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Results for “Telomere Shortening”

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PubMed2025

An Immunosenescent CD8+ T Cell Subset in Patients with Axial Spondyloarthritis and Psoriatic Arthritis Links Spontaneous Motility to Telomere Shortening and Dysfunction.

OBJECTIVE: A pathogenetic role of CD8+ T lymphocytes in radiographic axial spondyloarthritis (r-axSpA) and other spondyloarthritis (SpA) is sustained by genome-wide association studies and by the expansion of public T cell clonotypes in the target tissues. This study investigates the migration of CD8+ T cells along with their phenotype and functions in patients with r-axSpA and psoriatic arthritis (PsA). METHODS: Peripheral blood CD8+ and CD4+ T cells were isolated from patients with r-axSpA (n = 128), PsA (n = 60), and rheumatoid arthritis (RA) (n = 74) and healthy donors (HDs) (n = 79). Transwell migration assay was performed in the presence of different chemokines. CD8+ T cell immunoprofiling and effector functions were assessed by multiparametric flow cytometry. Transcriptome signature was evaluated by RNA sequencing analysis, whereas telomere length and dysfunction were measured by reverse transcriptase-polymerase chain reaction and immunofluorescence-fluorescence in situ hybridization, respectively. RESULTS: A significantly higher number of CD8+ T cells migrating in the absence of chemokine stimuli was found in patients with SpA compared with HDs and patients with RA. This subset, producing cytotoxic (granzyme B, perforin, granulysin) and proinflammatory molecules (tumor necrosis factor), was significantly enriched in terminally differentiated (CCR7-CD45RA+) and senescent (CD28-CD57+) cells having a gene expression profile characterized by cytolytic signature and natural killer markers. Remarkably, these spontaneously migrating CD8+ T cells showed DNA damage response activation, telomere shortening, and dysfunction. CONCLUSION: These data describe a terminally differentiated CD8+ T cell subset with a senescent and cytotoxic/proinflammatory profile and an intrinsic invasive potential enriched in patients with SpA that represents a possible player in disease pathogenesis.

Humans↗

PubMed2026

Twisting the End Game: How Telomere Chromatin Modifications Shape Telomere Maintenance.

Cell division inevitably shortens telomeric DNA owing to the end-replication problem. Eukaryotic chromosomes possess specialized telomere structures to maintain genomic stability. In most proliferative cells, telomerase adds telomeric repeats during S-phase. In differentiated cells where telomerase is silenced, telomeres shorten progressively, thereby compromising genomic integrity. Consequently, cancer cells universally activate alternative telomere maintenance mechanisms during malignant transformation: ~80% reactivate telomerase, while a portion of the rest rely on BIR (break-induced replication)-mediated homologous recombination-based ALT (alternative lengthening of telomeres). Although these mechanisms are stable once established, the initial determinants influencing a cancer cell's choice remain poorly understood. This review discusses recent molecular insights into how telomeric chromatin properties profoundly impact this choice. After briefly introducing telomere chromatin characteristics and key players in its maintenance and dynamics, we discuss the mechanisms by which cancer cells acquire distinct telomere replication capabilities. In particular, we present an in-depth analysis linking telomere heterochromatin status to ALT. Furthermore, based on recent advances, we propose a coupled feedforward loop model explaining how the ALT state becomes "locked in" once initiated. Finally, we offer novel perspectives on rational, telomere-centric therapeutic interventions for ALT-positive cancers, focusing on strategies designed to disrupt such feedforward loops by manipulating telomeric chromatin structure.

Humans↗

PubMed2024

Concomitant telomere attrition is associated with spinal muscular atrophy in highly inbred region of North India: unraveling the thread in Kashmir region.

Spinal muscular atrophy (SMA) is a rare genetic disorder that unequivocally results in the degeneration of motor neurons, leading to muscle weakness and atrophy. This condition is caused by a mutation in the survival motor neuron 1 (SMN1) gene, which inevitably results in a deficiency of the SMN protein. In present study, we investigated the potential role of telomere attrition in SMA patients. Relative telomere length in peripheral blood lymphocytes was measured by Monochrome Multiplex Quantitative Polymerase Chain Reaction (MMQPCR) in 98 subjects and we conclusively found that SMA cases exhibit telomere attrition compared to healthy controls (P = 4 × 10- 2). Moreover, significant attrition was also observed in severe form of SMA, i.e. SMA type 0 (P = 0.04) as well.Although, the exact mechanism through which telomere shortening contributes to the pathogenesis of SMA is not fully understood and is yet to be delineated. However, one possibility is that telomere shortening leads to genomic instability and DNA damage, which can contribute to motor neuron degeneration. Another possibility is that telomere shortening leads to cellular senescence, which can impair the ability of motor neurons to regenerate and repair themselves. Recent studies have suggested that telomere shortening may be a potential therapeutic target in SMA. Thus, understanding the role of SMN1 gene in disease pathogenesis & its effect on telomere length will aid in estimating the risk & prognosis of SMA in genetically less explored & highly inbred region of Kashmir, Northern India.

Humans↗

PubMed2026

Telomere Length Dynamics as a Biomarker of Individual Radiation Sensitivity and Pneumonitis in Lung Cancer Patients Receiving Thoracic Radiation Therapy.

PURPOSE: Telomere shortening is a biomarker for genome instability and aging, and the vulnerability of telomeric DNA to oxidative damage suggests its potential role in mediating radiation therapy (RT) side effects. This study evaluates telomere length (TL) as a biomarker for clinical radiosensitivity and adverse outcomes in thoracic RT-treated patients. METHODS AND MATERIALS: Patients with cancer receiving thoracic RT (2019-2022) were prospectively enrolled at Brigham and Women's Hospital, Boston, Massachusetts. Peripheral blood mononuclear cells (PBMCs) were collected pre-RT and ≤12 months post-RT. TL was measured using quantitative PCR, and multipathway DNA repair capacity (DRC) was simultaneously assessed by fluorescence multiplex host cell reactivation assays. RT outcomes included patient-reported quality of life and radiation pneumonitis. Linear mixed-effects models were used to analyze TL dynamics; risk prediction models for RT outcomes were evaluated using area under the curve. RESULTS: Pre-RT TL decreased with age (0.44% lower per year; 95% CI, 0.12%-0.77%) and advanced cancer stage (6.87% lower per step increase of stage; 95% CI, 3.45%-10.16%). Radical RT was associated with telomere shortening (3.7% lower; 95% CI, 0.27%-7.07%) in PBMCs, detectable ≤6 months post-RT. Pre-RT TL strongly predicted post-RT changes, and TL dynamics outperformed static measures in predicting symptom burden and radiation pneumonitis. Positive associations were observed between TL and DRC against oxidative lesions, with A:8-oxoG repair capacity mediating 12.8% of RT-induced TL shortening. CONCLUSIONS: Lymphocyte TL can reflect individual radiosensitivity and interact with oxidative damage repair. Longitudinal assessment of TL dynamics provides additional predictive value for adverse RT outcomes compared with static measures. Further studies are needed to fully determine the clinical utility of TL.

Humans↗

PubMed2025

PUMA-induced apoptosis drives bone marrow failure and genomic instability in telomerase-deficient mice.

Bone marrow failure is a severe complication of human telomere biology disorders and predisposes individuals to secondary leukemia. A deeper understanding of this process could offer significant clinical benefits. Using a preclinical mouse model deficient in the RNA component of the telomerase (mTerc), we demonstrate that bone marrow failure results from excessive apoptosis, predominantly mediated by the pro-apoptotic p53 target PUMA. Genetic ablation of Puma alleviates hematological phenotypes and reduces the risk of lethal bone marrow failure while preserving genomic stability. Mechanistically, PUMA deficiency decreases the sensitivity of hematopoietic cells to lethal stressors, including critically short telomeres. As a consequence, reduced compensatory turnover of hematopoietic progenitors slows down telomere shortening at the population level, delays stem cell exhaustion, and diminishes the acquisition of somatic mutations - ultimately preventing neoplastic transformation. Elevated expression of both p53 and PUMA is also observed in the bone marrow from patients with telomere biology disorders. While apoptosis resistance is traditionally associated with malignant transformation, our findings provide evidence that selective inhibition of PUMA-mediated apoptosis may represent a viable therapeutic strategy to prevent or delay leukemic transformation in this patient population.

Animals↗

PubMed2026

Progress on the telomere-telomerase system in planarian neoblasts homeostasis and regeneration.

Planarians are flatworms with remarkable regenerative abilities, and their adult pluripotent stem cells, known as neoblasts, serve as the foundation for this regeneration. Neoblasts can rapidly migrate, proliferate, and undergo directed differentiation following tissue injury to complete regeneration. Telomeres are located at the ends of eukaryotic chromosomes and play a core role in maintaining chromosomal integrity. With each cell division, telomeres shorten. Telomerase is a reverse transcriptase that compensates for telomere loss during cell division by extending telomeric repeats. The telomere-telomerase system is one of the important mechanisms for maintaining stem cell homeostasis. As adult pluripotent stem cells of planarians, neoblasts are required to maintain a dynamic balance between high-frequency cell division and multilineage differentiation. The maintenance of their long-term proliferative capacity and genomic stability may depend on the precise regulation of the telomere-telomerase system. Thus, this system represents a critical entry point for understanding the remarkable regenerative ability of planarians. Integrating recent progress in regeneration, neoblast regulation, and the telomere-telomerase system, we systematically summarize the emerging evidence for telomere- telomerase involvement in neoblast homeostasis and regeneration. We aim to provide insights for research in regenerative medicine, stem cell regulation, and neural injury repair.

Animals↗

PubMed2025

Non-canonical functions of DNMT3A in hematopoietic stem cells regulate telomerase activity and genome integrity.

DNMT3A is a critical regulator of hematopoietic stem cell (HSC) fate decisions and the most recurrently mutated gene in human clonal hematopoiesis (CH). DNMT3A is described as a DNA methyltransferase enzyme, but cells with DNMT3A loss of function show minor changes in DNA methylation that do not correlate with altered gene expression. To explore the possibility that Dnmt3a has DNA-methylation-independent functions in HSCs, we created an allelic series of mice with varying levels of DNA-methylation-impaired Dnmt3a. Clonal expansion of Dnmt3a-deficient HSCs was rescued by Dnmt3a proteins lacking DNA methylation capacity, suggesting that Dnmt3a has important non-canonical functions in HSCs. Dnmt3a-null HSCs can be transplanted indefinitely, implying the ability to circumvent mechanisms that limit the replicative lifespan of HSCs, such as telomere shortening. Dnmt3a-null HSCs show increased telomerase activity and sustain telomere length over serial transplantation, revealing a previously unidentified role for DNMT3A mutations in regulating HSC longevity that is unrelated to DNA methylation function.

Animals↗

PubMed2025

TRB proteins in moss reveal their evolutionarily conserved roles in plant development and telomere maintenance.

Telomere repeat binding (TRB) proteins are plant-specific proteins with a unique domain structure distinct from telomerebinding proteins in animals and yeast. While extensively studied in seed plants, their role in early-diverging plant lineages remains largely unexplored. Here, we investigate TRB proteins in a model moss, Physcomitrium patens, to assess their evolutionary conservation and functional significance. Functional analysis using single knockout mutants revealed that individual PpTRB genes are essential for normal development, with mutants exhibiting defects in the two-dimensional (protonemal) stage, and more prominently, in the formation of three-dimensional (gametophore) structures. Some double mutants displayed telomere shortening, a phenotype also observed in TRB-deficient seed plants, indicating a conserved role for TRBs in telomere maintenance. Transcriptome profiling of TRB mutants revealed altered expression of genes associated with transcriptional regulation and stimulus response in protonema. Subcellular localization studies across various plant cell types confirmed that PpTRBs, like their seed plant counterparts, localize prevalently to the plant nucleus and mutually interact. In bryophytes, TRBs form a monophyletic group that mirrors the species phylogeny, whereas in seed plants, TRBs have diversified into two distinct monophyletic groups. Our findings provide the first comprehensive characterization of TRB proteins in non-vascular plants and demonstrate their conserved roles in telomere maintenance, with additional implications for plant development and gene regulation across land plant lineages.

Bryopsida↗

PubMed2026

Genomic and computational analysis of variants in telomere regulatory genes in subjects with bone marrow failure.

Telomere Biology Disorders (TBDs) are a genetically heterogeneous and often under-recognized cause of Bone Marrow Failure Syndromes (BMFS), driven by defective telomere maintenance and progressive telomere attrition. We performed an integrated genomic, telomeric and computational analysis in 118 subjects presenting clinical features of BMFS to delineate the contribution of Telomere Regulatory Genes (TRGs) variants to disease pathogenesis. Whole exome sequencing (WES) identified pathogenic (18.18%), likely pathogenic (27.27%) and rare variants of uncertain significance (54.54%) in 27 subjects (22.9%) across five TRGs: RTEL1, TERT, TINF2, NOP10, and WRAP53. Telomere Length (TL) assessment revealed significant telomere shortening in TRG variant-positive subjects compared with age-matched controls, with the most profound attrition observed in individuals harboring de novo TINF2 gene variants. RTEL1 emerged as the most frequently affected gene, with recurrent clustering of variants within its C-terminal regulatory region. A familial NOP10 variant, Asp12His, segregated with cutaneous pigmentation and hematological abnormalities consistent with the established role of NOP10 in dyskeratosis congenita, further broadening the known mutational spectrum of the gene. Structure-guided in-silico analyses predicted that both novel and recurrent variants disrupt protein stability, telomerase assembly or trafficking and shelterin complex integrity. Reduced TERT expression and a significant inverse correlation between telomere length and clinical severity further underscored the functional impact of TRG defects. Collectively, this study provides the first comprehensive characterization of TRG variants in the Indian BMFS cohort and highlights the utility of integrating genomic sequencing, telomere length measurement and computational modeling to improve diagnostic precision, variant interpretation and clinical stratification in TBDs.

Journal Article↗

PubMed2026

Occupational exposure to 2,4-dichlorophenoxyacetic acid (2,4-D) and associated oxidative and genomic biomarkers among soybean farmers: a cross-sectional study.

BACKGROUND: 2,4-Dichlorophenoxyacetic acid (2,4-D) is a herbicide widely used for weed control in soybean cultivation. This study aimed to investigate hepatic and genetic damage biomarkers in farmers occupationally exposed to 2,4-D, widely used in soybean cultivation in southern Brazil (Rio Grande do Sul), in addition to estimate urinary 2,4-D concentrations as an indicator of recent exposure. METHODS: A cross-sectional study was conducted, including 54 occupationally exposed farmers and 51 non-exposed controls (organic farmers). RESULTS: Urinary 2,4-D was detected in 88.5% of the exposed group versus 25% of the controls (p < 0.001). Creatine kinase (CK) was significantly elevated in the exposed group (p < 0.05), suggesting possible muscle injury, while AST and ALT (classical liver enzymes) did not differ between groups. Oxidative stress markers showed a clear pattern of redox imbalance, with increased TBARS (p < 0.001), increased CAT activity (p < 0.001), and reduced SOD activity (p < 0.001). Telomere length was significantly shorter in the exposed group (p = 0.001). Use of personal protective equipment (PPE) was reported to be inadequate. CONCLUSION: Occupational exposure to 2,4-D is associated with systemic oxidative stress and telomere shortening, even in the absence of transaminase elevation. This points to early hepatocellular vulnerability mediated by oxidative mechanisms rather than overt cytolysis. The study emphasizes the need for continuous monitoring of populations chronically exposed to chlorophenoxy herbicides.

2,4-dichlorophenoxyacetic acid↗

PubMed2026

Mitotic microhomology-mediated break-induced replication promotes chromoanasynthesis.

Chromoanasynthesis is a form of complex chromosomal rearrangement (CCR) commonly detected in cancers and congenital disorders, but the mechanism underlying its generation remain elusive. Here we develop a single-molecule long-read DNA sequencing approach to characterise ultra-complex mutational events, consistent with chromoanasynthesis, occurring at shortened telomeres and sub-telomeric DNA double-strand breaks in human cells. Our data reveal that chromoanasynthesis is generated by microhomology-mediated break-induced replication (MM-BIR), occurring specifically in mitosis. Surprisingly, this mitotic pathway involves a collaboration between microhomology-mediated end-joining (MMEJ) and BIR, where MMEJ proteins initiate a Polδ-dependent BIR pathway that is regulated by PIF1, POLD3 and PCNA. This pathway is highly prone to template switching and can generate dramatic amplification of genomic loci in a single event. Our findings help explain the extreme mutagenic nature of chromoanasynthesis and establish mitotic MM-BIR as a key driver of CCRs, with important implications for the origin of cancers and congenital disorders.

Humans↗

PubMed2025

Phase separation of hnRNPA1 and TERRA regulates telomeric stability.

Telomeres are the complexes composed of repetitive DNA sequences and associated proteins located at the end of chromatin. As a result of the DNA replication ending issue, telomeric DNA shortens during each cell cycle. The shelterin protein complex caps telomeric ends and forms a high-order protein-DNA structure to protect telomeric DNA. The stability of telomeres is critical for cellular function and related to the progression of many human diseases. Telomeric repeat-containing RNA (TERRA) is a noncoding RNA transcribed from telomeric DNA regions. TERRA plays an essential role in regulating and maintaining the stability of telomeres. Heterogeneous nuclear ribonucleoproteins (hnRNPs) are RNA-binding proteins associated with complex and diverse biological processes. hnRNPA1 can recognize both TERRA and telomeric DNA. Previous research reported that hnRNPA1, TERRA, and POT1, a component of the shelterin complex, work coordinately and displace replication protein A from telomeric single-stranded DNA after DNA replication, promoting telomere capping to preserve genomic integrity. However, the detailed molecular mechanism has remained unclear for >20 years. Here, our study revealed the molecular structure through which the hnRNPA1 UP1 domain interacts with TERRA and identified critical residues on the interacting surface between UP1 and TERRA. Furthermore, we proved that nucleic acids significantly increase the phase-separating ability of hnRNPA1, while disrupting the UP1-TERRA interaction extraordinarily affects hnRNPA1 droplet formation both in vitro and in vivo. Taken together, these data reveal the molecular mechanism of the phase separation of hnRNPA1 and TERRA and the potential contribution of the droplets to maintaining genomic stability.

Heterogeneous Nuclear Ribonucleoprotein A1↗

PubMed2026

Telomere length in patients with non-functional adrenal incidentalomas.

Telomeres maintain genomic integrity during cell replication by preventing chromosomal fusions. Beside genetic influences, telomere length is affected by environmental factors such as oxidative stress and inflammation. These mechanisms also contribute to metabolic syndrome components linked to cellular aging. We aim to evaluate whether telomere length is shortened in patients with non-functional adrenal incidentaloma (NFAI) compared to the control group. This study was designed as a prospective, single-center study. The total of 88 participants included were 44 patients aged between 40 and 60 years with NFAI in our endocrinology clinic and 44 control subjects. An Absolute Human Telomere Lengths Quantification qPCR Assay kit (Nucleotestbio, Budapest, Hungary) was used for analyses. There was no significant difference between the NFAI and control groups regarding age and sex distribution. Telomere length was significantly shorter in the NFAI group (NFAI group: 3.680 ± 1.970 kb; control group: 4.469 ± 1.672 kb; p = 0.046). While no significant difference was found in telomere lengths in subgroup analyses, patients with basal adrenocorticotropic hormone (ACTH) levels <15 pg/mL had significantly shorter telomeres than those with basal ACTH levels ≥15 pg/mL (p = 0.034). A strong positive correlation was observed only between telomere length and ACTH level (p = 0.001). This study demonstrated that telomere length is significantly shortened in NFAI patients. Here, we propose that the underlying cause of telomere length shortening in the NFAI group may be related to increased cardiovascular risk and an elevated inflammatory state, even in the presence of cortisol levels within the normal range.

Humans↗

PubMed2025

Subtelomeric elements provide stability to short telomeres in telomerase-negative cells of the budding yeast Naumovozyma castellii.

Telomerase plays an important role in sustaining eukaryotic linear chromosomes, as elongation of telomeres is needed to counterbalance the shortening occurring in each replication round. Nevertheless, in telomerase-deficient cells, Alternative Lengthening of Telomeres (ALT) pathways can maintain telomeres by employing recombination-based mechanisms. In the budding yeast Naumovozyma castellii, effective activation of the ALT pathway leads to bypass of senescence and supports long-term growth. We found that telomere structures in N. castellii ALT cells are stably maintained at a shortened uniform length over extensive numbers of generations. This is correlated to the spreading of a subtelomeric sequence, TelKO element, to all telomeres. Genome sequencing of the wild-type strain revealed variants of the TelKO element, differing in their lengths, and separate ALT strains are maintained by spreading of distinct TelKO element variants. Although short uniform telomere structures are predominant, sporadic telomere lengthening events occur by addition of long repeated arrays of TelKO elements. The telomere-binding protein Rap1 can bind to TelKO sequences in vitro, indicating a functional role of TelKO elements in providing stability to shortened ALT telomeres. Our results suggest that stable maintenance and telomere functionality may be achieved by incorporating the distal subtelomeric TelKO sequences into the telomeric chromatin cap.

Telomerase↗

PubMed2024

Effects of particulate air pollution on BPDE-DNA adducts, telomere length, and mitochondrial DNA copy number in human exhaled breath condensate and BEAS-2B cells.

Traffic-related particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) have been linked to respiratory diseases and cancer risk in humans. Genomic damage, including benzo[a]pyrene diolepoxide (BPDE)-DNA adducts as well as alterations in telomere length (TL) and mitochondrial DNA copy number (mtDNA-CN) are associated with respiratory diseases. This study aimed to investigate the association between exposure to traffic-related particulate pollutants and genomic damage in exhaled breath condensate (EBC) in human subjects and a bronchial epithelial cell line (BEAS-2B). Among the 60 healthy recruited subjects, residents living in high-traffic-congested areas were exposed to higher concentrations of PM2.5 (1.66-fold, p < 0.01), UFPs (1.79-fold, p < 0.01), PM2.5-PAHs (1.50-fold, p < 0.01), and UFPs-PAHs (1.35-fold, p < 0.05), than those in low-traffic-congested areas. In line with increased exposure to particulate air pollution, the high-traffic-exposed group had significantly increased BPDE-DNA adducts (1.40-fold, p < 0.05), TL shortening (1.24-fold, p < 0.05), and lower mtDNA-CN (1.38-fold, p < 0.05) in EBC. The observations in the human study linking exposure to PM2.5, UFPs, PM2.5-PAHs, and UFPs-PAHs with the aforementioned biological effects were confirmed by an in vitro cell-based study, in which BEAS-2B cells were treated with diesel exhaust particulate matter (DEP) containing fine and ultrafine PM and PAHs. Increased BPDE-DNA adducts levels, shortened TL, and decreased mtDNA-CN were also found in treated BEAS-2B cells. The shortened TL and decreased mtDNA-CN were in part mediated by decreased transcript levels of hTERT, and SIRT1, which are involved in telomerase activity and mitochondrial biogenesis, respectively. These results suggest that exposure to traffic-related particulate pollutants can cause genomic instability in respiratory cells, which may increase the health risk of respiratory diseases and the development of cancer.

Humans↗