Genetics of human telomere biology disorders

Comparing telomere lengths in chondrocytes from intact cartilage and those isolated from loose bodies

INTRODUCTION

Given the intrinsic connection between telomeres, cell replication, and aging, telomere length serves as a valuable biomarker for evaluating cell quality and viability. Studying telomeres can offer vital insights into the suitability of cells within articular loose bodies for autologous chondrocyte implantation in treating chondral lesions. The aim of this study was to assess cell quality by analyzing telomere profiles in isolated cells from loose bodies.

METHODS

Chondrocytes from loose bodies and intact cartilage from 3 patients with osteochondritis dissecans who underwent a High Density-Autologous Chondrocyte Implantation (HD-ACI), were isolated and cultured. Telomere length was determined by High-Throughput Quantitative Fluorescence in situ Hybridization (HT-Q-FISH). Percentile of telomere length, percentages of telomere length values (QuantiTel), percentages of cells with specific telomere values (QuantiCell) were estimated in each sample.

RESULTS

Percentile and QuantiTel showed lower telomere lengths in chondrocytes from loose bodies than in those from intact cartilage. QuantiCell demonstrated that the percentage of cells with shorter telomeres was higher in cells from loose bodies than in intact cartilage. Median telomere length was statistically higher in chondrocytes from intact biopsies than in loose bodies.

CONCLUSION

Chondrocytes isolated from loose bodies exhibits a telomere distribution shorter than those from intact cartilage.

Late-onset telomere biology disorders in adults: clinical insights and treatment outcomes from a retrospective registry cohort

ABSTRACT

Pathogenic germ line variants affecting proper telomere maintenance result in premature telomere shortening and cause telomere biology disorders (TBDs). Although classical dyskeratosis congenita in children is rather well defined, late-onset ("cryptic") TBDs remain underrecognized, resulting in underdiagnosis and inadequate treatment in affected adults. Here, we present a series of adult TBD cases collected through the German TBD reference center between 2014 and 2024. Patients aged ≥18 years with an age-matched telomere length (TL) <10th percentile in lymphocytes, a detection of either a variant of uncertain significance, a pathogenic, or a likely pathogenic variant in TBD-associated genes, and available clinical data were included in this analysis. Based on this, a novel point-based algorithm for categorization into proven, probable, and suspected-only TBD cases was developed. Of 1537 TL analyses, 42 patients with proven (n = 29) or probable (n = 13) TBD were identified. The median age at first clinical manifestation and at diagnosis was 20.0 and 34.1 years, respectively. Bone marrow failure (BMF) was the most frequent manifestation observed in our cohort (73.8%), followed by liver or interstitial lung diseases (50.0% and 41.5%, respectively). Immunosuppressive therapy was administered in 6 patients with BMF, but none of them responded. In comparison, 8 of 8 evaluable patients treated with androgen derivatives showed hematologic response. Our data provide novel real-world insights into the clinical manifestation spectrum, diagnosis, clinical course, and treatment of TBD in adult, late-onset cases of this hereditary disease.

Telomeres and Telomerase: Targets for Chemoprevention of Hepatocellular Carcinoma With Bioactive Food Compounds

The maintenance of telomere length by telomerase plays an essential role in senescence, aging, and cancer. Mutations in the TERT promoter, a telomerase subunit, are frequent in human cancers. In hepatocellular carcinoma (HCC), telomere shortening contributes to preneoplastic conditions such as cirrhosis. Telomerase activation during cirrhosis may reduce chromosomal instability, while its suppression in early dysplastic nodules may prevent hepatocarcinogenesis. Evidence suggests that bioactive food compounds (BFCs) can reduce the incidence and/or delay the onset of HCC by modulating telomerase activity. A systematic review was conducted on the role of BFCs in telomerase activity during hepatocarcinogenesis. BFCs were analyzed in isolated form or as part of extracts and categorized into fatty acids, isoprenoids, isothiocyanates, and phenolic compounds. Despite structural diversity, BFCs modulate telomerase through common mechanisms, including inhibition of activating proteins at the TERT promoter, activation of nuclear receptors, or histone H3 hyperacetylation. Indirectly, telomerase can also be modulated via activation of antioxidant defense pathways. Understanding telomerase reactivation and its modulation by BFCs is key to establishing effective HCC chemoprevention strategies targeting telomerase.

Clinical impact of donor telomere length after umbilical cord blood transplantation

BACKGROUND AND AIMS

Several studies have shown that the telomere length of engrafted donor cells affects the clinical outcomes in patients with hematologic diseases after allogeneic stem-cell transplantation (allo-SCT). However, the relationship between donor telomere length and clinical outcomes after umbilical-cord blood transplantation (UCBT) remains unknown. The study aim was to assess the relationship between donor telomere length and transplantation outcomes.

METHODS

We measured donor-derived relative telomere length (RTL) in 75 patients after single-unit UCBT and evaluated the association between telomere length and transplantation outcomes.

RESULTS

Compared with patients with shorter RTL, patients with longer RTL had a higher risk of bacterial and bloodstream infections [hazard ratio (HR), 4.79; 95% confidence interval (CI), 1.70-13.46; P = 0.003 and HR, 3.43; 95% CI, 1.19-9.82; P = 0.022, respectively] and was possibly associated with reduced relapse (HR 0.44, 95% CI 0.15-1.27, P = 0.13) by multivariate analysis.

CONCLUSIONS

Patients after UCBT who received engrafted donor cells with longer RTL had a higher risk of bacterial and bloodstream infections. The measured donor-derived RTL at engraftment after UCBT may predict clinical outcomes.

Identification of biallelic POLA2 variants in two families with an autosomal recessive telomere biology disorder

POLA2 encodes the accessory subunit of DNA polymerase α (polα)/primase, which is crucial for telomere C-strand fill-in. Incomplete fill-in of the C-rich telomeric strand after DNA replication has been proposed as a mechanism for Coats plus syndrome, a phenotype within the broader spectrum of telomere biology disorders (TBD). Coats plus syndrome has so far been associated with pathogenic variants in POT1, CTC1, and STN1. Here we report the findings of biallelic deleterious rare variants in POLA2 gene detected by whole genome sequencing and segregation analysis in five young adults from two unrelated families. All five individuals displayed abnormally short telomeres and a clinical phenotype suggesting a TBD disorder with Coats plus features including retinal and gastrointestinal telangiectasias. Our results suggest POLA2 as a novel autosomal recessive gene for a TBD with Coats plus features.

Shorter Telomeres and Faster Telomere Attrition in Individuals With Five Syndromic Forms of Intellectual Disability: A Systematic Review and Meta-Analysis

BACKGROUND

People with intellectual disability suffer complex challenges due to adaptive functioning limitations, high rates of chronic diseases and shortened lifespans compared with the general population. Telomere shortening is a hallmark of ageing, and short telomeres are linked to neurological disorders. The main objective of this systematic review and meta-analysis was to identify any differences in telomere length and the rate of telomere attrition in leukocytes and fibroblasts from people with intellectual disability and controls.

METHODS

PubMed, Scopus and ScienceDirect were searched. Articles that compared telomere length in individuals with intellectual disability to apparently healthy age-matched controls were included. Risk of bias was assessed using the AXIS tool and data were analysed using CMA.

RESULTS

Fifteen studies comprised of 17 comparisons provided data and were included in meta-analyses. Compared with healthy controls (N = 481), people with intellectual disability (N = 366) from a known genetic syndrome (Cri du chat, Down, Hoyeraal-Hreidarsson, Williams or Nicolaides-Baraitser) possessed shorter leukocyte telomeres (SMD: -0.853 [95% CI: -1.622 to -0.084], p = 0.03). Similarly, relative to controls (N = 16), people with syndromic intellectual disability (N = 21) possessed shorter fibroblast telomeres (-1.389 [-2.179 to -0.599], p = 0.001). Furthermore, people with syndromic forms of intellectual disability also demonstrated a faster rate (2.09-fold) of telomere shortening.

CONCLUSIONS

Consistent with epidemiological findings on mortality and morbidity risk, people with syndromic intellectual disability appear to undergo a faster rate of biological ageing compared to the general population. These findings emphasise the need for healthy ageing lifestyle (i.e., exercise and stress management) and therapeutic interventions for people with syndromic intellectual disability.

From severe aplastic anemia with TERT variant to Wilson disease - associations or not

Severe aplastic anemia is a life-threatening ineffective hematopoiesis, arising from inherited or acquired traits. Wilson disease is a rare congenital metabolic disorder with copper accumulation. Here we report a rare case of a 15-year-old boy, who presented with bone marrow failure. Whole exome sequencing revealed several gene mutations in ATP7B and TERT. Based on the phenotypes, telomere lengths and pedigree of his family, the patient was diagnosed with severe aplastic anemia accompanied by Wilson disease. Allogeneic hematopoietic stem cell transplantation and anti-copper therapy helped him achieve transfusion independence and restore relatively normal copper metabolism. We discussed the possible associations between the two rare conditions and optimal management in this situation.

ATM-dependent DNA damage response constrains cell growth and drives clonal hematopoiesis in telomere biology disorders

Telomere biology disorders (TBDs) are genetic diseases caused by defective telomere maintenance. TBD patients often develop bone marrow failure and have an increased risk of myeloid neoplasms. To better understand the factors underlying hematopoietic outcomes in TBD, we comprehensively evaluated acquired genetic alterations in hematopoietic cells from 166 pediatric and adult TBD patients. Of these patients, 47.6% (28.8% of children, 56.1% of adults) had clonal hematopoiesis. Recurrent somatic alterations involved telomere maintenance genes (7.6%), spliceosome genes (10.4%, mainly U2AF1 p.S34), and chromosomal alterations (20.2%), including 1q gain (5.9%). Somatic variants affecting the DNA damage response (DDR) were identified in 21.5% of patients, including 20 presumed loss-of-function variants in ataxia-telangiectasia mutated (ATM). Using multimodal approaches, including single-cell sequencing, assays of ATM activation, telomere dysfunction-induced foci analysis, and cell-growth assays, we demonstrate telomere dysfunction-induced activation of the ATM-dependent DDR pathway with increased senescence and apoptosis in TBD patient cells. Pharmacologic ATM inhibition, modeling the effects of somatic ATM variants, selectively improved TBD cell fitness by allowing cells to bypass DDR-mediated senescence without detectably inducing chromosomal instability. Our results indicate that ATM-dependent DDR induced by telomere dysfunction is a key contributor to TBD pathogenesis and suggest dampening hyperactive ATM-dependent DDR as a potential therapeutic intervention.

Leukocyte telomere attrition in cognitive decline: associations with APOE genotype and cardiovascular risk factors

Telomere shortening represents a fundamental mechanism of cellular aging potentially implicated in neurodegenerative processes. This study investigated the complex associations among leukocyte telomere length, cardiovascular risk profiles, and APOE polymorphisms in age-related cognitive decline. Through a cross-sectional analysis of 90 participants stratified by cognitive status into three groups: cognitively unimpaired (CU), mild cognitive impairment (MCI), and Alzheimer's Disease (AD), we quantified relative telomere length using quantitative PCR, performed APOE genotyping and assessed cardiovascular risk factors. Quantitative analysis revealed significantly reduced telomere length in the AD group compared to CU and MCI groups. Multivariate regression analysis identified cognitive status as an independent predictor of telomere length (β = -0.468, p < 0.001). APOE ε4 carrier status showed higher prevalence in AD subjects as expected. Cardiovascular risk factors demonstrated no significant correlation with telomere length across cognitive groups. Our findings establish a robust association between telomere shortening and advanced cognitive impairment in AD, suggesting potential utility as a neurodegenerative biomarker. This relationship appears independent of traditional cardiovascular risk factors, highlighting the complexity of cellular aging mechanisms in neurodegeneration.

Loss of Ten1 in mice induces telomere shortening and models human dyskeratosis congenita

Telomere length regulation is essential for genome stability as short telomeres can trigger cellular senescence and apoptosis constituting an integral aspect of biological aging. Telomere biology disorders (TBDs) such as dyskeratosis congenita (DC) are rare, inherited diseases with known mutations in at least 16 different genes encoding components of the telomere maintenance complexes. The precise role of TEN1, part of the CST complex (CTC1, STN1, and TEN1), and the consequences of its loss of function in vivo are not yet known. We investigated the first viable murine model of Ten1 deficiency created by CRISPR-Cas9-mediated exon 3 deletion. Ten1 homozygous knockout mice present with telomere attrition, short life span, skin hyperpigmentation, aplastic anemia, and cerebellar hypoplasia. Molecular analyses revealed a reduction of proliferating cells, increased apoptosis, and stem cell depletion with activation of the p53/p21 signaling pathway. Our data demonstrate that Ten1 deficiency causes telomere shortening and associates with accelerated aging.

Protection of the genome and the central exome by peripheral non-coding DNA against DNA damage in health, ageing and age-related diseases

DNA in eukaryotic genomes is under constant assault from both exogenous and endogenous sources, leading to DNA damage, which is considered a major molecular driver of ageing. Fortunately, the genome and the central exome are safeguarded against these attacks by abundant peripheral non-coding DNA. Non-coding DNA codes for small non-coding RNAs that inactivate foreign nucleic acids in the cytoplasm and physically blocks these attacks in the nucleus. Damage to non-coding DNA produced during such blockage is removed in the form of extrachromosomal circular DNA (eccDNA) through nucleic pore complexes. Consequently, non-coding DNA serves as a line of defence for the exome against DNA damage. The total amount of non-coding DNA/heterochromatin declines with age, resulting in a decrease in both physical blockage and eccDNA exclusion, and thus an increase in the accumulation of DNA damage in the nucleus during ageing and in age-related diseases. Here, we summarize recent evidence supporting a protective role of non-coding DNA in healthy and pathological states and argue that DNA damage is the proximate cause of ageing and age-related genetic diseases. Strategies aimed at strengthening the protective role of non-coding DNA/heterochromatin could potentially offer better systematic protection for the dynamic genome and the exome against diverse assaults, reduce the burden of DNA damage to the exome, and thus slow ageing, counteract age-related genetic diseases and promote a healthier life for individuals.

Association of metallic elements with telomere length in children with autism spectrum disorder

Background

Imbalances in metal elements have been identified as a potential risk factor for autism spectrum disorder (ASD), and shortened telomere length (TL) is commonly observed in children with ASD. Metal elements may influence telomere homeostasis through oxidative stress, which could contribute to the pathogenesis of autism. However, studies examining the combined effects of metal elements on TL in children with ASD are limited. To fill the gaps in the current literature, this study aimed to investigate the relationship between six metallic elements: manganese (Mn), copper (Cu), zinc (Zn), calcium (Ca), magnesium (Mg), and iron (Fe), and TL in the whole blood of children with ASD.

Methods

A total of 83 children with ASD and 95 typically developing children were recruited. TL was measured using digital PCR, while metal concentrations were assessed using inductively coupled plasma mass spectrometry (ICP-MS). Linear regression analysis was first conducted to explore the correlations between metal elements and TL in both groups. Additionally, Bayesian Kernel Machine Regression (BKMR) was used to further examine the combined effects and potential interactions of these metals on TL in the ASD group.

Results

In the ASD group, Ca was found to have a protective effect on TL (β = 0.07, 95% CI [0.01-0.13], P = 0.027). In contrast, Mg showed a protective effect on TL in the control group (β = 0.10, 95% CI [0.01-0.18], P = 0.027). The BKMR model revealed a significant positive combined effect of the metal mixtures on TL in the ASD group, with Ca having the largest individual effect (PIP = 0.45). Further analysis indicated that increases in Zn and Mn concentrations from the 25th to the 75th percentile were negatively correlated with TL, while higher concentrations of Cu, Ca, Mg, and Fe were positively associated with TL. No significant interactions among the metals were observed.

Conclusions

This study suggests a potential link between metallic elements and TL in children with ASD, with Ca having the greatest effect. Our findings highlight the potential benefits of appropriate calcium supplementation as a protective strategy for lengthening telomeres in children with ASD, emphasizing the importance of early nutritional interventions to improve their overall health.

Telomere function and regulation from mouse models to human ageing and disease

Telomeres protect the ends of chromosomes but shorten following cell division in the absence of telomerase activity. When telomeres become critically short or damaged, a DNA damage response is activated. Telomeres then become dysfunctional and trigger cellular senescence or death. Telomere shortening occurs with ageing and may contribute to associated maladies such as infertility, neurodegeneration, cancer, lung dysfunction and haematopoiesis disorders. Telomere dysfunction (sometimes without shortening) is associated with various diseases, known as telomere biology disorders (also known as telomeropathies). Telomere biology disorders include dyskeratosis congenita, Høyeraal-Hreidarsson syndrome, Coats plus syndrome and Revesz syndrome. Although mouse models have been invaluable in advancing telomere research, full recapitulation of human telomere-related diseases in mice has been challenging, owing to key differences between the species. In this Review, we discuss telomere protection, maintenance and damage. We highlight the differences between human and mouse telomere biology that may contribute to discrepancies between human diseases and mouse models. Finally, we discuss recent efforts to generate new 'humanized' mouse models to better model human telomere biology. A better understanding of the limitations of mouse telomere models will pave the road for more human-like models and further our understanding of telomere biology disorders, which will contribute towards the development of new therapies.

Exploring the Mechanisms of Testicular Aging: Advances in Biomarker Research

Aging biomarkers quantify aging progression and provide actionable targets for therapeutic interventions to mitigate age-related decline. This review synthesizes emerging evidence on testicular aging biomarkers, focusing on cellular senescence (Leydig, Sertoli, and endothelial cells), protein homeostasis disruption, mitochondrial dysfunction, germ stem cell depletion, sperm telomere length, epigenetic alterations, oxidative stress, inflammation, and gut microbiota dysbiosis. We propose that testicular aging serves as a critical nexus linking reproductive decline with systemic aging processes, with its pathological progression being quantifiable through specific biomarkers including the Leydig, Sertoli, and endothelial cells, INSL3, ribosomal protein RPL39L, sperm telomere length, relative telomere length mitochondrial translocator protein, and sialic acid. By bridging systemic aging paradigms with testis-specific mechanisms, we emphasize the urgency to identify organ-selective biomarkers for targeted interventions, advancing strategies to preserve male fertility and address population aging challenges.

Azacitidine and venetoclax for the treatment of AML arising from an underlying telomere biology disorder

Telomere biology disorders (TBDs) are a group of genetic conditions characterized by defects in telomere maintenance leading to multisystemic organ involvement and a predisposition to hematologic malignancies. The management of patients with TBDs who develop acute myeloid leukemia (AML) presents a significant challenge due to their limited bone marrow reserve and non-hematopoietic organ dysfunction. We present the case of a 45-year-old patient with a previously unrecognized TBD who presented with AML. The patient's history of longstanding cytopenias, idiopathic avascular necrosis, and pulmonary fibrosis were suggestive of a TBD, which was confirmed through telomere length testing and the presence of a TERT variant. Due to his underlying TBD, he was treated with dose-reduced azacitidine and venetoclax, adapting the approach commonly employed in elderly, co-morbid AML patients ineligible for intensive chemotherapy. This resulted in a complete remission with incomplete count recovery that has persisted for greater than 12 months to date. Aside from prolonged myelosuppression, the patient tolerated the regimen well with minimal toxicity. To our knowledge, this is the first report of the successful utilization of azacitidine and venetoclax as an AML treatment modality in TBD patients and underscores the potential of this regimen as an effective non-intensive treatment strategy for high grade myeloid neoplasms arising in the context of inherited bone marrow failure syndromes.

Oxidative events in a double helix system promote the formation of kinetically trapped G-quadruplexes

Guanine-rich oligonucleotide sequences can adopt four-stranded G-quadruplex structures. These sequences are highly susceptible to oxidative damage due to the low redox potential of their constituent guanine nucleotides. Oxidative lesions of guanine residue exhibit perturbations in the position of hydrogen-bond donors and acceptors, which can impair the formation of G-quadruplexes. Here we studied the effect of guanine oxidation in model systems comprised of a G-rich as well as a complementary C-rich DNA strand to discern how oxidative damage can destabilize double-stranded DNA and promote G-quadruplex formation. Our data show that G-rich strands containing oxidative lesions can still adopt the G-quadruplex fold due to the presence of spare G-tracts, which rescue the damaged G-tracts via either full or partial replacement. However, most of the observed G-quadruplexes are kinetically trapped structures and the preferred equilibrium state of the two-stranded constructs is double-stranded DNA.

Telomere length in offspring is determined by mitochondrial-nuclear communication at fertilization

The initial setting of telomere length during early life in each individual has a major influence on lifetime risk of aging-associated diseases; however there is limited knowledge of biological signals that regulate inheritance of telomere length, and whether it is modifiable is not known. We now show that when mitochondrial activity is disrupted in mouse zygotes, via exposure to 20% O2 or rotenone, telomere elongation between the 8-cell and blastocyst stage is impaired, with shorter telomeres apparent in the pluripotent Inner Cell Mass (ICM) and persisting after organogenesis. Identical defects of elevated mtROS in zygotes followed by impaired telomere elongation, occurred with maternal obesity or advanced age. We further demonstrate that telomere elongation during ICM formation is controlled by mitochondrial-nuclear communication at fertilization. Using mitochondrially-targeted therapeutics (BGP-15, MitoQ, SS-31, metformin) we demonstrate that it is possible to modulate the preimplantation telomere resetting process and restore deficiencies in neonatal telomere length.

Redox regulation: mechanisms, biology and therapeutic targets in diseases

Redox signaling acts as a critical mediator in the dynamic interactions between organisms and their external environment, profoundly influencing both the onset and progression of various diseases. Under physiological conditions, oxidative free radicals generated by the mitochondrial oxidative respiratory chain, endoplasmic reticulum, and NADPH oxidases can be effectively neutralized by NRF2-mediated antioxidant responses. These responses elevate the synthesis of superoxide dismutase (SOD), catalase, as well as key molecules like nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione (GSH), thereby maintaining cellular redox homeostasis. Disruption of this finely tuned equilibrium is closely linked to the pathogenesis of a wide range of diseases. Recent advances have broadened our understanding of the molecular mechanisms underpinning this dysregulation, highlighting the pivotal roles of genomic instability, epigenetic modifications, protein degradation, and metabolic reprogramming. These findings provide a foundation for exploring redox regulation as a mechanistic basis for improving therapeutic strategies. While antioxidant-based therapies have shown early promise in conditions where oxidative stress plays a primary pathological role, their efficacy in diseases characterized by complex, multifactorial etiologies remains controversial. A deeper, context-specific understanding of redox signaling, particularly the roles of redox-sensitive proteins, is critical for designing targeted therapies aimed at re-establishing redox balance. Emerging small molecule inhibitors that target specific cysteine residues in redox-sensitive proteins have demonstrated promising preclinical outcomes, setting the stage for forthcoming clinical trials. In this review, we summarize our current understanding of the intricate relationship between oxidative stress and disease pathogenesis and also discuss how these insights can be leveraged to optimize therapeutic strategies in clinical practice.

Inducible pluripotent stem cell models to study bone marrow failure and MDS predisposition syndromes

Induced pluripotent stem cells (iPSCs) have emerged as powerful tools for in vitro modeling of bone marrow failure (BMF) syndromes and hereditary conditions predisposing to myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). This review synthesizes recent advances in iPSC-based disease modeling for various inherited BMF/MDS disorders, including Fanconi anemia, dyskeratosis congenita, Diamond Blackfan anemia syndrome, Shwachman-Diamond syndrome, and severe congenital neutropenia as well as GATA2, RUNX1, ETV6, ANKRD26, SAMD9, SAMD9L, and ADH5/ALDH2 syndromes. Although the majority of these iPSC lines are derived from patient cells, some are generated by introducing patient-specific mutations into healthy iPSC backgrounds, offering complementary approaches to disease modeling. The review highlights the ability of iPSCs to recapitulate key disease phenotypes, such as impaired hematopoietic differentiation, telomere dysfunction, and defects in DNA repair or ribosome biogenesis. We discuss how these models have enhanced our understanding of disease pathomechanisms, hematopoietic defects, and potential therapeutic approaches. Challenges in generating and maintaining disease-specific iPSCs are examined, particularly for disorders involving DNA repair. We emphasize the necessity of creating isogenic controls to elucidate genotype-phenotype relationships. Furthermore, we address limitations of current iPSC models, including genetic variability among iPSC clones derived from the same patient, and difficulties in achieving robust engraftment of iPSC-derived hematopoietic progenitor cells in mouse transplantation models. The review also explores future directions, including the potential of iPSC models for drug discovery and personalized medicine approaches. This review underscores the significance of iPSC technology in advancing our understanding of inherited hematopoietic disorders and its potential to inform novel therapeutic strategies.

Human telomere length detected by quantitative fluorescent in situ hybridization: overlooked importance and application

The technique of Quantitative Fluorescence in Situ Hybridization (Q-FISH) plays a crucial role in determining the length of telomeres for studies in molecular biology and cytogenetics. Throughout the years, the use of Q-FISH for measuring telomere length has made substantial contributions to research in aging, cancer, and stem cells. The objective of this analysis is to delineate the categorization, fundamental concepts, pros and cons, and safety measures of Q-FISH in telomere length analysis, encapsulate, and anticipate its principal uses across diverse human biomedical research fields.

Clinical Use of ZSCAN4 for Telomere Elongation in Hematopoietic Stem Cells

BACKGROUND

Extremely short telomeres in patients with dyskeratosis congenita and related telomere biology disorders (TBDs) lead to premature cellular senescence and bone marrow failure. Zinc finger and SCAN domain-containing 4 (ZSCAN4) elongates telomeres by recombination.

METHODS

We report a clinical study in which EXG34217, the term given for autologous CD34+ hematopoietic stem cells from patients with TBD exposed to a temperature-sensitive Sendai virus vector encoding human ZSCAN4 at 33°C for 24 hours, was infused into patients without preconditioning.

RESULTS

Four patients were enrolled; two experienced successful CD34+ mobilization during the second mobilization attempt and underwent apheresis and EXG34217 infusion, with follow-up of 5 and 24 months (both ongoing). We observed telomere elongation (1.06- to 1.34-fold) in CD34+ cells ex vivo. In one patient, the treatment was associated with a change in the mean absolute neutrophil count (ANC) from 1.78×103 to 3.18×103 cells/μl; the lymphocyte subpopulation telomere length changed from 3.6 to 6.7 kb (50th percentile for age). In the other patient, the treatment was associated with a change in the lowest ANC from 0.6×103/μl to 1.2×103/μl; this has occurred in 5 months without the patient receiving prior intermittent low-dose granulocyte-colony-stimulating factor injections. During mobilization, all patients experienced mild to moderate bone pain or pain after line replacement, and one patient had a blood infection associated with fever and hypoxemia. After EXG34217 infusion, no acute safety issues were noted; in one patient mild to moderate long-term cardiac and pulmonary adverse events were noted; these were similar to symptoms of the patient's underlying conditions.

CONCLUSIONS

Although definitive conclusions cannot be drawn from the two EXG34217-treated patients, these results warrant further investigation of CD34+ cells exposed to ZSCAN4 for treating TBDs. (Funded by Elixirgen Therapeutics; ClinicalTrials.gov number, NCT04211714.).

Rapid dynamics allow the low-abundance RTEL1 helicase to promote telomere replication

Regulator of telomere length 1 (RTEL1) helicase facilitates telomere replication by disassembling DNA secondary structures, such as G-quadruplexes and telomeric loops (t-loops), at the ends of the chromosomes. The recruitment of RTEL1 to telomeres occurs during the S-phase of the cell cycle, but the dynamics of the process has not been studied. Here, we utilized CRISPR genome editing and single-molecule imaging to monitor RTEL1 movement within human cell nuclei. RTEL1 utilizes rapid three-dimensional diffusion to search for telomeres and other nuclear targets. Only 5% of the chromatin-bound RTEL1 is associated with telomeres at any time in the S-phase, but the telomere-bound RTEL1 has much more extended associations. This binding is enhanced by the interaction between RTEL1 and the telomeric protein TRF2 but is largely independent of RTEL1 ATPase activity. The absence of RTEL1 catalytic activity leads to severe defects in cell proliferation, slow progression out of S-phase, and chromosome end-to-end fusion events. We propose that the rapid diffusion of RTEL1 allows this low-abundance protein to explore the nucleus, bind TRF2, and be recruited to telomeres.

Telomeropathies in Interstitial Lung Disease and Lung Transplant Recipients

Telomeropathies, or telomere biology disorders (TBDs), are syndromes that can cause a number of medical conditions, including interstitial lung disease (ILD), bone marrow failure, liver fibrosis, and other diseases. They occur due to genetic mutations to the telomerase complex enzymes that result in premature shortening of telomeres, the caps on the ends of cellular DNA that protect chromosome length during cell division, leading to early cell senescence and death. Idiopathic pulmonary fibrosis (IPF) is the most common manifestation of the telomere biology disorders, although it has been described in other interstitial lung diseases as well, such as rheumatoid arthritis-associated ILD and chronic hypersensitivity pneumonitis. Telomere-related mutations can be inherited or can occur sporadically. Identifying these patients and offering genetic counseling is important because telomerapathies have been associated with poorer outcomes including death, lung transplantation, hospitalization, and FVC decline. Additionally, treatment with immunosuppressants has been shown to be associated with worse outcomes. Currently, there is no specific treatment for TBD except to transplant the organ that is failing, although there are a number of promising treatment strategies currently under investigation. Shortened telomere length is routinely discovered in patients undergoing lung transplantation for IPF. Testing to detect early TBD in patients with suggestive signs or symptoms can allow for more comprehensive treatment and multidisciplinary care pre- and post-transplant. Patients with TBD undergoing lung transplantation have been reported to have both pulmonary and extrapulmonary complications at a higher frequency than other lung transplant recipients, such as graft-specific complications, increased infections, and complications related to immunosuppressive therapy.

Extracellular vesicles in tumor immunity: mechanisms and novel insights

Extracellular vesicles (EVs), nanoscale vesicles secreted by cells, have attracted considerable attention in recent years due to their role in tumor immunomodulation. These vesicles facilitate intercellular communication by transporting proteins, nucleic acids, and other biologically active substances, and they exhibit a dual role in tumor development and immune evasion mechanisms. Specifically, EVs can assist tumor cells in evading immune surveillance and attack by impairing immune cell function or modulating immunosuppressive pathways, thereby promoting tumor progression and metastasis. Conversely, they can also transport and release immunomodulatory factors that stimulate the activation and regulation of the immune system, enhancing the body's capacity to combat malignant diseases. This dual functionality of EVs presents promising avenues and targets for tumor immunotherapy. By examining the biological characteristics of EVs and their influence on tumor immunity, novel therapeutic strategies can be developed to improve the efficacy and relevance of cancer treatment. This review delineates the complex role of EVs in tumor immunomodulation and explores their potential implications for cancer therapeutic approaches, aiming to establish a theoretical foundation and provide practical insights for the advancement of future EVs-based cancer immunotherapy strategies.

A novel TERT variant associated with a telomere biology disorder and challenges in variant classification

Telomere biology disorders (TBDs) are inherited conditions associated with multisystem manifestations. We describe clinical and functional characterisation of a novel TERT variant. Whole-genome sequencing was performed along with single telomere length analysis (STELA). Telomerase activity and processivity were assessed. A novel TERT variant (K710R) was detected in a patient with classic TBD features showing reduced telomerase activity and processivity. Despite clinical and functional evidence, the variant was classified as a variant of uncertain significance. We have described a novel TERT variant and highlighted the need for further refinement of variant classification specific for TBDs.

Older Age as a Worrisome Feature in Patients With Intraductal Papillary Mucinous Neoplasms: A Long-Term Surveillance Study

INTRODUCTION

Aging has been implicated in the development of various cancer types. No study has specifically investigated age at intraductal papillary mucinous neoplasm (IPMN) diagnosis in relation to the long-term risk of pancreatic carcinogenesis.

METHODS

Within a prospective cohort of 4,104 patients diagnosed with pancreatic cysts, we identified 3,142 patients with IPMNs and examined an association of age at IPMN diagnosis with the incidence of pancreatic carcinoma. Using the multivariable competing-risks proportional hazards regression model, we estimated subdistribution hazard ratios (SHRs) and 95% confidence intervals (CIs) for pancreatic carcinoma incidence according to age at IPMN diagnosis.

RESULTS

During 22,187 person-years of follow-up, we documented 130 patients diagnosed with pancreatic carcinoma (64 with IPMN-derived carcinoma and 66 with concomitant ductal adenocarcinoma). Older age at IPMN diagnosis was associated with a higher risk of pancreatic cancer incidence ( Ptrend = 0.002). Compared with patients younger than 55 years, patients aged 55-64, 65-74, and ≥ 75 years had adjusted SHRs of 1.80 (95% CI, 0.75-4.32), 2.56 (95% CI, 1.10-5.98), and 3.31 (95% CI, 1.40-7.83), respectively. Patients aged 70 years and older had a numerically similar adjusted SHR compared with patients younger than 70 years with worrisome features defined by the international consensus guidelines (1.73 [95% CI, 1.01-2.97] and 1.66 [95% CI, 0.89-3.10], respectively).

DISCUSSION

Older patients with IPMNs were at a higher risk of developing pancreatic carcinoma during surveillance. Surgically fit elderly patients may be good candidates for periodic surveillance aimed at a reduction of pancreatic cancer-related deaths.

Germline RTEL1 Variants in Telomere Biology Disorders

Rare germline variation in regulator of telomere elongation helicase 1 (RTEL1) is associated with telomere biology disorders (TBDs). Biallelic RTEL1 variants result in childhood onset dyskeratosis congenita and Hoyeraal-Hreidarsson syndrome whereas heterozygous individuals usually present later in life with pulmonary fibrosis or bone marrow failure. We compiled all TBD-associated RTEL1 variants in the literature and assessed phenotypes and outcomes of 44 individuals from 14 families with mono- or biallelic RTEL1 variants enrolled in clinical trial NCT00027274. Variants were classified by adapting ACMG-AMP guidelines using clinical information, telomere length, and variant allele frequency data. Compared with heterozygotes, individuals with biallelic RTEL1 variants had an earlier age at diagnosis (median age 35.5 vs. 5.1 years, p < 0.01) and worse overall survival (median age 66.5 vs. 22.9 years, p < 0.001). There were 257 unique RTEL1 variants reported in 47 publications, and 209 had a gnomAD minor allele frequency <1%. Only 38.3% (80/209) met pathogenic/likely pathogenic criteria. Notably, 8 of 209 reported disease-associated variants were benign or likely benign and the rest were variants of uncertain significance. Given the considerable differences in outcomes of TBDs associated with RTEL1 germline variants and the extent of variation in the gene, systematic functional studies and standardization of variant curation are urgently needed to inform clinical management.

Human oncostatin M deficiency underlies an inherited severe bone marrow failure syndrome

Oncostatin M (OSM) is a cytokine with the unique ability to interact with both the OSM receptor (OSMR) and the leukemia inhibitory factor receptor (LIFR). On the other hand, OSMR interacts with IL31RA to form the interleukin-31 receptor. This intricate network of cytokines and receptors makes it difficult to understand the specific function of OSM. While monoallelic loss-of-function (LoF) mutations in OSMR underlie autosomal dominant familial primary localized cutaneous amyloidosis, the in vivo consequences of human OSM deficiency have never been reported so far. Here, we identified 3 young individuals from a consanguineous family presenting with inherited severe bone marrow failure syndromes (IBMFS) characterized by profound anemia, thrombocytopenia, and neutropenia. Genetic analysis revealed a homozygous 1 base-pair insertion in the sequence of OSM associated with the disease. Structural and functional analyses showed that this variant causes a frameshift that replaces the C-terminal portion of OSM, which contains the FxxK motif that interacts with both OSMR and LIFR, with a neopeptide. The lack of detection and signaling of the mutant OSM suggests a LoF mutation. Analysis of zebrafish models further supported the role of the OSM/OSMR signaling in erythroid progenitor proliferation and neutrophil differentiation. Our study provides the previously uncharacterized and unexpectedly limited in vivo consequence of OSM deficiency in humans.

Different phenotypes with different endings-Telomere biology disorders and cancer predisposition with long telomeres

Rare germline pathogenic variants (GPVs) in genes essential in telomere length maintenance and function have been implicated in two broad classes of human disease. The telomere biology disorders (TBDs) are a spectrum of life-threatening conditions, including bone marrow failure, liver and lung disease, cancer and other complications caused by GPVs in telomere maintenance genes that result in short and/or dysfunctional telomeres and reduced cellular replicative capacity. In contrast, cancer predisposition with long telomeres (CPLT) is a disorder associated with elevated risk of a variety of cancers, primarily melanoma, thyroid cancer, sarcoma, glioma and lymphoproliferative neoplasms caused by GPVs in shelterin complex genes that lead to excessive telomere elongation and increased cellular replicative capacity. While telomeres are at the root of both disorders, the term TBD is used to convey the clinical phenotypes driven by critically short or otherwise dysfunctional telomeres and their biological consequences.

Inherited Predispositions to Myeloid Neoplasms: Pathogenesis and Clinical Implications

Myeloid neoplasms with and without preexisting platelet disorders frequently develop in association with an underlying germline predisposition. Germline alterations affecting ANKRD26, CEBPA, DDX41, ETV6, and RUNX1 are associated with nonsyndromic predisposition to the development of myeloid neoplasms including acute myeloid leukemia and myelodysplastic syndrome. However, germline predisposition to myeloid neoplasms is also associated with a wide range of other syndromes, including SAMD9/9L associated predisposition, GATA2 deficiency, RASopathies, ribosomopathies, telomere biology disorders, Fanconi anemia, severe congenital neutropenia, Down syndrome, and others. In the fifth edition of the World Health Organization (WHO) series on the classification of tumors of hematopoietic and lymphoid tissues, myeloid neoplasms associated with germline predisposition have been recognized as a separate entity. Here, we review several disorders from this WHO entity as well as other related conditions with an emphasis on the molecular pathogenesis of disease and accompanying somatic alterations. Finally, we provide an overview of establishing the molecular diagnosis of these germline genetic conditions and general recommendations for screening and management of the associated hematologic conditions.

Circulating TERT serves as the novel diagnostic and prognostic biomarker for the resectable NSCLC

BACKGROUND

Telomerase reverse transcriptase (TERT) is a catalytic subunit of telomerase and required for cancer development. This study aims to reveal its clinical utility for diagnosis and prognosis of resectable NSCLC.

METHODS

TERT was quantitatively evaluated by the enzyme-linked immunosorbent assay (ELISA) from 69 patients before and after the surgery. The prognostic value was evaluated by disease-free survival (DFS) and overall survival (OS).

RESULTS

Circulating TERT in NSCLC patients were significantly higher than that in the healthy group, possessing the AUC of 0.90. Importantly, TERT change between pre- and post- operation was significantly correlated with OS and DFS (p = 0.022, p = 0.046 respectively), acted as the independent prognostic factors for DFS and OS, indicating it can serve as the promising diagnostic and prognostic biomarker for resectable non-small cell lung cancer (NSCLC).

CONCLUSIONS

TERT change between pre- and post- resection can serve as the promising biomarker for prognosis of resectable NSCLC.

Rolling Circle Amplification Integrating with Exonuclease-III-Assisted Color Reaction for Sensitive Telomerase Activity Analysis

Telomerase activation can lead to the escape from cell senescence and immortalization, playing a crucial role in the growth and proliferation of cancer cells. Therefore, the detection of telomerase activity is essential for cancer diagnosis and treatment. Herein, we develop a novel ultrasensitive and visually detectable platform. By incorporation of exonuclease-III (Exo-III), this platform achieves dual signal amplification of rolling circle amplification products. Additionally, the colorimetric analysis of 3,3',5,5'-tetramethylbiphenyl (TMB) chromogenic reaction system provides this approach with unique advantages such as simplicity, speediness, and sensitivity. The detection platform exhibits high sensitivity and specificity in actual sample testing, which aligns closely with results obtained using commercial kits. Moreover, it offers ease-of-use through visual determination by the naked eyes. This finding indicates that our proposed sensing method performs satisfactorily in detecting telomerase in real biological samples. Henceforth, we believe that this sensing platform holds great potential for clinical diagnosis and anticancer drug development.

"Crying in the Wilderness"-The Use of Web-Based Support in Telomere Biology Disorders: Thematic Analysis

BACKGROUND

Web-based information and social support are commonly used in rare disease communities where geographic dispersion and limited provider expertise complicate in-person support. We examined web-based resource use among caregivers of individuals with telomere biology disorders (TBDs), which are rare genetic conditions with long diagnostic odysseys and uncertain prognoses including multiorgan system cancer risk.

OBJECTIVE

This study explored internet-based information-seeking and social support practices and perspectives of patients with TBDs and their caregivers.

METHODS

Our qualitative descriptive study used semistructured interviews of patients with TBDs and caregivers. Data were transcribed verbatim and thematically analyzed by an interdisciplinary team.

RESULTS

A total of 32 adults completed interviews. Participant ages ranged from 27 to 74 years. The majority (n=28, 88%) were female, occupied multiple TBD roles (eg, patient and parent), and had undergone genetic testing. Most engaged in web-based information-seeking (n=29, 91%) and TBD-specific social media (n=26, 81%). Participants found web-based resources useful for information-seeking but reported privacy concerns and frustration with forming supportive relationships. Most participants described ambivalence toward web-based resource use, citing tensions between hunger for information versus distrust, empowerment versus overwhelm, disclosure versus privacy, and accessibility versus connection. Fluctuations in web-based support use arose from perceived harms, information saturation, or decreased relevance over the course of TBD illness experience.

CONCLUSIONS

Individuals with TBDs and their caregivers reported frequent use of web-based informational and emotional support. However, ambivalence about the benefits and liabilities of web-based resources and persistent medical uncertainty may impact the adoption of and adherence to web-based support among patients with TBD and caregivers. Our findings suggest web-based psychosocial support should target long-term and multifaceted informational and emotional needs, be user-initiated, be offered alongside in-person formats, provide expert-informed information, and be attentive to personal privacy and evolving support needs of the TBD community. This study suggests web-based resources will be most effective in the TBD context when they achieve the following features: (1) offer a variety of ways to engage (eg, active and passive), (2) provide privacy protections in moderated "safe spaces" designed for personal disclosure, (3) offer separate venues for informational versus emotional support, (4) combine web-based relationship formation with opportunities for in-person gathering, (5) provide information that is reliable, easy to access, and informed by medical professionals, (6) remain mindful of user distress, and (7) are responsive to variations in levels and types of engagement. Additionally, advocacy organizations may wish to avoid traditional social media platforms when designing safe spaces for web-based emotional support, instead pivoting to internet-based tools that minimize privacy threats and limit the perpetual public availability of shared information.

Clonal hematopoiesis in cancer predisposition syndromes

After recent advances in sequencing technologies led to the discovery of novel genes associated with predisposition to hematological malignancies, studies have now shown that myeloid neoplasms associated with germline variants are more common than previously estimated. Based on these findings, myeloid neoplasms with germline predisposition have emerged as a unique category in the recent World Health Organization classification of Haematolymphoid Tumors. Clonal hematopoiesis is common in healthy individuals, particularly in older people. In patients with germline predisposition to hematological malignancies, clonal hematopoiesis is frequently observed at younger ages and is often associated with unique disease-specific driver mutations, some of which are hypothesized to compensate for the inherited defect. This review summarizes recent findings on clonal hematopoiesis in cancer predisposition syndromes.

Clonal landscape and clinical outcomes of telomere biology disorders: somatic rescue and cancer mutations

ABSTRACT

Telomere biology disorders (TBDs), caused by pathogenic germ line variants in telomere-related genes, present with multiorgan disease and a predisposition to cancer. Clonal hematopoiesis (CH) as a marker of cancer development and survival in TBDs is poorly understood. Here, we characterized the clonal landscape of a large cohort of 207 patients with TBD with a broad range of age and phenotype. CH occurred predominantly in symptomatic patients and in signature genes typically associated with cancers: PPM1D, POT1, TERT promoter (TERTp), U2AF1S34, and/or TP53. Chromosome 1q gain (Chr1q+) was the commonest karyotypic abnormality. Clinically, multiorgan involvement and CH in TERTp, TP53, and splicing factor genes were associated with poorer overall survival. Chr1q+ and splicing factor or TP53 mutations significantly increased the risk of hematologic malignancies, regardless of clonal burden. Chr1q+ and U2AF1S34 mutated clones were premalignant events associated with the secondary acquisition of mutations in genes related to hematologic malignancies. Similar to the known effects of Chr1q+ and TP53-CH, functional studies demonstrated that U2AF1S34 mutations primarily compensated for aberrant upregulation of TP53 and interferon pathways in telomere-dysfunctional hematopoietic stem cells, highlighting the TP53 pathway as a canonical route of malignancy in TBD. In contrast, somatic POT1/PPM1D/TERTp mutations had distinct trajectories unrelated to cancer development. With implications beyond TBD, our data show that telomere dysfunction is a strong selective pressure for CH. In TBD, CH is a poor prognostic marker associated with worse overall survival. The identification of key regulatory pathways that drive clonal transformation in TBD allows for the identification of patients at a higher risk of cancer development.

Genotype and Associated Cancer Risk in Individuals With Telomere Biology Disorders

Importance

Telomere biology disorders (TBDs) are inherited cancer-prone bone marrow failure syndromes with differences in morbidity and mortality based on mode of inheritance.

Objective

To quantify cancer risks in TBDs by genetic subgroups.

Design, Setting, and Participants

This longitudinal cohort study of TBDs assessed cancer occurrences from 2002 through 2022. Participants were individuals with a TBD-associated pathogenic germline variant recruited across institutions by self-referral. Data were collected and analyzed through June 30, 2022.

Exposures

The exposure was TBD genotypes, with subgroups defined by inheritance pattern (autosomal-dominant [AD-non-TINF2] vs autosomal-recessive/X-linked [AR/XLR] vs AD-TINF2).

Main Outcomes and Measures

The main outcome was cancer; secondary outcomes included death, or organ transplant. Cumulative cancer incidence was determined considering death or transplant as competing events. Observed:expected (O:E) ratios of cancer before and after any organ transplant were calculated using the National Cancer Institute's Surveillance, Epidemiology, and End Results Program.

Results

Among 230 individuals with TBD (135 [58.7%] male; median [range] age at last follow-up, 34.6 [1.4-82.2] years) included, the risk of cancer was 3-fold higher than the general population (O:E, 3.35 [95% CI, 2.32-4.68]). The highest risk was observed in individuals with AR/XLR (O:E, 19.16 [95% CI, 9.19-35.24]) with a significantly younger cancer onset than in individuals with AD-non-TINF2 (median [range] age, 36.7 [25.2-53.6] years vs 44.5 [32.2-67.5] years; P = .01). The risk of solid tumors was highest in individuals with AR/XLR (O:E = 23.97 [95% CI, 10.96-45.50]), predominantly head and neck squamous cell carcinomas (O:E, 276.00 [95% CI, 75.20-706.67]). Hematologic malignant neoplasm risk was highest in individuals with AD-non-TINF2 (O:E, 9.41 [95% CI, 4.30-17.86]). Solid tumor cumulative incidence increased to 12% for individuals with AR/XLR by age 45 years and to 13% for individuals with AD-non-TINF2 by age 70 years. The cumulative incidence of hematologic malignant neoplasms leveled off at 2% by age 30 years and 19% by age 70 years in individuals with AR/XLR and AD-non-TINF2, respectively. Individuals with AD-TINF2 showed the highest cumulative incidence for transplant or death (49% by age 15 years). Following transplant, individuals with AR/XLR (O:E, 136.11 [95% CI, 54.72-280.44) or AD-TINF2 (O:E, 81.07 [95% CI, 16.72-236.92]) had the highest cancer risk, predominantly young-onset head and neck squamous cell carcinomas (median [range] age, 32.2 [10.5-35.5] years).

Conclusions and Relevance

This cohort study of individuals with TBDs found an increased cancer risk compared with the general population, with the earliest age at onset for individuals with AR/XLR inheritance. Cancer risks increased after organ transplant across all subgroups. These differences in TBD-associated cancer risks by mode of inheritance suggest cancer screening could be tailored by genotype, but additional research is warranted.

Defining the complex needs of families with rare diseases-the example of telomere biology disorders

Families with rare diseases, such as telomere biology disorders (TBDs), may have extensive unmet needs given the heterogeneity, chronicity, and potential severity of illness. TBDs are rare inherited syndromes associated with high risk of bone marrow failure, cancer, pulmonary fibrosis, and other severe, chronic complications. To identify gaps in clinical care, we aimed to ascertain the perceived unmet needs of adults and family caregivers, current or bereaved, of individuals with TBDs. Participants were aged ≥18 years with a self-reported TBD diagnosis and/or ever caregivers to one or more family members with a TBD. Participants completed an online survey (N = 35) and/or an audio-recorded telephone interview (N = 32). We calculated descriptive statistics in SPSS and thematically analyzed interview transcripts. Quantitative and qualitative data were analyzed concurrently. Most participants were aged ≥35 years, female, highly educated, and medically insured. Survey respondents reported numerous unmet needs in psychosocial, medical, financial, and daily activity domains. In interviews, participant descriptions validated and contextualized the salience of these unmet needs. Both qualitative and quantitative data identified critical shortfalls in addressing chronic family distress and specialty care coordination. Adults and caregivers of individuals with TBDs have a high risk of adverse psychosocial sequelae given extensive unmet needs. These findings provide a foundation for understanding the range and extent of gaps in care for families with rare diseases, especially TBDs but that are likely applicable to others. Tailored multi-disciplinary interventions involving patients, families, clinicians, researchers, and patient advocacy communities are required to appropriately address care needs for all rare diseases.

Telomere biology disorders: from dyskeratosis congenita and beyond

Defective telomerase function or telomere maintenance causes genomic instability. Alterations in telomere length and/or attrition are the primary features of rare diseases known as telomere biology disorders or telomeropathies. Recent advances in the molecular basis of these disorders and cutting-edge methods assessing telomere length have increased our understanding of this topic. Multiorgan manifestations and different phenotypes have been reported even in carriers within the same family. In this context, apart from dyskeratosis congenita, disorders formerly considered idiopathic (i.e. pulmonary fibrosis, liver cirrhosis) frequently correlate with underlying defective telomere maintenance mechanisms. Moreover, these patients are prone to developing specific cancer types and exhibit exceptional sensitivity and toxicity in standard chemotherapy regimens. The current review describes the diverse spectrum of clinical manifestations of telomere biology disorders in pediatric and adult patients, their correlation with pathogenic variants, and considerations during their management to increase awareness and improve a multidisciplinary approach.

Haematological features of telomere biology disorders diagnosed in adulthood: A French nationwide study of 127 patients

Data on haematological features of telomere biology disorders (TBD) remain scarce. We describe haematological, extra-haematological characteristics and prognosis of 127 genetically confirmed TBD patients diagnosed after the age of 15. Ninety-three index cases and 34 affected relatives were included. At diagnosis of TBD, 76.3% of index cases had haematological features, half pulmonary features and a third liver features. At diagnosis, bone marrow failure (BMF) was present in 59 (46.5%), myelodysplastic syndrome (MDS) in 22 (17.3%) and acute myeloid leukaemia (AML) in 2 (1.6%) while 13 (10.2%) developed or worsened bone marrow involvement during follow-up. At diagnosis, compared to MDS/AML patients, BMF patients were younger (median 23.1 years vs. 43.8, p = 0.007), and had a better outcome (4-year overall survival 76.3% vs. 31.8%, p < 0.001). While frequencies and burden of cytogenetical and somatic mutations increased significantly in myeloid malignancies, some abnormalities were also observed in patients with normal blood counts and BMF, notably somatic spliceosome variants. Solid cancers developed in 8.7% patients, mainly human papillomavirus-related cancers and hepatocellular carcinomas. TBD is a multiorgan progressive disease. While BMF is the main haematological disorder, high-risk myeloid malignancies are common, and are, together with age, the only factors associated with a worse outcome.

Telomere maintenance and the DNA damage response: a paradoxical alliance

Telomeres are the protective caps at the ends of linear chromosomes of eukaryotic organisms. Telomere binding proteins, including the six components of the complex known as shelterin, mediate the protective function of telomeres. They do this by suppressing many arms of the canonical DNA damage response, thereby preventing inappropriate fusion, resection and recombination of telomeres. One way this is achieved is by facilitation of DNA replication through telomeres, thus protecting against a "replication stress" response and activation of the master kinase ATR. On the other hand, DNA damage responses, including replication stress and ATR, serve a positive role at telomeres, acting as a trigger for recruitment of the telomere-elongating enzyme telomerase to counteract telomere loss. We postulate that repression of telomeric replication stress is a shared mechanism of control of telomerase recruitment and telomere length, common to several core telomere binding proteins including TRF1, POT1 and CTC1. The mechanisms by which replication stress and ATR cause recruitment of telomerase are not fully elucidated, but involve formation of nuclear actin filaments that serve as anchors for stressed telomeres. Perturbed control of telomeric replication stress by mutations in core telomere binding proteins can therefore cause the deregulation of telomere length control characteristic of diseases such as cancer and telomere biology disorders.

Connecting the Dots: Telomere Shortening and Rheumatic Diseases

Telomeres, repetitive sequences located at the extremities of chromosomes, play a pivotal role in sustaining chromosomal stability. Telomerase is a complex enzyme that can elongate telomeres by appending telomeric repeats to chromosome ends and acts as a critical factor in telomere dynamics. The gradual shortening of telomeres over time is a hallmark of cellular senescence and cellular death. Notably, telomere shortening appears to result from the complex interplay of two primary mechanisms: telomere shelterin complexes and telomerase activity. The intricate interplay of genetic, environmental, and lifestyle influences can perturb telomere replication, incite oxidative stress damage, and modulate telomerase activity, collectively resulting in shifts in telomere length. This age-related process of telomere shortening plays a considerable role in various chronic inflammatory and oxidative stress conditions, including cancer, cardiovascular disease, and rheumatic disease. Existing evidence has shown that abnormal telomere shortening or telomerase activity abnormalities are present in the pathophysiological processes of most rheumatic diseases, including different disease stages and cell types. The impact of telomere shortening on rheumatic diseases is multifaceted. This review summarizes the current understanding of the link between telomere length and rheumatic diseases in clinical patients and examines probable telomere shortening in peripheral blood mononuclear cells and histiocytes. Therefore, understanding the intricate interaction between telomere shortening and various rheumatic diseases will help in designing personalized treatment and control measures for rheumatic disease.

Causality between Telomere Length and the Risk of Hematologic Malignancies: A Bidirectional Mendelian Randomization Study

Growing evidence indicates a relationship between telomere length (TL) and the stage, prognosis, and treatment responsiveness of hematopoietic malignancies. However, the relationship between TL and the risk of hematologic malignancies remains unclear, considering the vulnerability of observational studies to potential confounding and reverse causation. A two-sample bidirectional Mendelian randomization (MR) analysis was conducted utilizing publicly available genome-wide association study data to assess whether TL was causally associated with the risk of hematologic malignancies. The inverse variance weighted approach was used as the primary assessment approach to evaluate the effects of the causes, augmented by the weighted median and MR-Egger methods. Cochran's Q test, MR-Egger intercept test, MR-Pleiotropy Residual Sum and Outlier test, and leave-one-out analysis were performed to evaluate sensitivity, heterogeneity, and pleiotropy. According to forward MR estimations, longer TL was related to an increased risk of acute lymphocytic leukemia (OR = 2.690; P = 0.041), chronic lymphocytic leukemia (OR = 2.155; P = 0.005), multiple myeloma (OR = 1.845; P = 0.024), Hodgkin lymphoma (OR = 1.697; P = 0.014), and non-Hodgkin lymphoma (OR = 1.737; P = 0.009). Specific types of non-Hodgkin lymphoma were also associated with TL. The reverse MR results revealed that hematologic malignancies had no effect on TL. This MR analysis revealed an association between longer TL and an increased risk of specific hematologic malignancies, indicating a potential role of TL in risk evaluation and management in hematologic malignancies.

SIGNIFICANCE

In contrast to observational studies, this study uncovered the reliable causal relationships between TL and hematologic malignancies, emphasizing the potential role of telomeres in tumor development. TL maintenance may offer a promising strategy to reduce the risk of hematologic malignancies.

Alemtuzumab-based conditioning regimen before hematopoietic stem cell transplantation in patients with short telomere syndromes: a retrospective study of the SFGM-TC

While HSCT is the only curative option for patients with short telomere syndromes (STSs) and severe bone marrow failure (BMF) or myeloid malignancies (MM), their increase sensitivity to conditioning regimen strongly affect outcomes. To minimize HSCT related mortality, alemtuzumab-based conditioning regimens have been proposed, but the number of patients transplanted with those regimens reported in the literature remains very low. We retrospectively analyzed outcome of adults and adolescents with STSs transplanted after an alemtuzumab, fludarabine and cyclophosphamide based regimen registered by the SFGM-TC. Seven patients were transplanted for a BMF and 5 for a MM (median age 34 years, (IQR [22-45])). The 2-year GRFS for patients with MM was 20% (95% CI [3;100]), and 57% (95% CI [30;100]) in others. In univariate (hazard ratio, HR = 6, 95% CI [1;31]) and multivariate analysis (HR = 26, 95% CI [2;414]) stem cell source was a predictive factor for GRFS. Three of the 5 patients with pre-transplant MM relapsed and 2 of them died at last follow up. The 2-year OS was 66% (95% CI [43;99]) in the whole cohort with a median follow up of 32 months (IQR [13-56]). In conclusion, Alemtuzumab-based conditioning regimen with bone marrow is an option for patients with STSs and BMF, but others modalities have to be explored for patients with MM.

The evolving genetic landscape of telomere biology disorder dyskeratosis congenita

Dyskeratosis congenita (DC) is a rare inherited bone marrow failure syndrome, caused by genetic mutations that principally affect telomere biology. Approximately 35% of cases remain uncharacterised at the genetic level. To explore the genetic landscape, we conducted genetic studies on a large collection of clinically diagnosed cases of DC as well as cases exhibiting features resembling DC, referred to as 'DC-like' (DCL). This led us to identify several novel pathogenic variants within known genetic loci and in the novel X-linked gene, POLA1. In addition, we have also identified several novel variants in POT1 and ZCCHC8 in multiple cases from different families expanding the allelic series of DC and DCL phenotypes. Functional characterisation of novel POLA1 and POT1 variants, revealed pathogenic effects on protein-protein interactions with primase, CTC1-STN1-TEN1 (CST) and shelterin subunit complexes, that are critical for telomere maintenance. ZCCHC8 variants demonstrated ZCCHC8 deficiency and signs of pervasive transcription, triggering inflammation in patients' blood. In conclusion, our studies expand the current genetic architecture and broaden our understanding of disease mechanisms underlying DC and DCL disorders.

Inherited Telomere Biology Disorders: Pathophysiology, Clinical Presentation, Diagnostics, and Treatment

Background

Telomeres are the end-capping structures of all eukaryotic chromosomes thereby protecting the genome from damage and degradation. During the aging process, telomeres shorten continuously with each cell division until critically short telomeres prevent further proliferation whereby cells undergo terminal differentiation, senescence, or apoptosis. Premature aging due to critically short telomere length (TL) can also result from pathogenic germline variants in the telomerase complex or related genes that typically counteract replicative telomere shortening in germline and certain somatic cell populations, e.g., hematopoetic stem cells. Inherited diseases that result in altered telomere maintenance are summarized under the term telomere biology disorder (TBD).

Summary

Since TL both reflects but more importantly restricts the replicative capacity of various human tissues, a sufficient telomere reserve is particularly important in cells with high proliferative activity (e.g., hematopoiesis, immune cells, intestinal cells, liver, lung, and skin). Consequently, altered telomere maintenance as observed in TBDs typically results in premature replicative cellular exhaustion in the respective organ systems eventually leading to life-threatening complications such as bone marrow failure (BMF), pulmonary fibrosis, and liver cirrhosis.

Key Messages

The recognition of a potential congenital origin in approximately 10% of adult patients with clinical BMF is of utmost importance for the proper diagnosis, appropriate patient and family counseling, to prevent the use of inefficient treatment and to avoid therapy-related toxicities including appropriate donor selection when patients have to undergo stem cell transplantation from related donors. This review summarizes the current state of knowledge about TBDs with particular focus on the clinical manifestation patterns in children (termed early onset TBD) compared to adults (late-onset TBD) including typical treatment- and disease course-related complications as well as their prognosis and adequate therapy. Thereby, it aims to raise awareness for a disease group that is currently still highly underdiagnosed particularly when it first manifests itself in adulthood.

The gray boundaries of aberrant shortening of the cellular timekeepers' edges

N. Meza and G. Guenechea discuss novel genetic variants identified in telomere biology disorder dyskeratosis congenita (DC) and DC-like patients, as reported by Tummala and colleagues in this issue of EMBO Mol Med .

ZCCHC8 p.P410A disrupts nucleocytoplasmic localization, promoting idiopathic pulmonary fibrosis and chronic obstructive pulmonary disease

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a special kind of chronic interstitial lung disease with insidious onset. Previous studies have revealed that mutations in ZCCHC8 may lead to IPF. The aim of this study is to explore the ZCCHC8 mutations in Chinese IPF patients.

METHODS

Here, we enrolled 124 patients with interstitial lung disease from 2017 to 2023 in our hospital. Whole exome sequencing and Sanger sequencing were employed to explore the genetic lesions of these patients.

RESULTS

Among these 124 patients, a novel mutation (NM_017612: c.1228 C > G/p.P410A) of Zinc Finger CCHC-Type Containing 8 (ZCCHC8)was identified in a family with IPF and chronic obstructive lung disease. As a component of the nuclear exosome-targeting complex that regulates the turnover of human telomerase RNA, ZCCHC8 mutations have been reported may lead to IPF in European population and American population. Functional study confirmed that the novel mutation can disrupt the nucleocytoplasmic localization of ZCCHC8, which further decreased the expression of DKC1 and RTEL1, and finally reduced the length of telomere and led to IPF and related disorders.

CONCLUSIONS

We may first report the ZCCHC8 mutation in Asian population with IPF. Our study broadens the mutation, phenotype, and population spectrum of ZCCHC8 deficiency.

Genetic architecture of telomere length in 462,666 UK Biobank whole-genome sequences

Telomeres protect chromosome ends from damage and their length is linked with human disease and aging. We developed a joint telomere length metric, combining quantitative PCR and whole-genome sequencing measurements from 462,666 UK Biobank participants. This metric increased SNP heritability, suggesting that it better captures genetic regulation of telomere length. Exome-wide rare-variant and gene-level collapsing association studies identified 64 variants and 30 genes significantly associated with telomere length, including allelic series in ACD and RTEL1. Notably, 16% of these genes are known drivers of clonal hematopoiesis-an age-related somatic mosaicism associated with myeloid cancers and several nonmalignant diseases. Somatic variant analyses revealed gene-specific associations with telomere length, including lengthened telomeres in individuals with large SRSF2-mutant clones, compared with shortened telomeres in individuals with clonal expansions driven by other genes. Collectively, our findings demonstrate the impact of rare variants on telomere length, with larger effects observed among genes also associated with clonal hematopoiesis.

Deciphering the causal association and underlying transcriptional mechanisms between telomere length and abdominal aortic aneurysm

Background

The purpose of this study is to investigate the causal effect and potential mechanisms between telomere length and abdominal aortic aneurysm (AAA).

Methods

Summary statistics of telomere length and AAA were derived from IEU open genome-wide association studies and FinnGen R9, respectively. Bi-directional Mendelian randomization (MR) analysis was conducted to reveal the causal relationship between AAA and telomere length. Three transcriptome datasets were retrieved from the Gene Expression Omnibus database and telomere related genes was down-loaded from TelNet. The overlapping genes of AAA related differentially expressed genes (DEGs), module genes, and telomere related genes were used for further investigation. Telomere related diagnostic biomarkers of AAA were selected with machine learning algorisms and validated in datasets and murine AAA model. The correlation between biomarkers and immune infiltration landscape was established.

Results

Telomere length was found to have a suggestive negative associations with AAA [IVW, OR 95%CI = 0.558 (0.317-0.701), P < 0.0001], while AAA showed no suggestive effect on telomere length [IVW, OR 95%CI = 0.997 (0.990-1.004), P = 0.4061]. A total of 40 genes was considered as telomere related DEGs of AAA. PLCH2, PRKCQ, and SMG1 were selected as biomarkers after multiple algorithms and validation. Immune infiltration analysis and single cell mRNA analysis revealed that PLCH2 and PRKCQ were mainly expressed on T cells, while SMG1 predominantly expressed on T cells, B cells, and monocytes. Murine AAA model experiments further validated the elevated expression of biomarkers.

Conclusion

We found a suggestive effect of telomere length on AAA and revealed the potential biomarkers and immune mechanism of telomere length on AAA. This may shed new light for diagnosis and therapeutics on AAA.

Causal Relationship between Aging and Anorexia Nervosa: A White-Matter-Microstructure-Mediated Mendelian Randomization Analysis

This study employed a two-step Mendelian randomization analysis to explore the causal relationship between telomere length, as a marker of aging, and anorexia nervosa and to evaluate the mediating role of changes in the white matter microstructure across different brain regions. We selected genetic variants associated with 675 diffusion magnetic resonance imaging phenotypes representing changes in brain white matter. F-statistics confirmed the validity of the instruments, ensuring robust causal inference. Sensitivity analyses, including heterogeneity tests, horizontal pleiotropy tests, and leave-one-out tests, validated the results. The results show that telomere length is significantly negatively correlated with anorexia nervosa in a unidirectional manner (p = 0.017). Additionally, changes in specific white matter structures, such as the internal capsule, corona radiata, posterior thalamic radiation, left cingulate gyrus, left longitudinal fasciculus, and left forceps minor (p < 0.05), were identified as mediators. These findings enhance our understanding of the neural mechanisms, underlying the exacerbation of anorexia nervosa with aging; emphasize the role of brain functional networks in disease progression; and provide potential biological targets for future therapeutic interventions.