Mutations In Telomerase Genes Research Articles

Telomere-mediated lung disease.

Parenchymal lung disease is the fourth leading cause of death in the United States; among the top causes, it continues on the rise. Telomeres and telomerase have historically been linked to cellular processes related to aging and cancer, but surprisingly, in the recent decade genetic discoveries have linked the most apparent manifestations of telomere and telomerase dysfunction in humans to the etiology of lung disease: both idiopathic pulmonary fibrosis (IPF) and emphysema. The short telomere defect is pervasive in a subset of IPF patients, and human IPF is the phenotype most intimately tied to germline defects in telomere maintenance. One-third of families with pulmonary fibrosis carry germline mutations in telomerase or other telomere maintenance genes, and one-half of patients with apparently sporadic IPF have short telomere length. Beyond explaining genetic susceptibility, short telomere length uncovers clinically relevant syndromic extrapulmonary disease, including a T-cell immunodeficiency and a propensity to myeloid malignancies. Recognition of this subset of patients who share a unifying molecular defect has provided a precision medicine paradigm wherein the telomere-mediated lung disease diagnosis provides more prognostic value than histopathology or multidisciplinary evaluation. Here, we critically evaluate this progress, emphasizing how the genetic findings put forth a new pathogenesis paradigm of age-related lung disease that links telomere abnormalities to alveolar stem senescence, remodeling, and defective gas exchange.

KLF4 regulates TERT expression in alveolar epithelial cells in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) was considered as a telomere-mediated disease. TERT and TERC correlated with telomere length. Although telomerase gene mutations were associated with IPF, majority patients did not carry mutations. The mechanism by which telomerase expression was regulated in IPF are still unclear. In this study, we aimed to delineate the mechanisms that how TERT protein expression were regulated in alveolar epithelial cells (AECs) in pulmonary fibrosis. Here, we found that P16, P21 and fibrosis markers (αSMA and Collagen-I) were prominently increased in lung tissues of IPF patients and bleomycin-induced mouse models, while the expression of KLF4 and TERT were decreased in AECs. In vivo experiments, AAV-6 vectors mediated KLF4 over-expression with specific SP-C promoter was constructed. Over-expression of KLF4 in AECs could protect TERT expression and suppress the development of pulmonary fibrosis in bleomycin-induced mouse models. In the mechanism exploration of TERT regulation, KLF4 and TERT were both down-regulated in bleomycin-induced senescent MLE-12 and BEAS-2B cells. Compared with control group, small-interfering RNA targeting KLF4 significantly reduced the TERT expression and telomerase activity, while overexpression of KLF4 can increased the expression of TERT and telomerase activity in senescent AECs. Furthermore, ChIP showed that KLF4 protein could bind to the TERT promoter region in MLE-12 cells, suggesting that KLF4 could implicate in pathogenesis of lung fibrosis through regulating TERT transcription in AECs. Taken together, this study identified that KLF4 might be a promising potential target for further understanding the mechanism and developing novel strategy for the treatment of lung fibrosis in IPF.

Differential immunohistochemical expression of hTERT in lung cancer patients with and without idiopathic pulmonary fibrosis

BackgroundHuman telomerase reverse transcriptase (hTERT) is the catalytic subunit of telomerase enzyme, which adds nucleotides to telomeres and counteracts their length shortening. The development of a telomere maintenance mechanism represents a hallmark of cancer. On the other hand, idiopathic pulmonary fibrosis (IPF) is associated with mutations in telomerase genes and shorter telomeres. IPF is frequently complicated with lung cancer. AimTo investigate the expression of hTERT in lung cancer with co-existing IPF and to compare with lung cancer without fibrosis. MethodsDiagnostic lung cancerous biopsies were retrieved from 18 patients with lung cancer and concomitant IPF, as well as 18 age and gender matched controls with lung cancer without pulmonary fibrosis. The expression of hTERT was studied with immunohistochemistry. ImajeJ software was used to quantitate subcellular stain intensity. Immunohistochemical investigation of two senescence-associated markers, p16 and p21, was also performed in all 36 cases. ResultsBoth groups highly expressed hTERT, without significant difference (100% vs 95%, p = 0.521). Evaluation of p16 and p21 immunostaining revealed negative to minimal immunoreactivity in both groups. hTERT localization exhibited higher median nuclear intensity in the group of lung cancer with IPF (0.62 vs 0.45, p = 0.016), while cytoplasmic intensity did not differ significantly (0.17 vs 0.15, p = 0.463). Higher median nuclear intensity was also correlated with small cell lung cancer subtype in the whole study sample (0.69 vs 0.45, p = 0.09). ConclusionhTERT is highly expressed in lung cancer with concomitant IPF, but with differential localization compared to lung cancer without IPF, implying differences in pathogenicity and requiring further investigation.

Utility of Telomerase Gene Mutation Testing in Patients with Idiopathic Pulmonary Fibrosis in Routine Practice.

Recent studies have suggested that causative variants in telomerase complex genes (TCGs) are present in around 10% of individuals with idiopathic pulmonary fibrosis (IPF) regardless of family history of the disease. However, the studies used a case-control rare variant enrichment study design which is not directly translatable to routine practice. To validate the prevalence results and to establish the individual level, routine clinical practice, and utility of those results we performed next generation sequencing of TCGs on a cohort of well-characterized consecutive individuals with IPF (diagnosis established according to ATS/ERS/JRS/ALAT guidelines). Of 27 IPF patients, three had a family history of idiopathic interstitial pneumonia (familial IPF) and 24 did not (sporadic IPF). Pathogenic/likely-pathogenic variants (according to American College of Medical Genetics criteria) in TCG were found in three individuals (11.1%) of the whole cohort; specifically, they were present in 2 out of 24 (8.3%) of the sporadic and in 1 out of 3 (33.3%) of the patients with familial IPF. Our results, which were established on an individual-patient level study design and in routine clinical practice (as opposed to the case-control study design), are roughly in line with the around 10% prevalence of causative TCG variants in patients with IPF.

Somatic reversion impacts myelodysplastic syndromes and acute myeloid leukemia evolution in the short telomere disorders

BACKGROUNDGermline mutations in telomerase and other telomere maintenance genes manifest in the premature aging short telomere syndromes. Myelodysplastic syndromes and acute myeloid leukemia (MDS/AML) account for 75% of associated malignancies, but how these cancers overcome the inherited telomere defect is unknown.METHODSWe used ultra-deep targeted sequencing to detect somatic reversion mutations in 17 candidate telomere lengthening genes among controls and patients with short telomere syndromes with and without MDS/AML, and we tested the functional significance of these mutations.RESULTSWhile no controls carried somatic mutations in telomere maintenance genes, 29% (16 of 56) of adults with germline telomere maintenance defects carried at least 1 (P < 0.001), and 13% (7 of 56) had 2 or more. In addition to TERT promoter mutations, which were present in 19%, another 13% of patients carried a mutation in POT1 or TERF2IP. POT1 mutations impaired telomere binding in vitro and some mutations were identical to ones seen in familial melanoma associated with longer telomere length. Exclusively in patients with germline defects in telomerase RNA (TR), we identified somatic mutations in nuclear RNA exosome genes RBM7, SKIV2L2, and DIS3, where loss-of-function upregulates mature TR levels. Somatic reversion events in 6 telomere-related genes were more prevalent in patients who were MDS/AML-free (P = 0.02, RR 4.4, 95% CI 1.2-16.7), and no patient with MDS/AML had more than 1 reversion mutation.CONCLUSIONOur data indicate that diverse adaptive somatic mutations arise in the short telomere syndromes. Their presence may alleviate the telomere crisis that promotes transformation to MDS/AML.FUNDINGThis work was supported by the NIH, the Commonwealth Foundation, the S&R Foundation Kuno Award, the Williams Foundation, the Vera and Joseph Dresner Foundation, the MacMillan Pathway to Independence Award, the American Society of Hematology Scholar Award, the Johns Hopkins Research Program for Medical Students, and the Turock Scholars Fund.

Liver Transplantation in Short Telomere-Mediated Hepatopulmonary Syndrome Following Bone Marrow Transplantation Using HCV Positive Allografts: A Case Series.

Short telomere syndromes (STS) are the most common premature aging disorders; mutations in telomerase and other telomere maintenance genes underlie their etiology(1). Their biology is defined by short telomere length which provokes senescence and apoptosis, leading to organ failure. The majority of STS are autosomal dominant, but X-linked, de novo and recessive forms exist.

Detection of Clonal Hematopoiesis Is a Rare Event in Patients with Dyskeratosis Congenita

Introduction: Telomeres shorten with each cell division and reflect the replicative history of a cell. Cells undergo replicative senescence when reaching a critically short telomere length (TL) or alternatively, may undergo clonal evolution due to increasing genetic instability. Thus, dependent of the integrity of the respective checkpoints, telomere shortening on the one hand represents an established predisposing factor for malignant transformation while on the other hand it is a known tumor suppressor mechanism.Dyskeratosis Congenita (DKC) is a multisystem disorder characterized by bone marrow failure, increased risk of cancer development and critically short telomeres. Premature telomere shortening is frequently caused by mutations in telomerase or related genes leading to reduced functional telomerase activity. In various acquired bone marrow failure syndromes, such as aplastic anemia, premature telomere shortening was linked to mutations in genes typically found in clonal disorders such as myelodysplastic syndromes (MDS). For patients with inherited DKC, no data is available about the frequency of gene mutations related to clonal hematopoiesis. In this study, we aimed to analyze MDS-related genes in patients with molecularly confirmed DKC.Methods and Patients: Analysis included 13 patients from the Aachen Telomeropathy Registry and the Freiburg pediatric MDS registry. All patients had molecularly confirmed mutations in DKC related genes (TERC n=6, TERT n=6, DKC1 n=1). TL was measured by flow-FISH. Next-generation sequencing (NGS) was carried out on peripheral blood due to the hypoplastic/aplastic bone marrow. A self-customized NGS panel (“telomere-panel”) for telomeropathy-causing genes (CTC1, DKC1, NHP2, NOP10, RTEL1, TERC, TERT, TCAB1, TINF2, USB1) was used to detect DKC-associated gene mutations and especially, the allele burden of each mutation to identify any deviation (of expected 50%) in the allele ratio of the underlying DKC causing mutation. Furthermore, we used a self-designed NGS-panel (“MDS/MPN-panel”) including genes harboring mutations which are associated with myelodysplastic syndrome, e.g. as markers for clonal hematopoesis (ABL, ASXL1, BARD, CALR, CBL, CEBPA, CHEK2, CSF3R, DNMT3A, ETNK1, ETV6, EZH2, IDH1, IDH2, JAK2, KIT, KRAS, MPL, NFE2, NRAS, PDGFRA, PTPN11, RUNX1, SETBP1, SF3A1, SF3B1, SH3B2 (LNK), SRSF2, TCF12, TET2, TP53, U2AF1). Again, allele burden was analyzed for all detected mutations.Results: Telomere lengthwas found to be below the first percentile in the lymphocytes of the peripheral blood in all 13 patients. Mean TL was 4.77 kb±0.66SD in the lymphocytes and 5.28kb±0.92SD in the granulocyte subpopulation, respectively. Regarding the performance of the NGS analysis, quality parameters were good (Q30>85%) and for both panels 95% of the expected area was covered with a coverage of >300 (MDS/MPN-panel) and >100 (telomere-panel). Using the “telomere-panel”, all detected mutations showed a mutational allele burden of about 50%, most likely according to heterozygosity of the detected mutations. Applying the “MDS-panel”, only 2 out of 13 patients revealed relevant MDS-linked mutations. One patient harbored a U2AF1 gene mutation (c.101C>T, p.Ser34Phe; allele burden 16%), recently described in MDS as acquired mutation and thus classified as pathogenic without further confirmation in addition to a DKC-causing TERT mutation (c.2915G>A; p.Arg972His). In another patient with an inherited TERC mutation, the ASXL1 variant (c.3244_3246CTGdel; freq.: 48% [4708/9347]; p.Leu1082del) was detected. This variant is being discussed to be pathogenic as bystander or rare germline variant (mean allele frequency /dbsnp: 0,002%). Finally, mean telomere length in granulocytes did not differ between patients with detected MDS-linked mutations (4.77 kb) and without mutations (4.78kb).Conclusions: In patients with DKC, clonal hematopoiesis with detection of MDS-related genes can be detected but is a rare event compared to other myeloid diseases associated with short telomeres, suggesting independence of clonal hematopoiesis from telomere length. Genetic mosaicism or epigenetic factors (e.g. genomic imprinting) can be discussed as a mechanism to allow clonal expansion in telomeropathies, but further studies are needed to elucidate the mechanism how cells carrying impaired telomerase activity can progress to clonality. DisclosuresCorbacioglu:Jazz Pharmaceuticals: Consultancy, Honoraria. Koschmieder:BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Roche: Other: Clinical Trial participation; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support. Brummendorf:Takeda Pharmaceuticals International Co: Consultancy, Research Funding.

TPP1 mutagenesis screens unravel shelterin interfaces and functions in hematopoiesis.

Telomerase catalyzes chromosome end replication in stem cells and other long-lived cells. Mutations in telomerase or telomere-related genes result in diseases known as telomeropathies. Telomerase is recruited to chromosome ends by the ACD/TPP1 protein (TPP1 hereafter), a component of the shelterin complex that protects chromosome ends from unwanted end joining. TPP1 facilitates end protection by binding shelterin proteins POT1 and TIN2. TPP1 variants have been associated with telomeropathies but remain poorly characterized in vivo. Disease variants and mutagenesis scans provide efficient avenues to interrogate the distinct physiological roles of TPP1. Here, we conduct mutagenesis in the TIN2- and POT1-binding domains of TPP1 to discover mutations that dissect TPP1’s functions. Our results extend current structural data to reveal that the TPP1-TIN2 interface is more extensive than previously thought and highlight the robustness of the POT1-TPP1 interface. Introduction of separation-of-function mutants alongside known TPP1 telomeropathy mutations in mouse hematopoietic stem cells (mHSCs) lacking endogenous TPP1 demonstrated a clear phenotypic demarcation. TIN2- and POT1-binding mutants were unable to rescue mHSC failure resulting from end deprotection. In contrast, TPP1 telomeropathy mutations sustained mHSC viability, consistent with their selectively impacting end replication. These results highlight the power of scanning mutagenesis in revealing structural interfaces and dissecting multifunctional genes.

Cancer spectrum and outcomes in the Mendelian short telomere syndromes

AbstractShort telomeres have been linked to cancer risk, yet other evidence supports them being tumor suppressive. Here, we report cancer outcomes in individuals with germline mutations in telomerase and other telomere-maintenance genes. Among 180 individuals evaluated in a hospital-based setting, 12.8% had cancer. Solid tumors were rare (2.8%); nearly all were young male DKC1 mutation carriers, and they were generally resectable with good short-term outcomes. Myelodysplastic syndrome (MDS) was most common, followed by acute myeloid leukemia (AML); they accounted for 75% of cancers. Age over 50 years was the biggest risk factor, and MDS/AML usually manifested with marrow hypoplasia and monosomy 7, but the somatic mutation landscape was indistinct from unselected patients. One- and 2-year survival were 61% and 39%, respectively, and two-thirds of MDS/AML patients died of pulmonary fibrosis and/or hepatopulmonary syndrome. In one-half of the cases, MDS/AML patients showed a recurrent peripheral blood pattern of acquired, granulocyte-specific telomere shortening. This attrition was absent in age-matched mutation carriers who did not have MDS/AML. We tested whether adult short telomere patients without MDS/AML also had evidence of clonal hematopoiesis of indeterminate potential–related mutations and found that 30% were affected. These patients also primarily suffered morbidity from pulmonary fibrosis during follow-up. Our data show that the Mendelian short telomere syndromes are associated with a relatively narrow cancer spectrum, primarily MDS and AML. They suggest that short telomere length is sufficient to drive premature age-related clonal hematopoiesis in these inherited disorders.

Telomere dysfunction impairs epidermal stem cell specification and differentiation by disrupting BMP/pSmad/P63 signaling.

Telomere shortening is associated with aging and age-associated diseases. Additionally, telomere dysfunction resulting from telomerase gene mutation can lead to premature aging, such as apparent skin atrophy and hair loss. However, the molecular signaling linking telomere dysfunction to skin atrophy remains elusive. Here we show that dysfunctional telomere disrupts BMP/pSmad/P63 signaling, impairing epidermal stem cell specification and differentiation of skin and hair follicles. We find that telomere shortening mediated by Terc loss up-regulates Follistatin (Fst), inhibiting pSmad signaling and down-regulating P63 and epidermal keratins in an ESC differentiation model as well as in adult development of telomere-shortened mice. Mechanistically, short telomeres disrupt PRC2/H3K27me3-mediated repression of Fst. Our findings reveal that skin atrophy due to telomere dysfunction is caused by a previously unappreciated link with Fst and BMP signaling that could be explored in the development of therapies.

Heterozygous CTC1 Variants in Acquired Bone Marrow Failure

Germ line (GL) alterations of telomerase machinery genes may lead to inherited telomeropathies, but recent analysis of large control populations revealed that some of the previously assumed pathologic variants are present in comparable frequencies in healthy individuals. Pathogenic telomerase gene variants can be found, but are rare in idiopathic aplastic anemia (AA) and are associated with excessive telomere attrition. Previously, in a cohort of patients with MDS, pathogenic germ line variants of telomerase genes were very extremely rare.Recently a patient with bone marrow failure and liver cirrhosis presented with a biallelic CTC1 gene mutation. CTC1 is a member of the CTC complex, located on Chr 17p13.1, and critical for telomere replication. GL alterations of this gene were found to cause inherited disease, including Coats plus (CP), dyskeratosis congenital (DC) and cerebroretinal microangiopathy with calcifications and cysts (CRMCC) in a compound heterozygous manner. Our patient (age 28) had compound heterozygous CTC1 germline mutations (p.Lys242Leufs*41 and p.Cys985del) resulting in early childhood presentation of DC, subsequent severe AA at the age of 19, and a significant shortening of telomeres. Both parents as confirmed CTC1 variant carriers showed normal blood counts.Based on this index case and literature reports, manifest CTC1 diseases follow a recessive trait, however, but it is possible that heterozygous carriers may indeed have also an increased, albeit attenuated risk of BMF leading to a later manifestation or incomplete penetrance. To test this possible scenario we screened a cohort of acquired BMF (n=538) with AA/PNH (172), MDS/AML (n=366), with deep NGS of all coding regions of CTC1. In total, we identified 10 heterozygous CTC1 variants in 10 unrelated patients (8 AA/PNH and 2 MDS); 4/10 variants (1 stop gain R1202X and 3 frameshift deletions D405fs, P999fs, E454fs) were fulfilled the criteria of Tier-1 lesions and were found in AA/PNH patients (4/172, 2.3%), The remaining 6 missense variants were of uncertain significance or likely benign(Tier-2), 2 of which (H1092G and E1136K) were found in a compound heterozygous configuration in a AA/PNH patient. K438N, as a novel missense variant, was recurrently present in 2 MDS pts. Given the expected frequency of the CTC1 variants found in controls (104/33370, 0.3%), CTC1 variants appear to be enriched in AA/PNH subgroup (p<0.001). Of note is that none of the carriers of pathogenic CTC1 mutations showed any physical signs of inherited congenital BMF syndromes or any family history of leukemia, BMF and any other cancers. Interestingly, patients with sAA/PNH syndrome and biallelic CTC1 variant eventually evolved to MDS, while the other monoallelic CTC1 carriers showed stable disease and responsed to immunosuppression. Flow cytometric telomere length measurement (adjusted for age) showed a markedly shortened telomere in the index case, as well as 1 SAA case carrying biallelic CTC1 variants and 1 AA case with co-concurrent POT1 and CTC1 variants when compared with age matched controls. A significant difference was seen when comparing telomere length between CTC1 variants carriers and age-matched normal controls, while no difference was seen among CTC1 variants carriers, AA/PNH group without any variants.Because of the curious co-incidence of heterozygous CTC1 variants and AA/PNH, we further analyzed this subgroup for the presence of other telomerase gene mutations, 11/172 Tier-1 variants, while 6 Tier-1 GLVs detected in MDS. Most frequent SNVs were found in POT1 with 5/172 (3%) in AA/PNH and 3/366 (0.8%) in MDS/AML. Notably, in one AA/PNH patient POT1 stop gain variant (Q364X) was co-concurrent with CTC1 heterozygous frame shift deletion (P999fs). The enrichment of variants in TELO-related genes in AA/PNH subgroup was found in comparison to MDS/AML (p<.01) and ExAC database controls (p<.01). Further clinical phenotype analysis indicated that 3 AA/PNH cases harboring POT1, TINF2 and TERT Tier-1 variants had family history of cancer. Family history of cancer was also found in a MDS patient with a TINF2 variant.In sum, our results indicate that heterozygous CTC1 variants were associated with otherwise typical AA with clonal outgrowth of PNH clone and the presence of this variant does not seem to preclude response to immunosuppression. DisclosuresMaciejewski:Ra Pharmaceuticals, Inc: Consultancy; Ra Pharmaceuticals, Inc: Consultancy; Apellis Pharmaceuticals: Consultancy; Apellis Pharmaceuticals: Consultancy; Alexion Pharmaceuticals, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Alexion Pharmaceuticals, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Clinical implications of telomere dysfunction in lung fibrosis.

Telomere attrition has been proposed as one of the aging hallmarks in pulmonary fibrosis. Telomere shortening and telomerase gene mutations have been widely evaluated in recent years. Reduced telomere length may be identified in a quarter of patients with sporadic idiopathic pulmonary fibrosis (IPF) and half of those cases with family aggregation. However, telomere studies have not transferred from the research field to the clinic. This review is focused on our current understanding of the pathogenic implication of telomere dysfunction in lung fibrosis and its relevance in the clinical setting. The most prevalent clinical expression of telomere dysfunction is IPF. Disease onset is usually seen at a younger age and family aggregation is frequently present. Short telomere syndrome is associated in a minority of cases and includes premature hair greying, bone marrow failure and liver cirrhosis. However, patients often present with some extrapulmonary associated telomeric features and related comorbidities that may help to suspect telomere defects. Telomere shortening confers a poor prognosis and reduced lung-transplant free survival time in IPF and other nonidiopathic pulmonary fibrotic entities. Telomere dysfunction associates some common clinical features that could modify patient management in pulmonary fibrosis.

Diagnostic utility of telomere length testing in a hospital-based setting

Telomere length (TL) predicts the onset of cellular senescence in vitro but the diagnostic utility of TL measurement in clinical settings is not fully known. We tested the value of TL measurement by flow cytometry and FISH (flowFISH) in patients with mutations in telomerase and telomere maintenance genes. TL had a discrete and reproducible normal range with definable upper and lower boundaries. While TL above the 50th age-adjusted percentile had a 100% negative predictive value for clinically relevant mutations, the lower threshold in mutation carriers was age-dependent, and adult mutation carriers often overlapped with the lowest decile of controls. The extent of telomere shortening correlated with the age at diagnosis as well as the short telomere syndrome phenotype. Extremely short TL caused bone marrow failure and immunodeficiency in children and young adults, while milder defects manifested as pulmonary fibrosis-emphysema in adults. We prospectively examined whether TL altered treatment decisions for newly diagnosed idiopathic bone marrow failure patients and found abnormally short TL enriched for patients with mutations in some inherited bone marrow failure genes, such as RUNX1, in addition to telomerase and telomere maintenance genes. The result was actionable, altering the choice of treatment regimen and/or hematopoietic stem cell donor in one-fourth of the cases (9 of 38, 24%). We conclude that TL measurement by flowFISH, when used for targeted clinical indications and in limited settings, can influence treatment decisions in ways that improve outcome.

Fanconi Anemia germline variants as susceptibility factors in aplastic anemia, MDS and AML.

Using next generation sequencing we have systematically analyzed a large cohort of 489 patients with bone marrow failure (BMF), including myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), aplastic anemia (AA), and related conditions for the presence of germline (GL) alterations in Fanconi Anemia (FA) and telomerase genes. We have detected an increased frequency of heterozygous FA gene mutations in MDS and to lesser degree in AML suggesting that the presence of one normal allele may not be completely protective and indeed heterozygous FA lesions may have a long latency period before hematologic manifestation. In contrast, GL telomerase gene mutations were not associated with increased disease risk. When compared to large control cohorts, we have not detected an increased frequency of damaging variants among telomerase complex genes, including those previously believed to be involved in the pathogenesis of AA. Our results may suggest that while low penetrance and delayed disease onset can confound identification of genetic predisposition factors, GL FA alterations can be also associated with MDS.

Telomerase and the Genetics of Emphysema Susceptibility. Implications for Pathogenesis Paradigms and Patient Care.

In the past five decades, alpha-1 antitrypsin deficiency has been the only known genetic cause of emphysema, yet it explains the genetics in only 1-2% of severe cases. Recently, mutations in telomerase genes were found to induce susceptibility to young-onset, severe, and familial emphysema at a frequency comparable to that of alpha-1 antitrypsin deficiency. Telomerase mutation carriers with emphysema report a family history of idiopathic pulmonary fibrosis, and both lung phenotypes show autosomal dominant inheritance within families. The data so far point to a strong gene-environment interaction that determines the lung disease type. In never-smokers, pulmonary fibrosis predominates, while smokers, especially females, are at risk for developing emphysema alone or in combination with pulmonary fibrosis. The telomere-mediated emphysema phenotype appears to have clinically recognizable features that are distinct from alpha-1 antitrypsin deficiency, and patients are prone to developing short telomere syndrome comorbidities that influence clinical outcomes. In animal models, telomere dysfunction causes alveolar epithelial stem cell senescence, which is sufficient to drive lung remodeling and recruit inflammation. Here, we review the implications of these discoveries for understanding emphysema biology as well as for patient care.

The role of Endoplasmic Reticulum (ER) stress in pulmonary fibrosis

AbstractThe activation of Endoplasmic Reticulum (ER) stress and Unfolded Protein Response (UPR) was first observed in patients with familial interstitial pneumonia (FIP) carrying mutations in the C-terminal BRICHOS domain of surfactant protein C (SFTPC). Here, aggresome formation and severe ER stress was demonstrated in type-II alveolar epithelial cells (AECII), which specifically express this very hydrophobic surfactant protein. In subsequent studies, FIP-patients with mutations in the gene encoding surfactant protein A2 (SFTPA2) were discovered, whose overexpression in epithelial cells in vitro also resulted in significant induction of ER stress. Moreover, prominent ER stress in AECII was also observed in FIP-patients not carrying the SFTPC/SFTPA2 mutations, as well as in patients with the more common sporadic forms of IP. Additionally, cases of adult-onset FIP with mutations in Telomerase genes and other telomereassociated components were reported. These mutations were associated with telomere shortening, which is a potential cause for triggering a persistent DNA damage response and replicative senescence in affected cells. Moreover, shortened telomeres were observed directly in the AECII of FIP-patients, and even sporadic IP cases, in the absence of any gene mutations. Here, we try to figure out the possible origins of ER stress in sporadic IP cases and non-SFTPC/SFTPA2-associated FIP.

Extrahematopoietic Manifestations of Telomere Syndromes

Abnormally short telomeres give rise to a group of premature aging, cancer-prone disorders known as the telomere syndromes. They are caused by germline mutations in telomerase and telomere genes. Although bone marrow failure was one of the first complications to be described in dyskeratosis congenita, there is increasing appreciation that this classic presentation is rare. Extra-hematopoietic telomere-mediated disease is frequently the first and predominant presentation in adults and leads to significant morbidity and mortality in patients with bone marrow failure (BMF), especially after bone marrow transplantation. It shows stereotypic manifestations that are age-dependent. Enterocolitis can precede the onset of BMF in infants with Hoyeraal-Hreidarsson syndrome, and it represents an intestinal epithelial defect that progresses in the setting of immunodeficiency. In adults with familial lung disease, idiopathic pulmonary fibrosis and emphysema are the predominant manifestations. These patients show variable degrees of BMF and are at risk for clonal abnormalities. In the lung transplant setting, adult telomere syndrome patients have an increased risk of complications due to immunosuppressive medications which challenge their reserves in the bone marrow, intestinal tract and elsewhere. Liver disease, often manifesting as hepatopulmonary syndrome, causes organ failure in approximately 10% of cases. The molecular mechanisms underlying telomere-mediated disease outside the bone marrow likely involve stem cell failure. For example, in the lung, alveolar stem cell senescence is sufficient to drive remodeling, inflammation, and susceptibility to injury, which are hallmark features of pulmonary fibrosis and emphysema. The stem cell failure mechanism has implications for approaching treatment in these lung disorders which have heretofore been considered mediated by inflammation. This session will present evolving scientific evidence that sheds light on the mechanisms and natural history of telomere syndromes. Considerations in the diagnostic work-up of suspected cases and the implications for patient care will be reviewed. Disclosures No relevant conflicts of interest to declare.

Hepatopulmonary Syndrome Is a Frequent Cause of Dyspnea in the Short Telomere Disorders

Telomere syndromes have their most common manifestation in idiopathic pulmonary fibrosis and emphysema. The short telomere defect in these patients may manifest systemically as bone marrow failure and liver disease. We sought to understand the causes of dyspnea in telomerase and telomere gene mutation carriers who have no parenchymal lung disease. Clinical and pathologic data were reviewed as part of a Johns Hopkins-based natural history study of short telomere syndromes including dyskeratosis congenita. Hepatopulmonary syndrome (HPS) was diagnosed in nine of 42 cases (21%). Their age at presentation was significantly younger than that of cases initially presenting with pulmonary fibrosis and emphysema (median, 25 years vs 55 years; P < .001). Cases had evidence of intra- and extrapulmonary arteriovascular malformations that caused shunt physiology. Nodular regenerative hyperplasia was the most frequent histopathologic abnormality, and it was seen in the absence of cirrhosis. Dyspnea and portal hypertension were progressive, and the median time to death or liver transplantation was 6 years (range, 4-10 years; n = 6). In cases that underwent liver transplantation, dyspnea and hypoxia improved, but pulmonary fibrosis subsequently developed. This report identifies HPS as a frequent cause of dyspnea in telomerase and telomere gene mutation carriers. While it usually precedes the development of parenchymal lung disease, HPS may also co-occur with pulmonary fibrosis and emphysema. Recognizing this genetic diagnosis is critical for management, especially in the lung and liver transplantation setting.

Association between telomere length and survival in patients with idiopathic pulmonary fibrosis

Short telomere is a crucial risk factor for idiopathic pulmonary fibrosis (IPF). However, little is known about the association between baseline telomere length and survival in IPF. We aimed to determine whether telomere length is associated with survival of IPF. Leukocyte telomere lengths were measured by quantitative polymerase chain reaction in IPF patients at the time of the initial enrolment assessment in Nanjing Drum Tower Hospital Affiliated to Medical School of Nanjing University. The primary endpoint was the survival of the IPF patients since their initial enrolment assessment. Ninety-four IPF patients were enrolled between 1 January 2012 and 30 June 2014. The mean age-adjusted telomere length of IPF patients (0.85 ± 0.60) was significantly shorter than age-matched controls (1.15 ± 0.60, P = 0.001). During the follow-up period, 43 IPF patients died. The mean age-adjusted telomere length of the non-survivors (0.61 ± 0.53) was significantly shorter than that of the survivors (1.03 ± 0.59, P = 0.005). The association between telomere length (hazard ratio (HR) 0.470 (95% confidence interval (CI): 0.25-0. 89); P = 0·019) and survival in patients with IPF was independent of age, sex, forced vital capacity or diffusing capacity of carbon monoxide. After excluding the six patients with telomerase gene mutations, telomere length (HR 0.46 (95% CI: 0.24-0.88); P = 0·018) remained an independent predictor of survival time in patients with IPF. Short telomere length is independently associated with worse survival in IPF. Future research should focus on the molecular mechanism underlying the shortening of telomere length in IPF.

Telomerase gene mutations and telomere length shortening in patients with idiopathic pulmonary fibrosis in a Chinese population.

Idiopathic pulmonary fibrosis (IPF) is an age-related disease and the most common manifestation of telomere-mediated disorders. We collected detailed medical histories and DNA samples from 100 IPF patients seen at Nanjing Drum Tower Hospital Affiliated to Medical School of Nanjing University. All patients had sporadic IPF, with no family history reported. We screened all patients for telomerase reverse transcriptase (TERT) and telomerase RNA component (TERC) variants, and measured their telomere lengths in lymphocytes. Six novel telomerase gene mutations were identified in six IPF patients enrolled in the studies. They were two heterozygous mutations in TERC (257 G>A and 108 C>T) and four in TERT (R622H, T644M, V777L and F1032I). IPF patients with TERT/TERC mutations had significant thrombocytopaenia (160.167 ± 28.089 × 10(9)) compared with the non-mutation groups (191.018 ± 71.187 × 10(9), P = 0.047). All IPF patients with TERT/TERC mutations had shortened telomeres (0.656 ± 0.125) compared with the patients lacking TERT/TERC mutations (1.080 ± 0.6819, P = 0.0184). IPF patients lacking TERT or TERC mutations (1.080 ± 0.6819) had significantly shorter telomeres compared with age-matched healthy controls (1.244 ± 0.5890, P = 0.0355). Six novel mutations in the telomerase genes were identified for the first time in individuals diagnosed with sporadic IPF in a Chinese Han population. Shorter telomeres and mild thrombocytopaenia could be clues to association with telomerase gene mutation and sporadic IPF.