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PubMed2026

C-Terminal Truncation and Fusion Partner Determine Oncogenicity of FGFR3.

UNLABELLED: Genomic alterations affecting components of the fibroblast growth factor (FGF) signaling axis can trigger aberrant pathway activation and tumor development. Genomic truncation of the FGF receptor 2 (FGFR2) exon 18 (E18) disrupts the FGFR2 carboxy (C)-terminal tail, acting as a potent driver alteration across multiple tumor types. In this study, we analyzed human oncogenomic datasets to reveal that E18 truncations are similarly prevalent in FGFR3, an FGFR2 paralog. FGFR3 E18 truncations primarily occur due to rearrangements (RE) that involve transforming acidic coiled-coil-containing protein 3 (TACC3), resulting in FGFR3ΔE18-TACC3 gene fusions. In contrast to E18-truncated FGFR2, functional in vitro and in vivo examination of Fgfr3 variants demonstrated that the truncation of Fgfr3 E18 is insufficient to promote oncogenic activity in cell lines or in the lungs and mammary glands of mice. Only the combination of an Fgfr3 E18 truncation with a RE partner gene that encodes a receptor-dimerizing domain resulted in the development of tumors, which were sensitive to FGFR inhibition. Overall, these findings suggest that patients with cancers that are positive for rearranged FGFR3, resulting in E18 truncation and a fusion to dimerizing partners, should be considered for FGFR-targeted therapies. SIGNIFICANCE: FGFR3, unlike its paralog FGFR2, requires both a C-terminal truncation and fusion to a partner gene that retains the expression of a dimerizing domain to effectively drive oncogenic signaling and tumorigenesis.

Receptor, Fibroblast Growth Factor, Type 3↗

PubMed2026

CHAMP1-Related Neurodevelopmental Disorder: Two Turkish Cases with Novel Truncating Variants and Literature Review.

INTRODUCTION: CHAMP1-related neurodevelopmental disorder (CHAMP1-NDD; neurodevelopmental disorder with hypotonia, impaired language, and dysmorphic features; MIM: 616579) is a rare autosomal-dominant condition caused by de novo truncating variants leading to haploinsufficiency. The phenotype is characterized by global developmental delay, intellectual disability, severe speech impairment, hypotonia, distinctive craniofacial features, and variable multisystem involvement. CASE PRESENTATION: We describe two unrelated girls harboring novel de novo truncating CHAMP1 variants. Both presented with global developmental delay, profound speech impairment, hypotonia, postnatal growth impairment, and characteristic craniofacial features. Neuroimaging demonstrated normal findings in 1 patient and a thin corpus callosum in the other. Additional manifestations included high-grade vesicoureteral reflux in one individual and sensory dysregulation, reduced pain sensitivity, early-onset hyperphagia, and recurrent respiratory infections in the other. Perinatal complications were noted in one case; however, the overall phenotype was considered primarily attributable to the underlying genetic diagnosis. Exome sequencing identified heterozygous truncating variants, NM_032436.4:c.2081_2082del; p.Ser694* and NM_032436.4:c.2062dup; p.Glu688Glyfs*8, both confirmed as de novo and classified as likely pathogenic according to American College of Medical Genetics and Genomics (ACMG) criteria. CONCLUSION: These cases expand the mutational spectrum of CHAMP1 and further delineate the phenotypic variability of this disorder, highlighting under-recognized systemic and behavioral features. Recognition of these additional clinical observations may facilitate earlier diagnosis and multidisciplinary management, although further studies in larger cohorts are required to clarify their clinical relevance.

CHAMP1↗

PubMed2026

RBM20 Truncating Variants and Human Cardiomyopathy.

IMPORTANCE: Genetic diagnosis has become increasingly important to guide clinical decision-making for patients with dilated cardiomyopathy (DCM). Pathogenic or likely pathogenic (P/LP) missense variants in the gene RBM20 cause a highly penetrant arrhythmogenic DCM, but the role of RBM20 truncating variants (RBM20tvs) is unclear. OBJECTIVE: To assess the contribution of RBM20 variants to arrhythmogenic DCM. DESIGN, SETTING, AND PARTICIPANTS: In this cohort study, participants in the genome-first UK Biobank (UKB) and All of Us populations were evaluated to assess the etiologic fraction, natural history and penetrance of RBM20 variants. Retrospective data were collected from an international cohort of patients with DCM and RBM20 variants identified at centers of excellence for genetic heart disease and compared based on time to event. Study dates are not disclosed because the institutional review board did not authorize the sharing of this information. EXPOSURES: RBM20 variants were compared to known P/LP variants and variants of uncertain significance in RBM20 as well as titin truncating variants (TTNtvs). MAIN OUTCOMES AND MEASURES: Major ventricular arrhythmias, end-stage heart failure, and heart failure hospitalization as measured by medical record review (retrospective cohort) and diagnostic codes (UKB). RESULTS: Two main cohorts were studied for this project. In UK Biobank, a cohort of participants with RBM20tvs, RBM20 synonymous variants, and TTNtvs was studied. Of these 4249 participants, 1869 (44%) were male. The mean (SD) age at enrollment was 56 (8.2) years. In the RBM20 registry, of 179 patients, 105 (58.6%) were male, and the mean (SD) age at enrollment was 43.8 (19.1) years. A validation cohort from the All of Us biobank was also used. This consisted of 7002 participants, 4342 of whom (62.0%) were male, and the mean (SD) age was 52.7 (16.7) years. The etiologic fraction of RBM20 variants in arrhythmogenic DCM was 0.53 (95% CI, 0.32-0.67; P < .001). In genome-first biobanks, lifetime incidence of cardiomyopathy, heart failure, or major ventricular arrhythmia diagnosis was lower in participants with RBM20 variants than in those with TTNtvs (hazard ratio, 0.55; 95% CI, 0.36-0.84; P < .001). Patients with RBM20tvs and DCM presented to referral centers later in life than those with P/LP RBM20 and DCM (mean [SD], 53 [10] vs 34 [18] years; P < .001) and were less likely to have a family history of sudden cardiac arrest (2 of 10 [20%] vs 11 of 17 [65%]; P = .046) or cardiomyopathy (2 of 10 [20%] vs 14 of 18 [78%]; P < .001). There was no significant difference in age- and sex-adjusted incident major heart failure or arrhythmia events between patients with RBM20tv and DCM or those with P/LP RBM20 and DCM, though sex-adjusted lifetime hazard was reduced in those with RBM20tv and DCM (hazard ratio, 0.13; 95% CI, 0.03-0.56; P = .01). CONCLUSIONS AND RELEVANCE: This study found that RBM20 variants contributed to arrhythmogenic DCM phenotypes but conferred reduced lifetime disease penetrance compared to TTNtvs and milder disease severity alone than P/LP RBM20 variants. Their potential for additive interactions with other damaging variants should be considered in patients with DCM and their families.

Humans↗

PubMed2026

A truncated COL10A1 protein causes Schmid metaphyseal chondrodysplasia via protein downregulation and impairing α1 trimer formation and secretion.

Schmid-type metaphyseal chondrodysplasia (SMCD) is primarily caused by mutations in the COL10A1 gene. This study reports a novel frameshift mutation, c.1940dup (p.Asn647Lysfs*2), identified in a Chinese SMCD pedigree. The mutation did not alter messenger RNA levels but significantly reduced COL10A1 protein expression. The mutant protein lacks the C-terminal 33 amino acids, resulting in a truncated polypeptide of 648 residues with a lower molecular weight than the wild-type protein. Degradation kinetics analysis showed no evidence of accelerated turnover. Notably, even under complete inhibition of degradation pathways, mutant protein expression remained substantially lower than that of wild-type, suggesting a potential defect in translational efficiency. Furthermore, the mutation severely disrupted the assembly of the characteristic collagen X trimer and led to markedly reduced extracellular secretion, as measured by accumulated protein levels in conditioned medium. These findings demonstrate that the c.1940dup mutation contributes to SMCD pathogenesis through coordinated mechanisms involving protein truncation, reduced expression, probable translational deficiency, and defective trimer formation and secretion, thereby revealing new potential therapeutic targets.

Osteochondrodysplasias↗

PubMed2026

Clinical and immunological characterization of a child with a homozygous TBK1 kinase-domain truncation.

TBK1 is a serine-tyrosine kinase protein that transmits signals from pattern recognition receptors to the NF-κB pathway leading to production of Type 1 Interferons. Mutations in this protein have been associated with arthritis, vasculitis, herpes simplex encephalitis and amyotrophic lateral sclerosis. In the current study, we characterized the functional consequences of a TBK1-variant bearing a truncation in exon 4 and 5 in a patient with poly arthritis resembling juvenile idiopathic arthritis and necrotizing encephalitis. The truncation was associated with reduced TBK1 protein abundance and altered phosphorylation. The variant was associated with increased basal/and or Poly-I: C induced IL-6, TNFα, IL-1β and IL-18 and type 1 Interferon ex vivo. Our findings expand the phenotypic spectrum of TBK1 loss-of-function variants and may provide insight into the management of immune dysregulation in affected patients.

Child↗

PubMed2026

Incidence of Atrial and Ventricular Arrhythmias in Patients With Titin Truncating Variants Across the Ventricular Morphofunctional Phenotypic Spectrum.

BACKGROUND: Titin truncating variants (TTNtvs), the most common genetic cause of dilated cardiomyopathy (DCM), are over-represented in early-onset atrial fibrillation (AF) and unexplained sudden cardiac arrest/death (SCA/SCD), suggesting they can cause arrhythmias before development of overt ventricular cardiomyopathy. OBJECTIVES: This study sought to compare the incidence of atrial and ventricular arrhythmias (VAs) between TTNtv-positive patients with genotype-positive but phenotype-negative (G+/P-) disease, nondilated left ventricular cardiomyopathy (NDLVC), and DCM. METHODS: A retrospective review of 1,229 patients in our Arrhythmogenic/Dilated Cardiomyopathy Registry was used to identify those with pathogenic/likely pathogenic TTNtvs. Patients were classified as having G+/P- disease, NDLVC, or DCM using the 2023 European Society of Cardiology guideline for cardiomyopathies. The incidence of AF, sustained VA, appropriate defibrillator therapies, SCA, and SCD was ascertained from medical records. RESULTS: Among 253 TTNtv-positive patients (mean age of 45 ± 16 years; 59% male), 54 (21%) were G+/P-, 49 (20%) were NDLVC, and 150 (59%) were DCM. During a median follow-up of 3.8 years at our institution, new-onset AF was seen in 67 patients (26% of those at risk). There was no significant difference in survival from new-onset AF in patients with NDLVC (HR: 3.29; 95% CI: 0.71-15.3; P = 0.13), although DCM was associated with worse AF-free survival (HR: 4.86; 95% CI: 1.17-20.1; P = 0.03). New-onset VAs were seen in 44 (17%) patients during follow-up, including SCA in 12 (5%) patients. There was no association between NDLVC (HR: 0.71; 95% CI: 0.19-2.69; P = 0.62) and DCM (HR: 0.97; 95% CI: 0.37-2.54; P = 0.95) phenotypes compared with G+/P- patients. Cardiac transplantation was done in 14 (6%) patients, and 6 (2%) died of cardiac causes, including 2 cases of SCD. CONCLUSIONS: When stratified by morphofunctional phenotype, there was no difference in VAs across morphofunctional phenotypes in patients with TTNtvs. This highlights that patients with TTNtvs may be at risk of SCA/SCD even without overt ventricular cardiomyopathy. The risk of new-onset AF was highest in patients with DCM but was seen at all phenotypic stages during follow-up.

arrhythmia↗

PubMed2024

ASXL1 truncating variants in BOS and myeloid leukemia drive shared disruption of Wnt-signaling pathways but have differential isoform usage of RUNX3.

BACKGROUND: Rare variants in epigenes (a.k.a. chromatin modifiers), a class of genes that control epigenetic regulation, are commonly identified in both pediatric neurodevelopmental syndromes and as somatic variants in cancer. However, little is known about the extent of the shared disruption of signaling pathways by the same epigene across different diseases. To address this, we study an epigene, Additional Sex Combs-like 1 (ASXL1), where truncating heterozygous variants cause Bohring-Opitz syndrome (BOS, OMIM #605039), a germline neurodevelopmental disorder, while somatic variants are driver events in acute myeloid leukemia (AML). No BOS patients have been reported to have AML. METHODS: This study explores common pathways dysregulated by ASXL1 variants in patients with BOS and AML. We analyzed whole blood transcriptomic and DNA methylation data from patients with BOS and AML with ASXL1-variant (AML-ASXL1) and examined differential exon usage and cell proportions. RESULTS: Our analyses identified common molecular signatures between BOS and AML-ASXL1 and highlighted key biomarkers, including VANGL2, GRIK5 and GREM2, that are dysregulated across samples with ASXL1 variants, regardless of disease type. Notably, our data revealed significant de-repression of posterior homeobox A (HOXA) genes and upregulation of Wnt-signaling and hematopoietic regulator HOXB4. While we discovered many shared epigenetic and transcriptomic features, we also identified differential splice isoforms in RUNX3 where the long isoform, p46, is preferentially expressed in BOS, while the shorter p44 isoform is expressed in AML-ASXL1. CONCLUSION: Our findings highlight the strong effects of ASXL1 variants that supersede cell-type and even disease states. This is the first direct comparison of transcriptomic and methylation profiles driven by pathogenic variants in a chromatin modifier gene in distinct diseases. Similar to RASopathies, in which pathogenic variants in many genes lead to overlapping phenotypes that can be treated by inhibiting a common pathway, our data identifies common pathways for ASXL1 variants that can be targeted for both disease states. Comparative approaches of high-penetrance genetic variants across cell types and disease states can identify targetable pathways to treat multiple diseases. Finally, our work highlights the connections of epigenes, such as ASXL1, to an underlying stem-cell state in both early development and in malignancy.

Humans↗

PubMed2010

Gene therapy of mdx mice with large truncated dystrophins generated by recombination using rAAV6.

Recombinant adeno-associated viral (rAAV) vector-mediated gene transfer represents a promising approach for many diseases. However, the applicability of rAAV vectors has long been hindered by the small (~4.8 kb) DNA packaging capacity. This limitation can hamper the packaging and delivery of critical regulatory elements and/or larger coding sequences, such as the ~14-kb dystrophin complementary DNA (cDNA) that is of interest for gene therapy of Duchenne muscular dystrophy (DMD). Here, we have demonstrated reconstitution of an expression cassette (7.3 kb) encoding a highly functional "minidystrophin" protein (ΔH2-R19, 222 kd) in vivo following intravascular co-delivery of two independent rAAV6 vectors sharing a central homologous recombinogenic region of 372 nucleotides. Similar to previously reported trans-splicing approaches, one rAAV vector provides the promoter with the ~1/2 initial portion of minidystrophin, while the second vector provides the remaining minidystrophin cDNA followed by the polyadenylation signal. Significantly, administering a modest dose [2 × 10(12) vector genomes (vg)] of the two minidystrophin-encoding rAAV vectors to dystrophic mice elicited an improvement of physiological performance indicative of prevention or amelioration of the disease state. These studies provide evidence that functional dystrophin transgenes larger than that typically carried by a single rAAV genome can be reconstituted in vivo by homologous recombination (HR) following intravascular co-delivery with rAAV6.

Animals↗

PubMed2026

A novel truncating FBN1 variant in a family with Marfan syndrome.

Marfan syndrome is caused by pathogenic variants in FBN1. We identified a novel heterozygous frameshift variant in FBN1 (NM_000138.5: c.6784_6787del, NP_000129.3:p.(Gln2262TrpfsTer28)) in an adult male with severe cardiovascular manifestations. The variant was absent from population databases and fulfilled PVS1 and PM2 criteria. This finding expands the mutational and phenotypic spectrum of FBN1 and highlights the clinical utility of genetic testing in family-based clinical management of Marfan syndrome.

Journal Article↗

PubMed2025

Clinicopathologic and genomic analyses of SMARCA4-mutated non-small cell lung carcinoma implicate the needs for tailored treatment strategies.

BACKGROUND: The clinicopathologic and therapeutic significance of SMARCA4 mutation in non-small cell lung carcinoma (NSCLC) remains unclear. METHODS: We retrieved 575 NSCLC cases from the clinical target sequencing cohort (N = 2157) to compare the clinicopathologic characteristics of groups subclassified based on the presence of truncated or non-truncated SMARCA4 mutations (SMARCA4-truncated, SMARCA4-non-truncated, and SMARCA4-wild type [WT]). The differences in gene expression profiles between these groups were evaluated using the TCGA-LUAD dataset. RESULTS: Fifty (2.3%) SMARCA4-truncated and 63 (2.9%) SMARCA4-non-truncated NSCLCs were identified. The majority of SMARCA4-truncated NSCLCs were present in male smokers (94.0%) and pathologically diagnosed as adenocarcinoma (76.0%). The SMARCA4-truncated group showed rare targetable driver alterations with a higher tumor mutation burden than the SMARCA4-WT group. Gene expression profile analysis revealed that cancer/testis antigen (CTA) expression was enriched in the SMARCA4-truncated group, with up to 57% of the cases displaying immunoreactivities for MAGEA4, CT45A, and/or PRAME. The SMARCA4-non-truncated group showed heterogeneous clinicopathologic, genomic, and immunohistochemical features that fell between SMARCA4-truncated and WT groups. Both SMARCA4-truncated and non-truncated groups showed significantly poor prognosis with pemetrexed-platinum chemotherapy, yet there was no significant difference in survival following immune checkpoint inhibitor monotherapy. CONCLUSION: SMARCA4-truncated NSCLC represents a variant of driver-negative NSCLC, mainly occurring in male smokers with poorly differentiated adenocarcinoma histology. In contrast, SMARCA4-non-truncated NSCLC indicates a heterogeneous subpopulation, exhibiting intermediate characteristics between the SMARCA4-truncated and SMARCA4-WT groups. While showing poor response to pemetrexed-platinum chemotherapy, increased CTA expression could be a novel therapeutic target in SMARCA4-mutated NSCLCs.

Humans↗

PubMed2026

A Common CD36 Variant and the Genetic Landscape of Dilated Cardiomyopathy in Individuals of African Ancestry.

IMPORTANCE: Dilated cardiomyopathy (DCM) is a major cause of heart failure that disproportionately affects individuals of African genetic ancestry (AFR), among whom familial clustering of disease is also more pronounced relative to those of European ancestry (EUR). However, established monogenic DCM genes, identified primarily in EUR populations, explain a smaller proportion of DCM cases in AFR populations. A recent study identified a common AFR-specific nonsense variant in CD36 that accounts for a substantial burden of DCM in AFR. How the risk and population impact of this variant compare with those of established genetic causes of DCM is unknown. OBJECTIVE: To compare the contribution of a CD36 nonsense variant to DCM risk with that of truncating variants in TTN and pathogenic or likely pathogenic (P/LP) variants in other established DCM genes. DESIGN SETTING AND PARTICIPANTS: Multicohort genetic association study including AFR and EUR participants with exome or genome sequence and DCM case status from four datasets: All of Us, Million Veteran Program, Penn Medicine Biobank, and the DCM Precision Medicine Study. EXPOSURE: Carrier status for TTN truncating variants, P/LP variants in 11 high confidence DCM genes, and the CD36 nonsense variant (Y325*; 0, 1, or 2 copies). MAIN OUTCOMES AND MEASURES: Odds of DCM; prevalence of risk-variant carriers among DCM cases; and population attributable fraction (PAF) for DCM. RESULTS: Among 82,623 AFR individuals across four studies, the mean age was 53.4 years and 1,625 had DCM. CD36 Y325* risk-allele homozygotes had 4.8-fold (95% CI, 3.1-7.3) increased odds of DCM, and CD36 Y325* heterozygotes had 1.4-fold (95% CI, 1.2-1.7) increased odds. TTN truncating variants also conferred elevated risk of DCM in AFR participants (OR, 8.46; 95% CI, 5.3-12.3). Among AFR DCM cases, 2.5% were CD36 homozygotes, second only to TTN truncating variants (4.3%) and exceeding all other high-confidence DCM genes combined (1.5%). In population-level analyses incorporating both heterozygous and homozygous CD36 Y325* carriers, the population-attributable fraction for CD36 (9.0%) surpassed that of TTN truncating variants (3.6%). CONCLUSIONS AND RELEVANCE: An ancestry-specific CD36 variant contributes more to DCM burden in AFR ancestry than established DCM genes, including TTN truncating variants, typically considered the most common genetic cause of DCM. These findings reshape the known genetic architecture of DCM in individuals of African ancestry and highlight the importance of representation in genomic research.

Journal Article↗

PubMed2026

Decreased TXNRD1 is associated with resistance to tagraxofusp in blastic plasmacytoid dendritic cell neoplasms, as seen in phase II.

Tagraxofusp is a CD123-targeted therapy comprised of a recombinant human interleukin-3 (IL-3) fused to a truncated diphtheria toxin payload. It is the first approved treatment specifically for patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN). To identify biomarkers of response, bone marrow samples from 12 BPDCN patients who were treated with tagraxofusp in the pivotal phase II trial (NCT02113982) were profiled longitudinally using a gene panel and single-cell RNA sequencing. Residual tumor cells following tagraxofusp expressed lower levels of TXNRD1 that would reduce the efficacy of tagraxofusp. In support of this, enzymatic inhibition of TXNRD1 resulted in higher viability of CAL-1 BPDCN cells following tagraxofusp. Responders had either wild-type or missense TET2 mutations, while transient and non-responders had at least one truncating TET2 mutation. Examples of these mutations within the catalytic domain of TET2 were constructed and transduced into cells. Missense and truncating mutants displayed reduced sensitivities to hypomethylating agents and prolonged S-phase stasis. These results suggest that the levels of TXNRD1 interact with intrinsic TET2 truncating mutations within the bone marrow to modulate patient response to tagraxofusp.

Female↗

PubMed2026

Alpha protein kinase 3 gene therapy restores heart function in mouse and human models of cardiomyopathy.

Truncating variants in the ALPK3 gene (encoding alpha protein kinase 3) cause severe cardiomyopathy for which no curative treatment exists1-3. Here we establish an adeno-associated virus (AAV)-mediated gene replacement therapy to deliver full-length human ALPK3. AAV-ALPK3 prevented disease in neonatal Alpk3-mutant mice and reversed established pathology in adults, with proteomic analysis demonstrating reversal of more than 95% of the molecular disease signature. Beyond ALPK3 deficiency, we explored broader therapeutic potential based on ALPK3's regulatory role in proteostasis, a pathway commonly disrupted across cardiomyopathies. ALPK3 expression is reduced in cardiomyocytes with TTN-truncating variants, the most prevalent cause of dilated cardiomyopathy, and the encoded titin protein has a protein quality control network in common with ALPK3. AAV-ALPK3 restored contractile function in human cardiac organoids with an ALPK3- or TTN-truncating variant. These findings provide proof of concept for ALPK3 gene therapy in patients with ALPK3 cardiomyopathy and reveal potential for indication expansion to cardiomyopathies associated with TTN-truncating variants, which are not amenable to gene replacement therapy due to size limitations.

Animals↗

PubMed2025

Quantifying evidence for phenotypic specificity (PP4) for syndromic phenotypes: Large-scale integration of rare germline FH variants from diagnostic laboratory testing for HLRCC and renal cancer.

PURPOSE: Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a rare cancer susceptibility syndrome exclusively attributable to pathogenic variants in FH (HGNC:3700). This article quantitatively weights the phenotypic context (PP4/PS4) of such very rare variants in FH. METHODS: We collated clinical diagnostic testing data on germline FH variants from 387 individuals with HLRCC and 1780 individuals with renal cancer and compared the frequency of "very-rare" variants in each phenotypic cohort with 562,295 population controls. We generated pan-gene very rare variant likelihood ratios (PG-VRV-LRs), domain-specific likelihood ratios for missense variants (DS-VRMV-LR) using spatial clustering analysis, and log2.08 likelihood ratios (LLRs) as applicable within the updated American College of Medical Genetics and Genomics/Association for Molecular Pathology variant classification framework. RESULTS: For HLRCC, the PG-VRV-LR was estimated to be 2669.4 (95% CI 1843.4-3881.2, LLR 10.77) for truncating variants and 214.7 (95% CI 185.0-246.9, LLR 7.33) for missense variants. For renal cancer, the PG-VRV-LR was 95.5 (95% CI 48.9-183.0, LLR 6.23) for truncating variants and 5.8 (95% CI 3.5-9.3, LLR 2.39) for missense variants. Clustering analysis in HLRCC cases revealed 3 "hotspot" regions wherein the DS-VRMV-LR increased to 1226.9. CONCLUSION: These data provide quantitative measures for very rare missense and truncating variants in FH, which reflect the differing phenotypic specificity of HLRCC and renal cancer and may be applicable in clinical variant classification.

Humans↗

PubMed2026

Generation of two induced pluripotent stem cell lines from dilated cardiomyopathy patients with TTN mutations.

Titin (TTN) encodes the largest protein in the human body and is essential for sarcomere assembly and muscle mechanosensation. Truncating TTN mutations are a leading cause of dilated cardiomyopathy (DCM). Here, we generated two induced pluripotent stem cell (iPSC) lines from female DCM patients, each carrying a heterozygous nonsense point mutation that produces a truncated titin protein. Both lines were reprogrammed from peripheral blood mononuclear cells (PBMCs) and characterized for expression of undifferentiated human iPSC state markers, tri-lineage differentiation capacity, and genomic integrity by copy-number analysis. These lines provide a patient-derived platform for investigating the mechanobiological basis of titin-truncation DCM in vitro.

Humans↗

PubMed2026

L2 β-lactamase contributes to ceftolozane-tazobactam resistance in Pseudomonas aeruginosa.

The prevalence of non-susceptibility to ceftolozane-tazobactam (C/T) among Pseudomonas aeruginosa remains low, but novel mechanisms of C/T resistance are of concern. Herein, we describe a novel P. aeruginosa genotype associated with high-level C/T resistance (>256/4 µg/mL) in a single patient. Whole-genome sequencing of the isolate was compared to that of a susceptible isolate cultured from the same patient 2 months earlier. Analysis of the sequences revealed two different P. aeruginosa high-risk clones: sequence type (ST)111 followed by ST235. The C/T-resistant ST235 isolate contained five copies of a genetic element composed of an L2 β-lactamase gene (blaL2) and a truncated ampRL2 transcriptional regulator gene, which are commonly found together in Stenotrophomonas maltophilia strains and have not been reported to mediate resistance to C/T. Comparative genomic analysis with other P. aeruginosa isolates failed to identify alternative explanations for the observed C/T resistance. We found that exogenous expression of blaL2 increased C/T minimum inhibitory concentrations (MICs) in genetically distinct P. aeruginosa strains. A screen of our archived isolates identified two P. aeruginosa clinical isolates, PS2045 and PS2046, with one and two copies, respectively, of the genetic element containing blaL2 and truncated ampRL2. Interestingly, disruption of the gene blaL2 but not the truncated ampRL2 in PS2045 led to a decrease in C/T MIC. Thus, we report a novel mechanism of C/T resistance in P. aeruginosa partially mediated by an L2 β-lactamase independently of its canonical regulator, AmpRL2.

bioinformatics↗

PubMed2026

Clinical and molecular characterization of TCF12 variants in an Asian pediatric cohort with craniosynostosis.

BACKGROUND: Craniosynostosis is a genetically heterogeneous craniofacial disorder caused by the premature fusion of one or more cranial sutures. Pathogenic variants in TCF12, encoding a basic helix-loop-helix (bHLH) transcription factor, represent a major cause of autosomal dominant coronal craniosynostosis and are characterized by incomplete penetrance and marked phenotypic variability. However, clinical and molecular data from Asian pediatric populations remain limited. METHODS: Trio-based whole-exome sequencing was performed on ten pediatric patients with cranial deformities and their parents. The identified TCF12 variants were classified according to the American College of Medical Genetics and Genomics (ACMG) guidelines and validated by Sanger sequencing. Detailed clinical and radiological data were collected. In addition, a comprehensive literature review was conducted to summarize previously reported TCF12 variants and associated phenotypes. RESULTS: Ten distinct heterozygous TCF12 variants were identified in ten unrelated pediatric patients, all of which were classified as pathogenic or likely pathogenic according to ACMG criteria. Six variants were inherited, and four occurred de novo. Seven patients had imaging-confirmed craniosynostosis, predominantly involving the coronal sutures (five bilateral and one unilateral), while one patient presented with multisuture craniosynostosis (left coronal and sagittal sutures). Three patients showed cranial deformities without radiographic evidence of suture fusion. Phenotypic heterogeneity and incomplete penetrance were observed, including a mildly affected parent. Most pathogenic variants were truncating variants distributed mainly across exons 14-19 and predicted to induce loss of function, either through nonsense-mediated mRNA decay or the production of truncated proteins lacking the entire C-terminal bHLH domain. Structural modeling analysis further indicated that the bHLH-domain-located missense variant p.Arg603Trp alters the local DNA-binding conformation of TCF12 and impairs its binding affinity to the E-box DNA motif. CONCLUSIONS: This study provides additional clinical and molecular data on TCF12-related craniosynostosis in a pediatric cohort from an Asian population. Our findings support haploinsufficiency as the central pathogenic mechanism, primarily driven by truncating variants affecting the C-terminal bHLH domain. The marked clinical heterogeneity, the presence of mild or evolving phenotypes, and incomplete penetrance observed in our cohort underscore the importance of early diagnosis and longitudinal clinical surveillance in affected families.

Humans↗

PubMed2026

Novel genetic variants identification and immune profiling in ataxia telangiectasia patients.

BACKGROUND: Ataxia telangiectasia (AT) is an autosomal recessive neurodegenerative disease. While heterozygous relatives of AT patients are known to be clinically healthy, a predisposition to various pathologies has been reported. Our aim was firstly, to further characterize the clinical features and broaden the spectrum of genetic pathogenic variants in AT patients. Secondly, we aimed to study the immune profiles of AT patients and their relatives to identify similarities or common biomarkers. METHODS: A Target Gene Sequencing for six patients suspected with AT was performed. Computational analysis was conducted to assess the pathogenicity of novel variants. The distribution of immune cells was assessed by flow cytometry in patients with AT, AT-like disorder, Friedreich ataxia, and in AT relatives. The expression pattern of candidate genes was evaluated by RT-qPCR. RESULTS: We identified and predicted the pathogenicity of novel variants in the ATM gene. Computational analysis suggested that the novel identified missense mutation could affect ATP binding pattern and ATM protein flexibility, while Alu element insertion could probably induces a premature stop codon. Furthermore, our results confirm the pathogenic effect of identified splicing mutations on the ATM transcript. Moreover, we noticed a high percentage of LTCD4 + and LTCD8 + senescent subsets in AT patients and a relative increase of the of intermediate and non-classical monocytes accompanied with a decrease of classical monocytes specifically in AT patients with truncated biallelic mutations which was intriguingly similar to the immune profile of AT parents. In addition, a difference of immune pattern was observed between AT patients with biallelic truncated mutations compared to those with at least one non-truncated mutation, with a variability intragroup. Gene expression analysis identified FOXO3, IL33 and METTL3 as putative genes that may yield clues into AT pathogenesis. CONCLUSION: Taken together, our study expands the mutational spectrum of AT disease worldwide and further characterize the immune profile of AT patients uncovering a possible difference in some immune cellular subsets related to ATM mutation type and delineate putative immune abnormalities related to ATM heterozygosity among AT parents. Furthermore, dysregulation in FOXO3, IL33 and METTL3 expression could be related to disease severity.

Humans↗