Telomere Syndromes Research Articles

S2693 Outcome of Hepatitis C Virus-Positive Liver Transplantation for Telomere-Mediated HPS-Noncirrhotic Portal Hypertension After Bone Marrow Transplantation: A Case Report

INTRODUCTION: Short telomere syndromes are disorders caused by germline mutations in genes regulating telomere maintenance. Their phenotypes and severity vary and depend on the extent of telomere shortening. Dyskeratosis congenita (DC) is a prototypic short telomere syndrome, characterized by bone marrow failure, liver disease (noncirrhotic portal hypertension, cryptogenic cirrhosis), pulmonary fibrosis and an increased risk of malignancy. With contemporary hematopoietic stem cell transplantation (HSCT) regimens, non-cirrhotic portal hypertension with hepatopulmonary syndrome (HPS) is the most common morbidity. We describe successful HCV-positive liver transplantation (LT) for telomere-mediated noncirrhotic portal hypertension with HPS after HSCT. CASE DESCRIPTION/METHODS: A 27-year-old female with DC complicated by noncirrhotic portal hypertension and HPS underwent LT at age 25, from a 23-year-old, HCV-positive, female donor. The recipient was diagnosed with bone marrow failure and DC at age 17. At that time, telomere length was below the 1st age-adjusted percentile, but she had no identifiable mutation. She underwent a non-myeloablative HSCT at age 19. Three years later, she presented with progressive dyspnea and was found to have stigmata of portal hypertension and intrapulmonary shunt. A trans-jugular liver biopsy confirmed the absence of significant fibrosis with a hepatic venous pressure gradient of 10 mmHg. Her dyspnea continued to progress with minimal evidence of parenchymal pulmonary fibrosis but worsening HPS. She was on 10 L oxygen prior to LT with room air PO2 55 mmHg, qualifying for UNOS upgrade to MELD 29. Liver explant pathology revealed focal parenchymal nodularity and absence of significant fibrosis. She had a prolonged recovery due to respiratory failure and malnutrition, which she recovered from and completely weaned off oxygen four months post-LT. She was successfully treated for HCV post-LT. She had recurrent low-level CMV viremia and presumed mild graft rejection episode. Sixteen months post-LT, she continues to be on room air with stable lung and liver graft function. DISCUSSION: The natural history of short telomere syndromes is marked by progressive noncirrhotic portal hypertension with HPS, a frequent long-term complication after HSCT. We report a successful LT and reversal of hypoxemia after an HCV-positive LT in a patient with DC. Sequential transplant may be feasible option for post-HSCT patients who develop end-stage liver disease.

Telomere Dysfunction Activates p53 and Represses HNF4α Expression Leading to Impaired Human Hepatocyte Development and Function.

Background and AimsTelomere attrition is a major risk factor for end‐stage liver disease. Due to a lack of adequate models and intrinsic difficulties in studying telomerase in physiologically relevant cells, the molecular mechanisms responsible for liver disease in patients with telomere syndromes remain elusive. To circumvent that, we used genome editing to generate isogenic human embryonic stem cells (hESCs) harboring clinically relevant mutations in telomerase and subjected them to an in vitro, stage‐specific hepatocyte differentiation protocol that resembles hepatocyte development in vivo.Approach and ResultsUsing this platform, we observed that while telomerase is highly expressed in hESCs, it is quickly silenced, specifically due to telomerase reverse transcriptase component (TERT) down‐regulation, immediately after endoderm differentiation and completely absent in in vitro–derived hepatocytes, similar to what is observed in human primary hepatocytes. While endoderm derivation is not impacted by telomere shortening, progressive telomere dysfunction impaired hepatic endoderm formation. Consequently, hepatocyte derivation, as measured by expression of specific hepatic markers as well by albumin expression and secretion, is severely compromised in telomerase mutant cells with short telomeres. Interestingly, this phenotype was not caused by cell death induction or senescence. Rather, telomere shortening prevents the up‐regulation and activation of human hepatocyte nuclear factor 4 alpha (HNF4α) in a p53‐dependent manner. Both reactivation of telomerase and silencing of p53 rescued hepatocyte formation in telomerase mutants. Likewise, the conditional expression (doxycycline‐controlled) of HNF4α, even in cells that retained short telomeres, accrued DNA damage, and exhibited p53 stabilization, successfully restored hepatocyte formation from hESCS.ConclusionsOur data show that telomere dysfunction acts as a major regulator of HNF4α during hepatocyte development, pointing to a target in the treatment of liver disease in telomere‐syndrome patients.

Synonymous Mutation in DKC1 Causes Telomerase RNA Insufficiency Manifesting as Familial Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is the most common of short telomere phenotypes. Familial clustering of IPF is common, but the genetic basis remains unknown in more than one-half of cases. We identified a 65-year-old man with familial IPF, short telomere length, and low telomerase RNA levels. He was diagnosed with a short telomere syndrome after developing hematologic complications post-lung transplantation, but no mutations were identified in a clinical testing pipeline. What is the molecular basis underlying the familial IPF and low telomerase RNA levels in this patient? We analyzed whole-genome sequence data and performed functional molecular studies on cells derived from the patient and his family. We identified a previously unreported synonymous variant c.942G>A p.K314K in DKC1, the gene encoding the dyskerin ribonucleoprotein, which is required for telomerase RNA biogenesis. The mutation created a competing de novo exonic splicing enhancer, and the misspliced product was degraded by nonsense-mediated decay causing an overall dyskerin deficiency in mutation carriers. In silico tools identified other rare silent DKC1 variants that warrant functional evaluation if found in patients with short telomere-mediated disease. Our data point to silent mutation in telomere maintenance genes as a mechanism of familial pulmonary fibrosis. In contrast to DKC1 missense mutations, which primarily manifest in children as dyskeratosis congenita, hypomorphic mutations affecting dyskerin levels likely have a predilection to presenting in adults as pulmonary fibrosis.

Metabolic Syndrome, telomere length and Aging, Review of literature

Metabolic syndrome is reportedly one of the key health concerns worldwide. It is defined as a group of conditions including hypertension, dysglycemia, and abdominal obesity. The wear and tear of telomeres is known to be a major incident not only in mammalian aging, but also in distressed nutrient sensing, which may contribute to a number of metabolic dysfunctions. The metabolic syndrome was linked to the growing prevalence of obesity, which is at rise invariably in all age groups including elderly. The existing literature review focuses on the relationship of shorting of telomere and metabolic syndrome. As the shortening of telomeres influence cellular senescence and eventual stoppage of cell division.

Short Telomeres: Cause and Consequence in Liver Disease.

Short telomere syndrome is a genetically inherited syndrome resulting in premature telomere shortening. This premature shortening of telomeres can result in hematologic, pulmonary, vascular, gastrointestinal, and hepatic manifestations of disease. Identifying patients with short telomere syndrome can be a clinical challenge due to the multitude of potential manifestations and lack of widely available diagnostic tests. In this review, we will highlight hepatic manifestations of short telomere syndrome with a focus on diagnosis, testing, and potential treatments.

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.

Pulmonary Fibrosis and a TERT Founder Mutation With a Latency Period of 300 Years

Germline mutations in the gene encoding TERT cause haploinsufficiency with subsequent telomere shortening. TERT mutations are associated with short telomere syndromes, such as pulmonary fibrosis (PF), which is often the first manifestation of a short telomere syndrome. Telomere length is heritable, and progeny of telomerase mutation carriers are known to have shorter telomeres. In families with TERT mutations, genetic anticipation, the earlier onset of symptoms with successive generation, is described. Little is known on the number of generations that may pass before disease occurs in families with a TERT mutation. The objective of this study was to determine classification and origin of the new TERT c.2005T mutation from population genetics and genealogic data and disease history of affected families. The TERT gene of 240 patients with familial PF was screened for mutations. Additionally, 1,015 patients with PF, 1,237 patients with an interstitial lung disease (ILD) without PF, and 529 healthy control subjects were genotyped for the TERT c.2005C>T mutation. Genealogic research was performed on all patients who carried the TERT c.2005T mutation. We detected the TERT c.2005T (p.Arg669Trp) mutation in 13 out of 1,255 patients with PF vs none of the patients with ILD without PF and the healthy control subjects. Genealogic research connected four of the TERT c.2005T mutation carriers to a common ancestor who lived seven generations back, spanning a period of 300 years. The TERT c.2005T mutation is a pathogenic mutation and associates with PF. This study learns that a latency period of > 300 years may pass before the cumulative effect of telomere shortening eventually leads to PF. This finding underlines the complexity of the clinical interpretation of TERT mutations because, not the presence of the mutation, but the result of genetic anticipation, is associated with disease. Therefore, multidisciplinary discussion between pulmonary physicians, clinical geneticists, and genetic laboratory experts is recommended.

Successful liver transplantation in short telomere syndromes without bone marrow failure due to DKC1 mutation

Short telomere syndromes are a heterogenous spectrum of disorders leading to premature cellular aging. These may involve bone marrow failure, adult-onset idiopathic pulmonary fibrosis, and liver disease, and classical entities such as dyskeratosis congenita. We report a patient who presented with common variable immunodeficiency at 3years of age and autoimmune cytopenias at 8years of age. He was found to have short telomeres, and genetic testing confirmed a hemizygous mutation NM_001363.4: c.-142C>G in DKC1 gene. He subsequently developed cirrhosis with severe portal hypertension and hepatopulmonary syndrome, prompting liver transplantation at 11years of age. He remains well 10years after transplant with no progression of bone marrow failure or progressive lung disease. In conclusion, short telomere syndromes should be considered as a potential cause of pediatric liver disease of unknown etiology, and in severe cases, isolated liver transplantation may be both appropriate and successful.

Short telomere syndromes, premature ageing syndromes, and biological ageing.

Short telomere syndromes, premature ageing syndromes, and biological ageing.

Clinical Utility of Telomere Length-Directed Genomic Assessment in Patients with Short Telomere Syndromes

Introduction: Short telomere syndromes (STS) are accelerated aging syndromes affecting hematopoietic, pulmonary, hepatobiliary and/or immunological systems. Clinical assessment of age-appropriate telomere length (TL) is performed using flow cytometry & fluorescence in-situ hybridization (flowFISH). Screening for germline variants in STS-related genes is guided by flowFISH-determined centile categories of TL, with screening recommended for TL <1st centile or 1-10th centile in lymphocytes (L) or granulocytes (G). However, the utility of genetic testing for patients with TL >10th centile and integration of clinical phenotype with flowFISH data in predictive algorithms is currently unclear. Methods: FlowFISH testing was done at reference laboratories in Vancouver (Repeat Diagnostics; Canada) & Johns Hopkins University (JHU, USA). Salient clinical features were pre-determined as, personal history of premature hair greying (onset at age < 30 years), idiopathic pulmonary fibrosis (IPF) or IPF/emphysema overlap (in smokers), cryptogenic cirrhosis or NRH, unexplained cytopenias &/or immunodeficiency, & family history of the above (in >1 1st or 2nd degree relatives). Clinical likelihood score (CLS) was assigned as low (1), intermediate (int, 2) or high (>2), based on the number of aforementioned clinical features present prior to flowFISH testing. Genetic testing was performed using either an in-house or commercial bone marrow failure-specific next generation sequencing (NGS) panel or whole exome sequencing (WES), and data for known variants affecting telomerase or telomeric function (TERT, TERC, DKC1, TINF2, NHP2, NOP10, TCAB1, NAF1, & RTEL1) was recorded. Results: One hundred forty-nine patients at our institution underwent TL assessment at Repeat diagnostics (n=38) and JHU (n=111) laboratories, respectively. Median age was 56 (range: 7-79) years; 88 (59%) being males. Significant family history was present in 40 (27%) patients, while premature greying of hair was present in 13 (9%) patients. Organ-specific clinical features included unexplained cytopenias (n=89, 60%) IPF (n=71, 48%), cryptogenic cirrhosis or NRH (n=21, 14%), & unexplained immunodeficiency (n=14, 9%). CLS stratification included low (n=74, 50%), int (n=54, 36%), & high (n=21, 14%), with higher CLS significantly correlating with lower delta TL for L (p=0.0005) but not G (p=0.3). Genetic testing was performed in 51 (35%) patients (NGS-51, WES-1) among which 13 (26%) patients had a telomere-associated variant; 5 (10%) pathogenic (pv, all TERT). CLS alone was unable to predict likelihood of finding a telomere-associated variant (p=0.4). Based on age-appropriate centile categorization of L & G TL (information for both available in 134 patients), patients were stratified into six groups (table 1). TL <1st centile in L: This group was further divided into two groups; TL<1st centile in both L & G [A1, n=7, CLS low-3 (43%), int-2 (29%), & high-2 (29%)] and TL <1st centile in L and 1-50th centile in G (A2, n=2, CLS low & high) patients. Among the 4 (57%) patients who underwent genetic (NGS-3, WES-1) testing, 3 (75%) had TERTpv in A1 subgroup and 1 A2 subgroup patient had a VUS in TERT.TL <1st centile in G, 1-10th centile in L (n=18): This group included 9 (50%) low, 8 (44%) int and 1 (6) high CLS patients, of which only 1 of 8 NGS-tested patients had TERTpv.TL 1-10th centile in L or G: This group was divided into; 1-10th centile in both L & G [C1, n=28, CLS low-3 (11%), int-14 (50%), high-11(39%)] of whom 8 (22%) underwent NGS with no pathogenic variants but 3 VUS in RTEL1, NAF1 & PARN genes, and 1-10th centile in L, >1-90th centile in G [C2, n=36, CLS low-19 (53%), 16 (44%), 1 (3%)] of whom 8 (22%) underwent NGS with 1 TERTpv and 2 VUS in TINF2TL >10th centile in L & 1-90th centile in G (n=43, 32%): CLS stratification in this group included 27 (63%) low, 12 (28%) int, 4 (9%) high. NGS testing was done in 13 (30%) patients [CLS low-9(69%), int 2(15%), high 2 (15%)], of whom only 2 (15%) had VUS in TINF2 and TERT gene, but no pathogenic variants (figure 1). Conclusion: Our study demonstrates the importance of using a flowFISH assay based predictive algorithm to screen patients with suspected STS for telomere-related genetic alternations, in comparison to a clinical likelihood score. We also demonstrate a limited role for genetic testing in patients with lymphocyte TL >10th centile, regardless of the clinical likelihood score. Disclosures Patnaik: Stem Line Pharmaceuticals.: Membership on an entity's Board of Directors or advisory committees.

Survival Outcomes Following Allogeneic Stem Cell Transplantation for Inherited Bone Marrow Failure and Myeloid Germline Predisposition Syndromes

Introduction: Allogeneic stem cell transplant (HCT) is the only potential curative option for patients with inherited marrow failure (iBMF) and myeloid germline predisposition syndromes (GPD). HCT outcomes are influenced by inherent disease specific-nuances such as alkylating agent and radio-sensitivity, immune deregulation, and higher risks for graft failure and GVHD; factors contributing to transplant related mortality (TRM) and morbidity. We carried out this retrospective study to assess survival outcomes and long term complications (LTC) in patients with IBMF and GPD that underwent HCT. Patients and methods: We queried our institutional database and identified patients with iBMF and GPD as defined by the 2016 WHO classification. These included Fanconi anemia (FA), short telomere syndromes (STS), Diamond-Blackfan anemia (DBA), GATA2 and RUNX1 haploinsufficiency, congenital amegakaryocytic thrombocytopenia (CAMT), deficiency of adenosine deaminase 2 (DADA2), among others. Patients with acquired causes of BMF were excluded. Statistical analyses were performed using SAS (JMP v14.1). Results: Twenty eight patients, median age 10 years (1 month-63 years), 46% males, were included in the study (table 1). Fanconi anemia Seven (25%) patients with FA underwent HCT, 5 (71%) without myeloid transformation and 2 after transformation to MDS/AML. Five (71%) patients received a RIC, 4 (57%) prior to transformation. At a median follow up (FU) of 126 m, the median OS was 194 m (95% CI 34m; NR) and 10 year survival was 64%. Grade 1 aGVHD was seen in four (57%) and 3 (42%) developed mild cGVHD, while 1 developed a donor derived AML (sibling not tested for FA). LTC included second primary malignancy (SPM) - squamous cell cancer (SCC) of skin and muscle invasive bladder cancer (MIBC) in 1(14%) and SCC of head/neck and anogenital region in 3 patients (43%), psychosocial complications (PS) in 6(85%), premature ovarian failure (POF) in 3(43%), and avascular necrosis (AVN) in 4(57%) patients. Short Telomere Syndromes (STS) Seven patients with STS underwent HCT, 2 (28%) after transformation to MDS. Five (71%) received RIC, including both the transformed patients. At a median FU of 67m, median OS was NR (95% CI 2m; NR) and 5 year survival was 47%. One (14%) patient developed grade 2 aGVHD and mild cGVHD of skin. Three (43%) developed SPM - skin cancers in 2 and MIBC in 1. PS was noted in 1(15%), and AVN in 3(43%). Three (43%) patients had concomitant mild IPF/restrictive lung disease. GATA2 haploinsufficiency : Seven patients with GATA2 haploinsufficiency underwent HCT; 2(28.5%) after transformation to MDS and 3(43%) to AML, of which 2(40%) received MAC. At a median FU of 57m, median OS was NR (95% CI 7m; NR) and 5 year survival was 71%. Three (50%) developed grade 2 aGVHD of skin and GI tract and 2(33%) developed mild cGVHD. LTC include PTLD, AVN and POF in 1 patient each. Ribosomopathies : One patient (13y) with DBA underwent RIC HCT and developed grade 2 aGVHD, secondary iron overload, and died at 10 months due to severe fungal infection. Others : Identical twins with CAMT underwent HCT (at 4y and 5y) from the same unrelated donor and at last FU (74m and 87m, respectively) remain 100% donor without GVHD. Two children with primary immunodeficiency and marrow failure underwent HCT (at 2y and 7y), one after transformation to MDS. The non-transformed patient is currently alive (120m), while the patient with transformation died 1month after HCT from disseminated cytomegalovirus infection. One patient with germline RUNX1 deletion developed CMML and underwent a RIC HCT and is alive at a FU of 4 months, with no GVHD. One patient with DADA2 (n=1) underwent RIC HCT without LTC. Due to the smaller cohort size, we compared OS in transformed and non-transformed patients for the IBMF and GATA2 patients only (n=24, 9 with transformation) (figure1). At a median FU of 74m, the median OS of transformed vs non-transformed patients was 108m(95% CI 1;108m) and 163m(95% CI 67m; NR), respectively (p=0.033). Conclusions: Our study demonstrates that HCT remains an important intervention for IBMF and GPD, with the maximum impact being gained prior to transformation. While only mild chronic GVHD was noted (37%), inherent syndromic issues resulted in a high rate of SPM (FA/STS) and organ failure (STS- IPF). Notably, one FA patient who received an MRD HCT developed donor derived AML, underlining the importance of genetic screening in asymptomatic related individuals. Disclosures Kenderian: Lentigen: Research Funding; Kite/Gilead: Research Funding; Morphosys: Research Funding; Humanigen: Other: Scientific advisory board , Patents & Royalties, Research Funding; Novartis: Patents & Royalties, Research Funding; Tolero: Research Funding. Patnaik:Stem Line Pharmaceuticals.: Membership on an entity's Board of Directors or advisory committees.

INCREASED SUSCEPTIBILITY TO HERPESVIRUS COMPLICATIONS IN PULMONARY FIBROSIS LUNG TRANSPLANT RECIPIENTS WITH SHORT TELOMERES

SESSION TITLE: Late Breaking Pulmonary Fibrosis SESSION TYPE: Original Investigations PRESENTED ON: 10/22/2019 08:45 AM - 09:45 AM PURPOSE: Idiopathic Pulmonary Fibrosis (IPF) is the leading indication for lung transplantation in North America, however transplant survival rates in this population lag behind all other end-stage lung diseases. Herpesvirus infectious complications are common causes of morbidity and mortality among lung transplant recipients (LTRs). We recently demonstrated that a high percentage of IPF lung transplant recipients (IPF-LTRs) have short lymphocyte telomere length (short TL) using flow cytometry and fluorescence in situ hybridization. Cytomegalovirus (CMV) infection continues to be one of the most common opportunistic infections in LTRs and is associated with chronic lung allograft dysfunction (CLAD). Epstein Barr virus (EBV)-associated post-transplant lymphoproliferative disorder (PTLD) is a herpesvirus transplant complication that is associated with significant mortality. METHODS: We performed retrospective outcomes analyses combined with genetic analyses in a single institution LTR cohort. RESULTS: We have shown that IPF-LTRs with short TL have increased susceptibility to CMV viremia and other CMV complications post-transplant, compared to age-matched non-IPF-LTRs (P < 0.01). In addition, we find that IPF-LTRs with short TL demonstrate impaired CMV-specific T cell immunity compared to non-IPF-LTRs. We evaluated a cohort of 611 LTRs at our institution from 2010-2016 for EBV-associated post-transplant lymphoproliferative disorder (PTLD) and found 28 cases of PTLD (4.6% incidence). Of these, 12/28 patients (43%) were IPF-LTRs and IPF was a risk factor associated with PTLD (Odds ratio: 2.9; 95% CI: 1.2-6.9; P<0.02). Kaplan Meier analyses demonstrated a significant decreased freedom from EBV-associated PTLD among IPF-LTRs (P<0.02), as well as decreased survival with PTLD in IPF-LTRs with PTLD (P<0.05). In addition, EBV mismatch (donor+/recipient-), a known risk factor for PTLD, carried an increased risk (Odds ratio: 6.9; 95% CI 2.3-20.9; P<0.001), while other factors such as male sex or age (risk factors for IPF) were not associated with increase risk for PTLD. Using both targeted exome sequencing and whole genome sequencing approaches, we found genetic mutations in either telomere or telomere-maintenance genes associated with the short telomere syndrome among both the CMV cohort and IPF-LTRs with EBV-PTLD. CONCLUSIONS: Together, these data highlight a predominance of short TL among current IPF-LTRs, along with increased susceptibility to herpesvirus complications in IPF-LTRs as manifestations of the short telomere syndrome. The identification of IPF-LTRs at increased risk for herpesvirus complications using telomere length and genome sequencing, may allow the development of clinical strategies to mitigate these post-transplant complications. CLINICAL IMPLICATIONS: Short telomeres are common in IPF LTRs. Stratification of risk for CMV and EBV-PTLD can advance strategies to mitigate adverse clinical outcomes. DISCLOSURES: No relevant relationships by Jonathan Alder, source=Web Response No relevant relationships by Stefanie Hannan, source=Web Response No relevant relationships by Carlo Iasella, source=Web Response No relevant relationships by Ritchie Koshy, source=Web Response No relevant relationships by John McDyer, source=Web Response No relevant relationships by Matthew Morrell, source=Web Response No relevant relationships by Seyed Mehdi Nouraie, source=Web Response No relevant relationships by Joseph Pilewski, source=Web Response No relevant relationships by Iulia Popescu, source=Web Response No relevant relationships by Pablo Sanchez, source=Web Response no disclosure on file for Fernanda Silveira; No relevant relationships by Spencer Winters, source=Web Response

ZCCHC8, the nuclear exosome targeting component, is mutated in familial pulmonary fibrosis and is required for telomerase RNA maturation

Short telomere syndromes manifest as familial idiopathic pulmonary fibrosis; they are the most common premature aging disorders. We used genome-wide linkage to identify heterozygous loss of function of ZCCHC8, a zinc-knuckle containing protein, as a cause of autosomal dominant pulmonary fibrosis. ZCCHC8 associated with TR and was required for telomerase function. In ZCCHC8 knockout cells and in mutation carriers, genomically extended telomerase RNA (TR) accumulated at the expense of mature TR, consistent with a role for ZCCHC8 in mediating TR 3' end targeting to the nuclear RNA exosome. We generated Zcchc8-null mice and found that heterozygotes, similar to human mutation carriers, had TR insufficiency but an otherwise preserved transcriptome. In contrast, Zcchc8-/- mice developed progressive and fatal neurodevelopmental pathology with features of a ciliopathy. The Zcchc8-/- brain transcriptome was highly dysregulated, showing accumulation and 3' end misprocessing of other low-abundance RNAs, including those encoding cilia components as well as the intronless replication-dependent histones. Our data identify a novel cause of human short telomere syndromes-familial pulmonary fibrosis and uncover nuclear exosome targeting as an essential 3' end maturation mechanism that vertebrate TR shares with replication-dependent histones.

Long telomeres and cancer risk: the price of cellular immortality

The distribution of telomere length in humans is broad, but it has finite upper and lower boundaries. Growing evidence shows that there are disease processes that are caused by both short and long telomere length extremes. The genetic basis of these short and long telomere syndromes may be linked to mutations in the same genes, such as the telomerase reverse transcriptase (TERT), but through differential effects on telomere length. Short telomere syndromes have a predominant degenerative phenotype marked by organ failure that most commonly manifests as pulmonary fibrosis and are associated with a relatively low cancer incidence. In contrast, insights from studies of cancer-prone families as well as genome-wide association studies (GWAS) have identified both rare and common variants that lengthen telomeres as being strongly associated with cancer risk. We have hypothesized that these cancers represent a long telomere syndrome that is associated with a high penetrance of cutaneous melanoma and chronic lymphocytic leukemia. In this Review, we will synthesize the clinical and human genetic observations with data from mouse models to define the role of telomeres in cancer etiology and biology.

Lung Transplantation for Familial Pulmonary Fibrosis

Purpose Up to 20% of idiopathic interstitial pneumonia (IIP) cases cluster in families, and familial pulmonary fibrosis (FPF) may require lung transplantation similar to sporadic idiopathic pulmonary fibrosis (IPF). However, transplant outcomes for FPF are not well characterized. We compared lung transplant for FPF versus IPF in a single center. Methods We identified all lung transplant recipients at UCLA between January 2006 and July 2017 with a UNOS lung diagnosis code of IIP: Idiopathic pulmonary fibrosis. After review of medical records and explant pathology, alternative diagnoses were excluded. Among the remaining cohort, we defined FPF as IIP with at least 1 reported first-degree relative with IIP, or those with a pathogenic variant identified on molecular genetic testing in a gene known to be associated with FPF. The remaining patients were considered IPF. The demographics, clinical parameters, and outcomes were compared between FPF and IPF groups. Results The final cohort included 288 patients, 37 (12.8%) FPF and 251 (87.2%) IPF. Demographic and baseline clinical parameters including laboratory tests were not significantly different between FPF and IPF groups. At 6-months post-transplant, FPF patients had lower WBC (4.1 vs. 5.1, p=0.02) and lower hemoglobin (11.5 vs 12.3, p=0.002). At 12-months, FPF patients had lower hemoglobin (11.5 vs 12.2, p=0.01). There was no significant difference in freedom from CLAD, CLAD free survival, or overall survival between FPF and IPF. Most FPF patients did not have genetic testing, but a subset of FPF patients with established short telomere syndrome (n=6) were more likely to develop severe neutropenia (50% vs 15.5%, p=0.02) and had worse survival (p=0.045) than patients transplanted for sporadic IPF. Conclusion Transplant for familial IPF has outcomes similar to sporadic IPF, but is associated with more cytopenia post-transplant. A subset of FPF with short telomere syndrome may have increased incidence of marrow failure and worse post-transplant survival than sporadic IPF.

Telomeres in Interstitial Lung Disease: The Short and the Long of It.

Telomeres are repetitive nucleotide sequences that cap linear chromosomes, thereby limiting progressive chromosomal shortening during cell replication. In conjunction with environmental factors, common single-nucleotide polymorphisms and rare and ultra-rare telomere-related mutations are associated with accelerated telomere shortening resulting in organ dysfunction, including interstitial lung disease (ILD). The most common telomere-related mutation-associated ILD is idiopathic pulmonary fibrosis (IPF). Up to one-third of individuals with familial IPF have shortened telomeres and/or carry a telomere-related mutation, and 1 in 10 individuals with sporadic IPF have telomere-related mutations. Regardless of ILD phenotype, individuals with short telomeres and/or known telomere-related mutations have more rapid disease progression and shorter lung transplant-free survival. Management should include initiation of antifibrotic agents for those with an IPF phenotype and early referral to a transplant center. Patients with ILD being considered for transplant should be screened for short telomeres if there is a significant family history of pulmonary fibrosis or evidence of extrapulmonary organ dysfunction associated with a short telomere syndrome. Post-transplant management of recipients with telomere-related mutations should include careful adjustment of immunosuppression regimens on the basis of bone marrow reserve. Data on the impact of shortened telomeres on post-transplant outcomes, however, remain mixed.

Short telomere syndromes cause a primary T cell immunodeficiency.

The mechanisms that drive T cell aging are not understood. We report that children and adult telomerase mutation carriers with short telomere length (TL) develop a T cell immunodeficiency that can manifest in the absence of bone marrow failure and causes life-threatening opportunistic infections. Mutation carriers shared T cell-aging phenotypes seen in adults 5 decades older, including depleted naive T cells, increased apoptosis, and restricted T cell repertoire. T cell receptor excision circles (TRECs) were also undetectable or low, suggesting that newborn screening may identify individuals with germline telomere maintenance defects. Telomerase-null mice with short TL showed defects throughout T cell development, including increased apoptosis of stimulated thymocytes, their intrathymic precursors, in addition to depleted hematopoietic reserves. When we examined the transcriptional programs of T cells from telomerase mutation carriers, we found they diverged from older adults with normal TL. Short telomere T cells upregulated DNA damage and intrinsic apoptosis pathways, while older adult T cells upregulated extrinsic apoptosis pathways and programmed cell death 1 (PD-1) expression. T cells from mice with short TL also showed an active DNA-damage response, in contrast with old WT mice, despite their shared propensity to apoptosis. Our data suggest there are TL-dependent and TL-independent mechanisms that differentially contribute to distinct molecular programs of T cell apoptosis with aging.

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.

AAV9-mediated telomerase activation does not accelerate tumorigenesis in the context of oncogenic K-Ras-induced lung cancer.

Short and dysfunctional telomeres are sufficient to induce a persistent DNA damage response at chromosome ends, which leads to the induction of senescence and/or apoptosis and to various age-related conditions, including a group of diseases known as “telomere syndromes”, which are provoked by extremely short telomeres owing to germline mutations in telomere genes. This opens the possibility of using telomerase activation as a potential therapeutic strategy to rescue short telomeres both in telomere syndromes and in age-related diseases, in this manner maintaining tissue homeostasis and ameliorating these diseases. In the past, we generated adeno-associated viral vectors carrying the telomerase gene (AAV9-Tert) and shown their therapeutic efficacy in mouse models of cardiac infarct, aplastic anemia, and pulmonary fibrosis. Although we did not observe increased cancer incidence as a consequence of Tert overexpression in any of those models, here we set to test the safety of AAV9-mediated Tert overexpression in the context of a cancer prone mouse model, owing to expression of oncogenic K-ras. As control, we also treated mice with AAV9 vectors carrying a catalytically inactive form of Tert, known to inhibit endogenous telomerase activity. We found that overexpression of Tert does not accelerate the onset or progression of lung carcinomas, even when in the setting of a p53-null background. These findings indicate that telomerase activation by using AAV9-mediated Tert gene therapy has no detectable cancer-prone effects in the context of oncogene-induced mouse tumors.

Clinical Correlates and Treatment Outcomes for Patients With Short Telomere Syndromes

Short telomere syndromes (STSs) are accelerated aging syndromes with multisystemic manifestations that present complex management challenges. In this article, we discuss a single-institution experience in diagnosing and managing patients with inherited STSs. In total, we identified 17 patients with short telomeres, defined by flow-fluorescence in-situ hybridization telomere lengths of less than first centile in granulocytes/lymphocytes OR the presence of a characteristic germline pathogenic variant in the context of a highly suggestive clinical phenotype. Genetic variations in the telomere complex were identified in 6 (35%) patients, with 4 being known pathogenic variants involving TERT (n=2), TERC (n=1), and DKC1 (n=1) genes, while 2 were variants of uncertain significance in TERT and RTEL1 genes. Idiopathic interstitial pneumonia (IIP) (n=12 [71%]), unexplained cytopenias (n=5 [29%]), and cirrhosis (n=2 [12%]) were most frequent clinical phenotypes at diagnosis. At median follow-up of 48 (range, 0-316) months, Kaplan-Meier estimate of overall survival, median (95% CI), was 182 (113, not reached) months. Treatment modalities included lung transplantation for IIP (n=5 [29%]), with 3 patients developing signs of acute cellular rejection (2, grade A2; 1, grade A1); danazol therapy for cytopenias (n=4 [24%]), with only 1 out of 4 patients showing a partial hematologic response; and allogeneic hematopoietic stem cell transplant for progressive bone marrow failure (n=2), with 1 patient dying from transplant-related complications. In summary, patients with STSs present with diverse clinical manifestations and require a multidisciplinary approach to management, with organ-specific transplantation capable of providing clinical benefit.