells, tumor cell immune evasion is elevated in PID. By considering new anti-cancer treatment concepts, such as transfer of genetically engineered immune cells, restoration of anti-tumor immunity in PID patients could be an approach to complement standard therapies.

Involvement of Actin and Actin-Binding Proteins in Carcinogenesis

The actin cytoskeleton plays a crucial role in many cellular processes while its reorganization is important in maintaining cell homeostasis. However, in the case of cancer cells, actin and ABPs (actin-binding proteins) are involved in all stages of carcinogenesis. Literature has reported that ABPs such as SATB1 (special AT-rich binding protein 1), WASP (Wiskott-Aldrich syndrome protein), nesprin, and villin take part in the initial step of carcinogenesis by regulating oncogene expression. Additionally, changes in actin localization promote cell proliferation by inhibiting apoptosis (SATB1). In turn, migration and invasion of cancer cells are based on the formation of actin-rich protrusions (Arp2/3 complex, filamin A, fascin, α-actinin, and cofilin). Importantly, more and more scientists suggest that microfilaments together with the associated proteins mediate tumor vascularization. Hence, the presented article aims to summarize literature reports in the context of the potential role of actin and ABPs in all steps of carcinogenesis.

Faecal microbial dysbiosis in children with Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency disease caused by a mutation in the WAS gene that encodes the WAS protein (WASp); up to 5-10% of these patients develop inflammatory bowel disease (IBD). The mechanisms by which WASp deficiency causes IBD are unclear. Intestinal microbial dysbiosis and imbalances in host immune responses play important roles in the pathogenesis of polygenetic IBD; however, few studies have conducted detailed examination of the microbial alterations and their relationship with IBD in WAS. Here, we collected faecal samples from 19 children (all less than 2 years old) with WAS and samples from WASp-KO mice with IBD and subjected them to 16S ribosomal RNA sequencing. We found that microbial community richness and structure in WAS children were different from those in controls; WAS children revealed reduced microbial community richness and diversity. Relative abundance of Bacteroidetes and Verrucomicrobiain in WAS children was significantly lower, while that of Proteobacteria was markedly higher. WASp-KO mice revealed a significantly decreased abundance of Firmicutes. Faecal microbial dysbiosis caused by WASp deficiency is similar to that observed for polygenetic IBD, suggesting that WASp may play crucial function in microbial homoeostasis and that microbial dysbiosis may contribute to IBD in WAS. These microbial alterations may be useful targets for monitoring and therapeutically managing intestinal inflammation in WAS.

Dedicator of cytokinesis protein 2 couples with lymphoid enhancer-binding factor 1 to regulate expression of CD21 and B-cell differentiation

BACKGROUND

B-cell receptor (BCR) signaling, combined with CD19 and CD21 signals, imparts specific control of B-cell responses. Dedicator of cytokinesis protein 2 (DOCK2) is critical for the migration and motility of lymphocytes. Although absence of DOCK2 leads to lymphopenia, little is known about the signaling mechanisms and physiologic functions of DOCK2 in B cells.

OBJECTIVE

We sought to determine the underlying molecular mechanism of how DOCK2 regulates BCR signaling and peripheral B-cell differentiation.

METHODS

In this study we used genetic models for DOCK2, Wiskott-Aldrich syndrome protein (WASP), and lymphoid enhancer-binding factor 1 deficiency to study their interplay in BCR signaling and B-cell differentiation.

RESULTS

We found that the absence of DOCK2 led to downregulation of proximal and distal BCR signaling molecules, including CD19, but upregulation of SH2-containing inositol 5 phosphatase 1, a negative signaling molecule. Interestingly, DOCK2 deficiency reduced CD19 and CD21 expression at the mRNA and/or protein levels and was associated with reduced numbers of marginal zone B cells. Additionally, loss of DOCK2 reduced activation of WASP and accelerated degradation of WASP, resulting into reduced actin accumulation and early activation of B cells. Mechanistically, the absence of DOCK2 upregulates the expression of lymphoid enhancer-binding factor 1. These differences were associated with altered humoral responses in the absence of DOCK2.

CONCLUSIONS

Overall, our study has provided a novel underlying molecular mechanism of how DOCK2 deficiency regulates surface expression of CD21, which leads to downregulation of CD19-mediated BCR signaling and marginal zone B-cell differentiation.

The role of WASp in T cells and B cells

Wiskott-Aldrich syndrome (WAS) is a form of primary immunodeficiency (PIDs) resulting from mutations of the gene that encodes Wiskott-Aldrich syndrome protein (WASp). WASp is the first identified and most widely studied protein belonging to the actin nucleation-promoting factor family and plays significant role in integrating and transforming signals from critical receptors on the cell surface to actin remodeling. WASp functions in immune defense and homeostasis through the regulation of actin cytoskeleton-dependent cellular processes as well as processes uncoupled with actin polymerization like nuclear transcription programs. In this article, we review the mechanisms of WASp activation through an understanding of its structure. We further discuss the role of WASp in adaptive immunity, paying special attention to some recent findings on the crucial role of WASp in the formation of immunological synapse, the regulation of T follicular helper (Tfh) cells and in the prevention of autoimmunity.

Down-regulated lncRNA MEG3 promotes osteogenic differentiation of human dental follicle stem cells by epigenetically regulating Wnt pathway

Our previous long noncoding RNA (lncRNA) microarray results showed that lncRNA MEG3 (maternally expressed 3) was significantly downregulated in human dental follicle cells than human periodontal ligament cells. Latest studies show that MEG3 contributes to polycomb repressive complex 2 (PRC2) recruitment to silence gene expression. The enhancer of zeste homolog 2 (EZH2), a crucial catalytic subunit of PRC2, mediates gene silencing and participates in cell lineage determination via methyltransferase activity. In this study, we found that the expression of EZH2 and H3K27me3 (trimethylation on lysine 27 in histone H3) decreased during osteogenesis of human dental follicle stem cells (hDFSCs). Knockdown studies of MEG3 and EZH2 by siRNA showed that MEG3/EZH2 negatively regulated osteogenesis of hDFSCs. We investigated the role of Wnt signaling pathway during the osteogenesis of hDFSCs and its relationship with EZH2. Besides, we studied the key genes of the canonical/noncanonical Wnt signaling pathway which might be related to EZH2. ChIP (chromatin immunoprecipitation) analysis showed that these effects were due to the EZH2 regulation of H3K27me3 level on the Wnt genes promotors. We first demonstrated that the decrease of MEG3 or EZH2 activated the Wnt/β-catenin signaling pathway via epigenetically regulating the H3K27me3 level on the Wnt genes promotors. Our research offers a new target for periodontal tissue engineering and osteogenic tissue regeneration.

R-loops cause genomic instability in T helper lymphocytes from patients with Wiskott-Aldrich syndrome

BACKGROUND

Wiskott-Aldrich syndrome (WAS), X-linked thrombocytopenia (XLT), and X-linked neutropenia, which are caused by WAS mutations affecting Wiskott-Aldrich syndrome protein (WASp) expression or activity, manifest in immunodeficiency, autoimmunity, genomic instability, and lymphoid and other cancers. WASp supports filamentous actin formation in the cytoplasm and gene transcription in the nucleus. Although the genetic basis for XLT/WAS has been clarified, the relationships between mutant forms of WASp and the diverse features of these disorders remain ill-defined.

OBJECTIVE

We sought to define how dysfunctional gene transcription is causally linked to the degree of T_H cell deficiency and genomic instability in the XLT/WAS clinical spectrum.

METHODS

In human T_H1- or T_H2-skewing cell culture systems, cotranscriptional R-loops (RNA/DNA duplex and displaced single-stranded DNA) and DNA double-strand breaks (DSBs) were monitored in multiple samples from patients with XLT and WAS and in normal T cells depleted of WASp.

RESULTS

WASp deficiency provokes increased R-loops and R-loop-mediated DSBs in T_H1 cells relative to T_H2 cells. Mechanistically, chromatin occupancy of serine 2-unphosphorylated RNA polymerase II is increased, and that of topoisomerase 1, an R-loop preventing factor, is decreased at R-loop-enriched regions of IFNG and TBX21 (T_H1 genes) in T_H1 cells. These aberrations accompany increased unspliced (intron-retained) and decreased spliced mRNA of IFNG and TBX21 but not IL13 (T_H2 gene). Significantly, increased cellular load of R-loops and DSBs, which are normalized on RNaseH1-mediated suppression of ectopic R-loops, inversely correlates with disease severity scores.

CONCLUSION

Transcriptional R-loop imbalance is a novel molecular defect causative in T_H1 immunodeficiency and genomic instability in patients with WAS. The study proposes that cellular R-loop load could be used as a potential biomarker for monitoring symptom severity and prognostic outcome in the XLT-WAS clinical spectrum and could be targeted therapeutically.