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At least 73 records · Page 4Linked to original sources

DDX3X overexpression in mice can cause rapid tissue-specific toxicity and mortality.

DEAD-Box Helicase 3 X-Linked (DDX3X) is a ubiquitously expressed RNA helicase with diverse cellular roles implicated in a neurodevelopmental disorder called DDX3X syndrome. Although DDX3X is a leading genetic cause of intellectual disability in females, there is no treatment. While gene supplementation is a plausible therapeutic strategy, previous studies suggest DDX3X is carefully regulated and dose sensitive. To understand the consequences of overexpressing DDX3X with unregulated adeno-associated virus-mediated gene supplementation, we generated a vector driving strong ubiquitous DDX3X expression and administered it through a direct cerebrospinal fluid injection in newborn mice. Mice injected with a high dose died within 1 week from myocardial degeneration. Increased expression of stress response markers together with elevated apoptotic signaling in the heart suggested activation of stress-induced apoptotic pathways. Incidental findings included excess lipid accumulation, most prominent in the liver, and other liver injury. The innate immune system was also highly activated in the heart and liver. Interestingly, the brain was overall unaffected. The results suggest that DDX3X overexpression can cause rapid transgene-driven, tissue-specific toxicity, underscoring the need for tight DDX3X gene dosage control. These findings illustrate the possibility for improper transgene expression to drive severe toxicity including death within days following administration.

Animals↗

Pathogenesis and phenotypes of an X-linked recessive lymphoproliferative syndrome.

A new X-linked recessive lymphoproliferative syndrome has variable phenotypes: fatal infectious mononucleosis (I.M.), agammaglobulinaemia after I.M., American Burkitt's lymphoma, histiocytic lymphoma, immunoblastic sarcoma of B cells, or plasmacytoma. An immunodeficiency to rubeola and the Epstein-Barr virus probably ensues from the mutant gene. The phenotypes (spectrum of B-cell disorders) have a common inheritance and the aetiology is similar.

Adolescent↗

Generation of anti-type III pneumococcal polysaccharide hybridomas from mice with an X-linked B-lymphocyte defect.

(CBA/N X BALB/c male)F1 mice bear on X-linked defect making them totally unresponsive to T-independent (TI), TI-2 antigens such as type III pneumococcal polysaccharide (SSS-III). We found that somatic cell hybrids between CB nonresponder spleen cells and NS1 plasmacytoma cells secreted antibody specific for SSS-III. The solid-phase binding of such antibody was completely inhibited by the addition of free antigen (SSS-III) and the amount of antibody detected in culture fluids ranged from 10 ng/ml to 10 micrograms/ml. Eight hybridoma clones were identified; all make antibody of the IgM class. These results indicate that the X-linked defect does not result in a deletion of a B-cell subset which responds to TI-2 antigens.

Animals↗

Estimation of carrier frequencies of autosomal and X-linked recessive genetic conditions based on gnomAD v4.0 data in different ancestries.

PURPOSE: Monogenic rare diseases contribute significantly to infant deaths and pediatric hospitalizations and cause burden to the patients and their families. The American College of Medical Genetics and Genomics recommended in 2021 that carrier screening of autosomal recessive and X-linked conditions with a carrier frequency of ≥1/200 and a severe or moderate phenotype should be offered when planning or during pregnancy. In November 2023 gnomAD v4.0 was released. It contains in total 807,162 individuals, being nearly 5× larger than previous versions, which have been used to estimate gene carrier frequencies (GCF). METHODS: We utilized gnomAD v4.0 (GRCh38) to calculate the GCFs for available genetic ancestry groups for variants having pathogenic or likely pathogenic classification (>80% of submissions) in ClinVar. We calculated GCF separately for exomes and genomes, combined data, and at-risk couple frequencies (ACF) per genetic ancestry group. RESULTS: In total, 324 genes had a GCF ≥1/200 in at least 1 ancestry subgroup. The number of genes with GCF ≥1/200 varied greatly between subgroups. ACFs were more similar, Ashkenazi Jewish having the highest ACF of 6.11%. CONCLUSION: Improved understanding of carrier risks and updated carrier screening content would allow patients to make more informed reproductive decisions.

Humans↗

Novel splice-site and recurrent p.Arg729* CNKSR2 variants in ESES/CSWS: insights into sex-dependent expression.

PURPOSE: Pathogenic variants in CNKSR2 (Xp22.12) cause an X-linked neurodevelopmental disorder with intellectual disability, language impairment, and a distinctive epilepsy phenotype, including encephalopathy with status epilepticus during slow-wave sleep (ESES/CSWS). Hemizygous males are typically severely affected, whereas symptomatic females remain rare and incompletely characterized. We describe two unrelated patients with de novo CNKSR2 variants to expand the mutational and sex-dependent phenotypic spectrum of this disorder. METHODS: Both patients underwent clinical, electroencephalographic, and neuroimaging evaluation. CNKSR2 variants were identified by whole exome sequencing with parental segregation, and the splice-site variant was assessed in silico (SpliceAI, MaxEntScan, Human Splicing Finder). RESULTS: Patient 1, a 17-year-old female, harbored a novel canonical splice-site variant (c.64+1G>A) in the N-terminal region and presented with a relatively mild phenotype. In silico analysis supported abolition of the canonical donor splice site. Patient 2, an 8-year-old male, carried a de novo nonsense variant (c.2185C>T, p.Arg729*) and exhibited drug-resistant ESES, autism, and severe language impairment. p.Arg729* had previously been reported in one independent male. Our case represents its second independent occurrence, a CGA>TGA transition at a CpG dinucleotide consistent with a mutational hotspot. CONCLUSION: Together, these cases expand the mutational spectrum and provide further evidence for sex-dependent phenotypic variability in CNKSR2-related epilepsy. Our observations support the hypothesis that X-chromosome inactivation may contribute to phenotypic variability in females, although XCI was not assessed here, and support inclusion of CNKSR2 in epilepsy gene panels regardless of sex.

Humans↗

Single-nucleus profiling reveals a core disease signature and cell type-specific vulnerabilities in early Rett syndrome.

Rett syndrome (RTT) is an X-linked neurological disorder caused by MECP2 mutations, creating distinct cellular environments in females (mosaic) versus males (nonmosaic). Despite female patients representing most cases, how mosaicism contributes molecularly to RTT pathogenesis, particularly in presymptomatic stages, remains poorly understood. To address this question, we profiled hippocampal transcriptomes of young female and male RTT mice using bulk and single-nucleus RNA sequencing. We identified a core disease signature of consistently dysregulated genes only in MeCP2- cells across RTT models. Moreover, we uncovered non-cell autonomous effects exclusively in female MeCP2+ excitatory neurons, suggesting that these circuits are more vulnerable early in the mosaic RTT environment. The single-nuclei data also revealed an underappreciated MeCP2- interneuron subtype that had the most transcriptional dysregulation in both male and female RTT hippocampi. Together, these data highlight the different effects of MeCP2 loss on excitatory and inhibitory circuits between the mosaic and nonmosaic environments in early RTT pathogenesis.

Rett Syndrome↗

Granulopoietic Dysregulation in a Patient-Tailored Mouse Model of Barth Syndrome.

Barth syndrome (BTHS) is an X-linked recessive disorder characterized by cardiomyopathy, skeletal muscle myopathy and fatigue, growth restriction, and neutropenia. Neutropenia increases the risk of life-threatening bacterial infections, a major cause of death in individuals with BTHS. Currently, there is no curative treatment for BTHS or associated neutropenia. The development of therapeutic strategies to correct BTHS-associated neutropenia has been hindered by a limited understanding of the underlying molecular mechanisms involved. BTHS is caused by a mutation in the Tafazzin gene encoding a transacylase required for the maturation of cardiolipin, an inner mitochondrial membrane phospholipid crucial for mitochondrial structure and function. We introduced a BTHS patient's point mutation (TAZD75H) into the mouse Tafazzin enzyme's critical acyltransferase site using CRISPR/Cas9-mediated genome editing, resulting in a patient-tailored point mutant knock-in BTHS model (TazD75H) that expresses a stable mutant TazD75H protein lacking transacylase activity. TazD75H mice were then used to investigate how loss of Tafazzin enzymatic activity impacts hematopoiesis. Male TazD75H mice exhibited impaired granulopoiesis and neutropenia secondary to impaired function of hematopoietic progenitors. Furthermore, they demonstrated age-dependent neutrophil maturation impairment reflecting the variable neutropenia observed in BTHS patients. Additionally, male TazD75H mice exhibit chronic lymphopenia that persists post TazD75H bone marrow transplantation. Mechanistically, the TAZD75H point mutation caused hematopoietic cell mitochondrial dysfunction in patient-derived immortalized TAZD75H lymphoblasts, increasing reactive oxygen species production and mitochondrial membrane depolarization. Likewise, Cyclosporine A treatment rescued these mitochondrial phenotypes in vitro, confirming TAZD75H mitochondrial dysfunction. Overall, our findings demonstrate that mitochondrial dysfunction secondary to TAFAZZIN loss of enzymatic function underlies BTHS-associated neutropenia and lymphopenia.

Animals↗

X-linked ichthyosis with seizures, ADHD, and autism spectrum disorder: a case report with an uncommon clinical presentation.

INTRODUCTION AND IMPORTANCE: X-linked ichthyosis (XLI) is a genetic condition characterized by scaly skin due to steroid sulfatase (STS) deficiency, often associated with additional neurodevelopmental issues. CASE PRESENTATION: A 10-year-old male child was admitted to the dermatology department. The child had been born prematurely at 26 weeks' gestation with a low birth weight of 1.6 kg. He presented with seizures characterized by abnormal upper-limb movements and was diagnosed with congenital ichthyosis. The child exhibited delayed language and motor development, learning difficulties, microcephaly, and dry, scaly skin, which he habitually peeled and ingested. Genetic analysis (single-nucleotide polymorphism and combined comparative genomic hybridization) revealed a 1.65 Mb deletion on chromosome Xp22.31 affecting the STS gene and other adjacent genes. The patient had low STS enzyme activity (3.5 nmol/hour/protein) in adipose tissue. Neuroimaging showed no structural abnormalities, though an electroencephalogram indicated mild slowing. CLINICAL DISCUSSION: Given the established association between STS deletions and neurodevelopmental as well as psychiatric comorbidities, early recognition of emerging psychiatric features is essential. Given the established association between STS deletions and neurodevelopmental as well as psychiatric comorbidities, early recognition of emerging psychiatric manifestations is essential. Management should follow evidence-based recommendations for first-episode or early psychotic symptoms, emphasizing careful assessment, individualized pharmacological treatment when indicated, and multidisciplinary psychosocial support. Such an approach may improve clinical stabilization while avoiding premature diagnostic labeling. CONCLUSION: This case highlights the importance of early genetic diagnosis and personalized treatment approaches, integrating dermatological, neurological, and psychiatric care to optimize outcomes in XLI.

X-linked ichthyosis↗

Studies on the female sterile mutant rudimentary of Drosophila melanogaster. II. An analysis of aspartate transcarbamylase and dihydroorotase activities in wild-type and rudimentary strains.

The activities of the enzymes aspartate transcarbamylase (ATCase) and dihydroorotase (DHOase) were determined in adult females from a wild-type strain and from eight different alleles of the X-linked mutation rudimentary (r) of Drosophila melanogaster. The alleles chosen span the genetic map of the r locus. The characteristics of the DHOase-catalyzed reaction which converts carbamyl aspartate to dehydroorotate are briefly described. Of all of the r strains tested, only one, r9, has wild-type levels of aspartate transcarbamylase and dihydroorotase activities. The other seven show either intermediate or very low levels of activity for both enzymes. The lowered ATCase and DHOase activities observed in mutants which do not map in the region of the structural gene for these enzymes are interpreted in light of recent evidence that ATCase and DHOase are part of a three-enzyme complex.

Alleles↗

Human Monocytic Models Reveal Genotype-Dependent Inflammatory Programs in VEXAS Syndrome.

OBJECTIVES: VEXAS syndrome is a severe X-linked autoinflammatory disorder caused by somatic mutations in ubiquitin-like modifier activating enzyme 1 (UBA1), with clinical outcomes that vary by UBA1 genotype. We aimed to elucidate genotype-specific inflammatory programs and identify potential therapeutic targets. METHODS: We conducted longitudinal deep phenotyping, including whole-blood RNA sequencing (RNA-seq) and clinical activity assessment. Peripheral blood samples were analyzed by single-cell RNA-seq. Human monocytic cell lines harboring each major UBA1 mutation (p.Met41Val, p.Met41Thr, or p.Met41Leu) were generated and subjected to transcriptomic and functional analyses. RESULTS: Thirteen patients with VEXAS syndrome contributed a total of 79 RNA-seq samples. Among genes upregulated in VEXAS syndrome, RNASE1 showed the strongest correlation with longitudinal disease activity (r = 0.70, FDR < 0.05) and was upregulated in patients' monocytes. In UBA1-mutant monocytic cell lines, genotype-dependent ubiquitination defects were observed in a graded manner (p.Met41Val > p.Met41Thr > p.Met41Leu), even in the absence of exogenous stimuli. These defects were accompanied by unfolded protein response activation, increased pro-inflammatory cytokine production, progressive cell death, and RNASE1 upregulation, all following the same graded pattern, recapitulating patient genotype-phenotype associations. Transcriptomic analyses demonstrated enrichment of pro-inflammatory, interferon, and necroptosis signatures in more severe genotypes. Notably, inhibition of receptor-interacting protein kinase 3 (RIPK3) markedly attenuated all pathological features, including RNASE1 upregulation. CONCLUSIONS: Our UBA1-mutant monocytic cell-line models, representing three distinct genotypes, recapitulate genotype-dependent inflammatory phenotypes that can be modulated by RIPK3 inhibition, providing a translational platform for mechanistic investigation and precision therapy development in VEXAS syndrome.

Journal Article↗

Human GPR174 deficiency drives polyclonal lymphoproliferative disease via defects in T cell function.

The X-linked G-protein coupled receptor GPR174 is highly expressed in T and B lymphocytes and has immunoregulatory roles in mice, but its function in humans is unknown. We describe a cohort of six individuals who have function-disrupting variants in GPR174 and a clinical phenotype of lymphadenopathy and autoimmunity. Histological analysis of two patient lymph nodes revealed necrotizing lymphadenitis and lymphoproliferation resembling Kikuchi-Fujimoto disease. In-depth analysis of three patients and related carriers revealed overaccumulation of CD8 terminally differentiated effector memory cells re-expressing CD45RA (TEMRA). Patient cells and GPR174-deficient CD8 T cells generated from controls showed less repression of proliferation by the GPR174 ligand lysophosphatidylserine (lysoPS) and an effector-biased gene expression program. GPR174-deficient CD4 T cells were resistant to lysoPS-mediated suppression of IL2 production. In mice, chronic viral infection led to over-accumulation of GPR174-deficient effector CD8 T cells. We describe an inborn error of immunity associated with dysregulated lymphocyte responses that we propose predisposes to exaggerated lymphoproliferation and autoimmunity following viral infection.

Journal Article↗

X-linked recessive (Duchenne) muscular dystrophy (DMD) and purine metabolism: effects of oral allopurinol and adenylate.

Data are presented which suggest that Duchenne muscular dystrophy (DMD) may have some origin in a severe deficiency of total muscle adenine nucleotides. Using double-blind techniques, this possibility was tested in 16 DMD patients by giving oral allopurinol, a synthetic inhibitor of the purine catabolic enzyme xanthine oxidase. Sublingual procaine adenylate was also briefly tested. Instances of clinical improvement quickly occurred which were statistically significant; they were accompanied by a significant increase in physical strength. These improvements have been maintained for more than 6 mo by administration of a small amount of allopurinol daily. Procaine adenylate had little effect. These results support the above view of DMD and seem to indicate that existing purines, retained and recycled after allopurinol, can sustain such improvement, and that additional adenylate is unnecessary.

Adenosine Monophosphate↗

EGFLAM Pathogenic Variants and Congenital Stationary Night Blindness.

IMPORTANCE: Congenital stationary night blindness (CSNB) is a clinically and genetically heterogeneous inherited retinal disorder (IRD), and in many complete CSNB (cCSNB) cases, the underlying genetic cause remains unknown. Uncovering the genetic defects of IRDs helps to refine diagnostic methods and supports the development of specific therapeutic approaches. OBJECTIVE: To describe the phenotype and the underlying gene defect in patients with cCSNB from 2 unrelated families. DESIGN, SETTING AND PARTICIPANTS: This retrospective case series was conducted from January 2023 to July 2025. Data for 3 patients from cohorts of genetically unsolved IRD cases in France (n&#x2009;=&#x2009;140 for CSNB) and the Netherlands (n&#x2009;=&#x2009;2730 for IRD) were analyzed clinically and genetically. EXPOSURES: Complete ocular examination, including multimodal retinal imaging and full-field electroretinography (ffERG) incorporating the International Society for Clinical Electrophysiology of Vision standards and multimodal retinal imaging, were performed. Gene defects were identified by genome sequencing (GS) and exome sequencing (ES). MAIN OUTCOMES AND MEASURES: The main outcome was a gene defect, EGFLAM, underlying cCSNB. Measures included phenotyping, GS, ES, Sanger sequencing, and cosegregation analysis. RESULTS: The series included 3 patients from 2 unrelated families of Moroccan ancestry showing high myopia, reduced visual acuity, and night blindness. Retinal imaging depicted myopic changes. ffERG revealed electronegative Schubert-Bornschein configuration in keeping with cCSNB with ON-bipolar cell dysfunction. Patients were lacking pathogenic variants in known genes implicated in IRDs, including CSNB. Two different homozygous pathogenic variants, c.1563_1566del, p.(Val522Glufs*18) and c.1795C>T, p.(Arg599*) in EGFLAM were identified by ES and GS. The corresponding protein is localized in the outer plexiform layer and important for ON-bipolar cell signaling in the retina. CONCLUSION AND RELEVANCE: This case series reports on a gene defect in EGFLAM implicated in human cCSNB. Clinicians should be aware about this association and consider including EGFLAM in diagnostic gene panels for IRDs. This discovery may lead to faster and more accurate diagnosis of cCSNB and genetic counseling, as well as a pathway for developing therapies.

Adolescent↗

ATRX Condensates as Candidate Organizers of Enhancer-Centered Nuclear Microenvironments in Neural Progenitors: A Hypothesis for Enhancer-Associated ATRX Function in Neural Progenitors.

Neural progenitor cells (NPCs) must preserve lineage identity while remaining responsive to developmental cues. Here, we discuss the hypothesis that ATRX condensates help organize enhancer-centered nuclear microenvironments in NPCs. ATRX has long been studied in heterochromatin maintenance, histone variant deposition, and chromatin remodeling; earlier work has also shown that ATRX can occupy euchromatic and active regulatory regions and contribute to transcriptional regulation. Recent evidence in human NPCs indicates that ATRX forms nuclear puncta with condensate-like properties, associates with neurogenic enhancer-rich regions, and incorporates regulatory factors such as CHD7 and p300. Perturbation of ATRX condensate formation is associated with changes in enhancer-associated ATRX occupancy, neural gene-expression programs, and neuroepithelial organization, suggesting a regulatory mode that may complement canonical heterochromatin-associated functions. We propose a dual-mode model in which folded domains contribute to chromatin anchoring at repressive regions, whereas intrinsically disordered regions support condensate-associated organization at active developmental enhancers. We emphasize that whether ATRX condensates activate enhancers de novo, stabilize pre-existing enhancer states, buffer transcriptional variability, or primarily organize cofactor localization remains unresolved. We also discuss limitations of the current evidence and outline acute, locus-specific experiments needed to test the model.

X-linked Nuclear Protein↗

Comparative genomic landscape of lower-grade glioma and glioblastoma.

Biomarkers for classifying and grading gliomas have been extensively explored, whereas populations in public databases were mostly Western/European. Based on public databases cannot accurately represent Chinese population. To identify molecular characteristics associated with clinical outcomes of lower-grade glioma (LGG) and glioblastoma (GBM) in the Chinese population, we performed whole-exome sequencing (WES) in 16 LGG and 35 GBM tumor tissues. TP53 (36/51), TERT (31/51), ATRX (16/51), EFGLAM (14/51), and IDH1 (13/51) were the most common genes harboring mutations. IDH1 mutation (c.G395A; p.R132H) was significantly enriched in LGG, whereas PCDHGA10 mutation (c.A265G; p.I89V) in GBM. IDH1-wildtype and PCDHGA10 mutation were significantly related to poor prognosis. IDH1 is an important biomarker in gliomas, whereas PCDHGA10 mutation has not been reported to correlate with gliomas. Different copy number variations (CNVs) and oncogenic signaling pathways were identified between LGG and GBM. Differential genomic landscapes between LGG and GBM were revealed in the Chinese population, and PCDHGA10, for the first time, was identified as the prognostic factor of gliomas. Our results might provide a basis for molecular classification and identification of diagnostic biomarkers and even potential therapeutic targets for gliomas.

Humans↗

Human gene mapping using an X/autosome translocation.

Human fibroblasts containing a translocation between the X chromosome and chromosome 15 were fused with the 6-thioguanine-resistant mouse cell line, IR. Resulting hybrids, selected in HAT medium, retained the X/15 chromosome. Hybrids which were counterselected in 6-thioguanine lost this chromosome. The X-linked markers glucose-6-phosphate dehydrogenase (G6PD), phosphoglycerate kinase (PGK), and hypoxanthine phosphoribosyl transferase (HPRT), and the non-X-linked markers pyruvate kinase (PKM2) mannose phosphate isomerase (MPI), N-acetyl hexosaminidase A (HEXA) and beta2-microglubulin (beta2-m) all segregated in concordance with the X/15 translocation chromosome. The latter markers have been assigned to chromosome 15. Selection against the X/15 chromosome was done using antihuman beta2-m serum. Electrophoretic and immunochemical analyses of the N-acetyl hexosaminidases A and B in these hybrids were performed.

Acetylglucosaminidase↗

Epigenetic aging and autosomal methylation remodeling in Anderson-Fabry disease.

Anderson-Fabry disease (AFD) is a rare X-linked lysosomal storage disorder characterized by marked clinical heterogeneity and incompletely understood genotype-phenotype correlations. While X-chromosome inactivation has been extensively investigated, the contribution of autosomal epigenetic mechanisms to phenotypic variability remains poorly defined. Here, we performed an exploratory genome-wide DNA methylation analysis in 32 AFD patients (22 females and 10 males; mean age 51.7&#xa0;years) recruited within a multicenter regional research project in Calabria (Italy). DNA methylation profiling was conducted using the Infinium MethylationEPIC v2.0 array. The analysis integrated two complementary approaches: differential methylation analysis and evaluation of biological aging through multiple epigenetic clocks, including Horvath, Hannum, PhenoAge, Skin & Blood, GrimAge, and DunedinPACE. Exploratory methylome-wide analysis identified a limited set of CpG loci showing nominal evidence of methylation differences between carriers of pathogenic and non-pathogenic variants; however, none remained statistically significant after correction for multiple testing. Annotation of the top-ranking nominal CpG associations highlighted genes involved in biological processes including vascular regulation, intracellular trafficking, cytoskeletal organization, immune signaling, and lipid metabolism. No significant differences between groups were observed for the conventional epigenetic age-acceleration measures examined. In contrast, carriers of pathogenic variants showed significantly higher DunedinPACE values (p&#xa0;=&#xa0;0.0328), indicating a faster estimated pace of biological aging. This finding suggests that DunedinPACE may capture aspects of the cumulative systemic burden associated with pathogenic GLA variants, although confirmation in larger independent cohorts is required. Overall, this pilot epigenomic study provides preliminary evidence that autosomal epigenetic remodeling and biological aging acceleration may contribute to phenotypic heterogeneity in AFD.

Anderson-Fabry disease↗

Two iPSC lines with frameshift mutations in FTSJ1 as models for X-linked non-syndromic intellectual disability.

CRISPR/Cas9 was used to introduce two different FTSJ1 frameshift mutations into an existing human male iPSC line (UMGWi004-B). No additional genomic or chromosomal changes were detected. The modified iPSC express different stem cell markers and can be induced to differentiate into cells from all three germ layers. FTSJ1 is ubiquitously expressed and mutations in this X-chromosomal gene are involved in an intellectual developmental disorder (OMIM: #309549). These cells can be used to model the disease at the cellular and organoid level in their original state or after differentiation into cell types of interest.

Journal Article↗