Atypical Phenotype of Predominant Autoimmune Cytopenia and Impaired Perforin Expression in XMEN Syndrome

MAGT1 messenger RNA-corrected autologous T and natural killer cells for potential cell therapy in X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection and neoplasia disease

Highly Efficient & Specific Repair of MAGT1 Mutation in Xmen Patient T Cells and Hematopoietic Stem Cells

To describe the role of the magnesium transporter 1 (MAGT1) in the pathogenesis of 'X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection, and neoplasia' (XMEN) disease and its clinical implications. The magnesium transporter protein MAGT1 participates in the intracellular magnesium ion (Mg) homeostasis and facilitates a transient Mg influx induced by the activation of the T-cell receptor. Loss-of-function mutations in MAGT1 cause an immunodeficiency named 'XMEN syndrome', characterized by CD4 lymphopenia, chronic EBV infection, and EBV-related lymphoproliferative disorders. Patients with XMEN disease have impaired T-cell activation and decreased cytolytic function of natural killer (NK) and CD8 T cells because of decreased expression of the NK stimulatory receptor 'natural-killer group 2, member D' (NKG2D). Patients may have defective specific antibody responses secondary to T cell dysfunction, but B cells have not been shown to be directly affected by mutations in MAGT1. XMEN disease has revealed a novel role for free intracellular magnesium in the immune system. Further understanding of the MAGT1 signaling pathway may lead to new diagnostic and therapeutic approaches.

An Unexpected Diagnosis of MAGT1 Deficiency in a Patient with CVID-like Features, Molluscum Contagiosum and Atopy

MAGT1 (magnesium transporter 1) is a subunit of the oligosaccharide protein complex with thiol-disulfide oxidoreductase activity, supporting the process of N-glycosylation. MAGT1 deficiency was detected in human patients with X-linked immunodeficiency with magnesium defect syndrome and congenital disorders of glycosylation, resulting in decreased cation responses in lymphocytes, thereby inhibiting the immune response against viral infections. Curative hematopoietic stem cell transplantation of patients with X-linked immunodeficiency with magnesium defect causes fatal bleeding and thrombotic complications. We studied the role of MAGT1 deficiency in platelet function in relation to arterial thrombosis and hemostasis using several in vitro experimental settings and in vivo models of arterial thrombosis and transient middle cerebral artery occlusion model of ischemic stroke. MAGT1-deficient mice (Magt1-/y) displayed accelerated occlusive arterial thrombus formation in vivo, a shortened bleeding time, and profound brain damage upon focal cerebral ischemia. These defects resulted in increased calcium influx and enhanced second wave mediator release, which further reinforced platelet reactivity and aggregation responses. Supplementation of MgCl2 or pharmacological blockade of TRPC6 (transient receptor potential cation channel, subfamily C, member 6) channels, but not inhibition of store-operated calcium entry, normalized the aggregation responses of Magt1-/y platelets to the control level. GP (glycoprotein) VI activation of Magt1-/y platelets resulted in hyperphosphorylation of Syk (spleen tyrosine kinase), LAT (linker for activation of T cells), and PLC (phospholipase C) γ2, whereas the inhibitory loop regulated by PKC (protein kinase C) was impaired. A hyperaggregation response to the GP VI agonist was confirmed in human platelets isolated from a MAGT1-deficient (X-linked immunodeficiency with magnesium defect) patient. Haploinsufficiency of TRPC6 in Magt1-/y mice could normalize GP VI signaling, platelet aggregation, and thrombus formation in vivo. These results suggest that MAGT1 and TRPC6 are functionally linked. Therefore, deficiency or impaired functionality of MAGT1 could be a potential risk factor for arterial thrombosis and stroke.

“X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection, and neoplasia” (XMEN) disease is an inborn error of glycosylation and immunity caused by loss of function mutations in the magnesium transporter 1 (MAGT1) gene. It is a multisystem disease that strongly affects certain immune cells. MAGT1 is now confirmed as a non-catalytic subunit of the oligosaccharyltransferase complex and facilitates Asparagine (N)-linked glycosylation of specific substrates, making XMEN a congenital disorder of glycosylation manifesting as a combined immune deficiency. The clinical disease has variable expressivity and impaired glycosylation of key MAGT1-dependent glycoproteins in addition to Mg2+ abnormalities can explain some of the immune manifestations. NKG2D, an activating receptor critical for cytotoxic function against EBV, is poorly glycosylated and invariably decreased on CD8+ T cells and natural killer (NK) cells from XMEN patients. It is the best biomarker of the disease. The characterization of EBV-naïve XMEN patients has clarified features of the genetic disease that were previously attributed to EBV infection. Extra-immune manifestations, including hepatic and neurological abnormalities have recently been reported. EBV-associated lymphomas remain the main cause of severe morbidity. Unfortunately, treatment options to address the underlying mechanism of disease remain limited and Mg2+ supplementation has not proven successful. Here, we review the expanding clinical phenotype and recent advances in glycobiology that have increased our understanding of XMEN disease. We also propose updating XMEN to “X-linked MAGT1 deficiency with increased susceptibility to EBV-infection and N-linked glycosylation defect” in light of these novel findings.

Magnesium transporter 1 (MAGT1) critically mediates magnesium homeostasis in eukaryotes and is highly-conserved across different evolutionary branches. In humans, loss-of-function mutations in the MAGT1 gene cause X-linked magnesium deficiency with Epstein-Barr virus (EBV) infection and neoplasia (XMEN), a disease that has a broad range of clinical and immunological consequences. We have previously shown that EBV susceptibility in XMEN is associated with defective expression of the antiviral natural-killer group 2 member D (NKG2D) protein and abnormal Mg2+ transport. New evidence suggests that MAGT1 is the human homolog of the yeast OST3/OST6 proteins that form an integral part of the N-linked glycosylation complex, although the exact contributions of these perturbations in the glycosylation pathway to disease pathogenesis are still unknown. Using MS-based glycoproteomics, along with CRISPR/Cas9-KO cell lines, natural killer cell-killing assays, and RNA-Seq experiments, we now demonstrate that humans lacking functional MAGT1 have a selective deficiency in both immune and nonimmune glycoproteins, and we identified several critical glycosylation defects in important immune-response proteins and in the expression of genes involved in immunity, particularly CD28. We show that MAGT1 function is partly interchangeable with that of the paralog protein tumor-suppressor candidate 3 (TUSC3) but that each protein has a different tissue distribution in humans. We observed that MAGT1-dependent glycosylation is sensitive to Mg2+ levels and that reduced Mg2+ impairs immune-cell function via the loss of specific glycoproteins. Our findings reveal that defects in protein glycosylation and gene expression underlie immune defects in an inherited disease due to MAGT1 deficiency.

Loss-of-function mutations in magnesium transporter 1 (MAGT1) gene cause X-linked magnesium deficiency with Epstein-Barr virus (EBV) infection and neoplasm (X-MEN), a disease with quite diverse clinical and immunological consequences. The phenotypic characteristics of the initially described patients included CD4+ T cell lymphopenia, immune deficiency, EBV viremia, and EBV-related lymphoproliferative disease. To date, a total of 25 patients have been reported. The spectrum of the MAGT1 defect ranges from other viral infections (HSV, VZV, CMV, MCV) and sinopulmonary bacterial infections, autoimmune diseases, non-EBV driven lymphoproliferative disease, Castleman disease, HHV8+ Kaposi's sarcoma, vasculitis (Kawasaki) to glycosylation defects in new patients. Here, we report 2 patients from two different families with novel MAGT1 mutations and different clinical features. The first patient presented with B cell lymphoma and low IgM level without recurrent infections. The second patient presented with recurrent upper respiratory tract infections, Kawasaki-like disease, hypogammaglobulinemia, and T cell lymphopenia. X-MEN disease is the first phenotype identified due to MAGT1 mutation. The identification of new mutations and atypical presentations will clarify whether there is a relationship between the genotype and the phenotype and the characteristics of the disease.

Disturbances in magnesium homeostasis, often linked to altered expression and/or function of magnesium channels, have been implicated in a plethora of diseases. This review focuses on magnesium transporter 1 (MAGT1), as recently described changes in this gene have further extended our understanding of the role of magnesium in human health and disease. The identification of genetic changes and their functional consequences in patients with immunodeficiency revealed that magnesium and MAGT1 are key molecular players for T cell-mediated immune responses. This led to the description of XMEN (X-linked immunodeficiency with magnesium defect, Epstein Barr Virus infection, and neoplasia) syndrome, for which Mg2+ supplementation has been shown to be beneficial. Similarly, the identification of a copy-number variation (CNV) leading to dysfunctional MAGT1 in a family with atypical ATRX syndrome and skin abnormalities, suggested that the MAGT1 defect could be responsible for the cutaneous problems. On the other hand, recent genetic investigations question the previously proposed role for MAGT1 in intellectual disability. Understanding the molecular basis of the involvement of magnesium and its channels in human pathogenesis will improve opportunities for Mg2+ therapies in the clinic.

BackgroundX-linked immunodeficiency with magnesium defect and Epstein-Barr virus infection and neoplasia (XMEN) disease is an X-linked genetic disorder of immune system caused by loss-of-function mutation in gene encoding Magnesium transporter 1 (MAGT1). Individuals with XMEN disease are prone to developing Epstein Barr Virus (EBV)-associated lymphomas. Herein, we report the first known case of an EBV+ EMZL associated with XMEN disease.Case presentationThe patient was an 8-year-old Chinese boy who suffered from recurrent infections from birth. Six months before, the patient presented with a painless mass on his upper lip and excisional biopsy revealed an EBV-positive extra-nodal marginal zone lymphoma (EBV+ EMZL). Furthermore, molecular investigations with next-generation sequencing identified a novel germline mutation in MAGT1 (c.828_829insAT) in the patient. The c.828_829insAT variant was predicted to cause premature truncation of MAGT1 (p.A277M.fs*11) and consequently was defined as likely pathogenic. The mutation was inherited from his asymptomatic heterozygous carrier mother. Hence the patient was diagnosed with an XMEN disease both clinically and genetically.ConclusionOur results expand the genetic spectrum of XMEN disease and also the clinical spectrum of EBV+ EMZL. We highlight the importance of the genetic etiology underlying EBV+ lymphoma in the pediatric population.

Magnesium transporter 1 (MAGT1) is a key protein that regulates the level of free Mg2+ in cells. Previous studies found that the downregulation of MAGT1 expression in CD8+T cells of HBV patients was correlated with the decrease of intracellular magnesium. However, the expression of MAGT1 mRNA in the CD8+T cells from HBV patients was not significantly altered, indicating that the change in MAGT1 expression was accomplished through posttranscriptional regulation. Through bioinformatics and qRT-PCR detection, miR-199a-5p was found to have a target gene relationship with MAGT1. The expression levels of miR-199a-5p and MAGT1 in HBV infection were evaluated. Lentivirus assays were used to analyze the effects of miR-199a-5p upregulation and downregulation on the MAGT1 expression level and the immune system. Results showed no significant change in the expression of MAGT1 mRNA in HBV-infected cell lines, but the expression of MAGT1 was downregulated. Additionally, the expression level of miR-199a-5p was significantly increased. To this end, we predicted a target relationship between miR-199a-5p and MAGT1 by using TargetScan and verified this relationship through a luciferase activity reporter gene assay. As a result, MAGT1 was found to be the direct target of miR-199a-5p. The targeted inhibition of MAGT1 induced by miR-199a-5p overexpression led to the immune function depletion of CD8+T cells in HBV patients. Downregulating the expression level of miR-199a-5p could effectively improve the functional depletion of CD8+T cells. These findings indicate that miR-199a-5p and MAGT1 could potentially be used as biomarkers for the diagnosis and treatment of chronic HBV infection.

X-linked MAGT1 deficiency with increased susceptibility to Epstein-Barr virus (EBV) infection and N-linked glycosylation defect (XMEN) disease is an inborn error of immunity caused by loss-of-function mutations in the magnesium transporter 1 (MAGT1) gene. The original studies of XMEN patients focused on impaired magnesium regulation, leading to decreased EBV-cytotoxicity and the loss of surface expression of the activating receptor "natural killer group 2D" (NKG2D) on CD8+ T cells and NK cells. In vitro studies showed that supraphysiological supplementation of magnesium rescued these defects. Observational studies in 2 patients suggested oral magnesium supplementation could decrease EBV viremia. Hence, we performed a randomized, double-blind, placebo-controlled, crossover study in 2 parts. In part 1, patients received either oral magnesium L-threonate (MLT) or placebo for 12weeks followed by 12weeks of the other treatment. Part 2 began with 3days of high-dose intravenous (IV) magnesium sulfate (MgSO4) followed by open-label MLT for 24weeks. One EBV-infected and 3 EBV-naïve patients completed part 1. One EBV-naïve patient was removed from part 2 of the study due to asymptomatic elevation of liver enzymes during IV MgSO4. No change in EBV or NKG2D status was observed. In vitro magnesium supplementation experiments in cells from 14 XMEN patients failed to significantly rescue NKG2D expression and the clinical trial was stopped. Although small, this study indicates magnesium supplementation is unlikely to be an effective therapeutic option in XMEN disease.

BackgroundSelective anti-polysaccharide antibody deficiency (SPAD) with CD5 B-cell predominance and autoimmune phenomena was identified in a male cohort first reported by Antall et al in 1999. The phenotypically likewise and genotypically identical X-linked immunodeficiency with magnesium defect, Epstein–Barr Virus infection, and neoplasia (XMEN) disease was defined as a novel primary immunodeficiency (PID) in 2011. Recent studies of the magnesium transporter 1 (MAGT1) gene mutation reveal glycosylation defects contributing to more phenotypic variance than the “XMEN” title pathologies. The updated title, “X-linked MAGT1 deficiency with increased susceptibility to EBV-infection and N-linked glycosylation defect,” was proposed in 2020.ObjectivesTo reflect the patient population more accurately, a prospective classification update may consider MAGT1 glycobiological errors contributing to phenotypic variance but also pre-genetic testing era reports with CD5 B-cell predominance.MethodsPatient 1 from Antall et al presented at 28 years of age for further immunological evaluation of his CD5/CD19 B-cell predominance diagnosed at 5 years old.DesignImmune re-evaluation done through flow cytometry and next-generation sequencing.ResultsFlow cytometry B-cell phenotyping revealed persistent CD5+CD19+ (93%). Flow cytometric histogram quantified reduced activator CD16+CD56+ natural killer and CD8+ T-cell receptor, Group 2, Member D (NKG2D) glycoprotein expression. A c.923-1_934 deletion loss of function mutation was identified in the MAGT1 gene.ConclusionWe suggest the novel PID XMEN, based on its CD5 B-cell predominance, had been discovered and reported over a decade earlier as CD5+ PID based on the MAGT1 mutation found in the same. We encourage consideration of combining these labels and recent findings to offer the most accurate classification of this disease.

BackgroundNovel messenger RNA vaccines against severe acute respiratory syndrome coronavirus (SARS-CoV-2) have been vital in resolving the coronavirus disease-2019 (COVID-19) pandemic. Detection of neutralizing antibodies (NAbs) against the SARS-CoV-2 spike protein (S) confirms immunogenicity with high sensitivity and specificity. Few recent studies with primary and secondary immunodeficient cohorts present adequate or reduced antibody response. We describe the first reported successful response to anti-SARS-CoV-2 S antibody post-vaccination in magnesium transporter 1 (MAGT1) gene deficiency, more commonly recognized as x-linked immunodeficiency with magnesium defect, Epstein-Barr Virus infection, and neoplasia (XMEN).Case PresentationWe present a 30-year-old male with selective anti-polysaccharide antibody deficiency, peripheral blood CD5 + /CD19 + B-cell predominance (97%), MAGT1 mutation, and reduced CD16 + CD56 + natural killer- and/or CD8 + T-cell receptor, Group 2, Member D expression. His initial immunological evaluation revealed all seronegative post-vaccination antibody titers but clinically adequate response to protein antigens tetanus and diphtheria anti-toxoids.COVID-19 vaccination and associated serology antibody testing was recommended at this office visit. Anti-SARS-CoV-2 immunoglobulin (Ig)M and IgG antibodies before and after the first BNT162b2 mRNA COVID-19 vaccine doses, as well as nucleocapsid antibody, were negative. S protein total antibody was reactive after the second dose.DiscussionRobust immunological sequelae post-COVID-19 vaccination in the general population are well-documented in the recent literature. Few studies have evaluated COVID-19 vaccination antibody response in immunodeficient patients. The majority positive anti-S antibody detection in most primary immunodeficient (PID) patients among the few studies in the literature, such as the present case, support the safety and efficacy of mRNA COVID-19 vaccination in immunodeficient patients, although larger scale studies are needed. ConclusionWe demonstrate successful vaccination in the PID MAGT1 deficiency in this first reported case of reactive anti-S antibody post-COVID-19 vaccination.

As a highly malignant gastrointestinal tumor, pancreatic carcinoma (PC) has poor prognosis due to its low early diagnosis rate, advanced tumor resection and chemotherapy resistance. Magnesium transporter 1 (MAGT1) is a magnesium ion transporter located on the cell membrane, which shows promotive effects on biological behaviors of multiple tumor cells. The aim of the present study was to investigate the role of MAGT1 in the progression of PC and its potential molecular mechanism. Based on the Gene Expression Profiling Interactive Analysis website, MAGT1 was highly expressed in tissues from patients with PC and was associated with poor prognosis. In functional experiments, MAGT1 was highly expressed in PC cell lines. The Cell Counting Kit-8, gap closure and Transwell assays, and western blot analysis, were used to investigate the effects of MAGT1 overexpression or knockdown on the biological behaviors of PC cells. It was found that MAGT1 promoted the proliferation, migration and invasion of PC cells in vitro. According to the Encyclopedia of RNA Interactomes website, transcription factor 12 (TCF12) mRNA expression level was positively correlated with MAGT1 expression level in the tissues from patients with PC. Positive targeting regulation of MAGT1 by TCF12 was also confirmed using a dual-luciferase gene reporter assay and chromatin immunoprecipitation. In addition, knockdown of TCF12 expression inhibited the proliferation and migration of PC cells, but overexpression of MAGT1 expression partly reversed this. These results suggested that TCF12 could promote the proliferation, migration and invasion of PC cells by activating MAGT1 expression, which was associated with poor prognosis. These findings suggest that MAGT1 could be a promising biomarker for the occurrence, progression and prognosis of PC.