Disrupted Lymphocyte Homeostasis in Hepatitis-Associated Acquired Aplastic Anemia Is Associated with Very Low Telomere Lengths

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2408-2408
Author(s):  
Anne-Laure Grignon ◽  
Daria V. Babushok ◽  
Li Yimei ◽  
Helge Hartung ◽  
Ho-Sun Lam ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Aplastic Anemia ◽  
Telomere Length ◽  
Disease Severity ◽  
Bone Marrow Failure ◽  
Genetic Defect ◽  
Telomere Maintenance ◽  
Wilcoxon Test ◽  
Significant Difference ◽  
Lymphocyte Homeostasis

Abstract Acquired aplastic anemia (AA) is a hematologic disorder characterized by low blood counts and a hypocellular bone marrow, caused by autoimmune destruction of early hematopoietic cells. The diagnosis of AA is made by excluding other disorders that can present with bone marrow failure (BMF). Such disorders include dyskeratosis congenita (DC), a multisystem BMF syndrome, caused by an inherited defect in telomere maintenance. Although classical DC presents in childhood with stereotypical mucocutaneous changes, milder forms of telomere dysfunction associated with mutations in TERT and TERC genes can present with non-syndromic bone marrow failure clinically indistinguishable from AA. In clinical practice, lymphocyte telomere length measurements are used as a first-line screen for inherited telomeropathies before initiating treatment for AA. In our BMF center, we have observed that several patients with features of hepatitis-associated AA (HAA) had lymphocyte telomere lengths at diagnosis at or below the first percentile of age-matched controls, in the range similar to inherited telomere disorders. To confirm our initial observation, we performed a retrospective analysis of telomere lengths of consecutively enrolled HAA patients with non-hepatitis associated AA patients in our institution. A total of 30 patients with AA were included in this study: 10 had HAA and 20 had other AA (Table 1). The median age at telomere testing was 8.0 years (range 1-19 years). There was no significant difference in age or disease severity between the two groups (p=0.827). The patients' median lymphocyte telomere length (TL) was significantly lower in the HAA patients compared to AA (7.4kb versus 9.1kb, P= 0.021); the difference remained significant after adjusting for patient age (p<0.001). Strikingly, 5 of 10 HAA patients had telomeres at or below the 1st percentile of age-matched normal controls, within the diagnostic range for telomeropathies (Figure 1A). None of these 5 patients had clinical features of DC. As a comparison, TL measurements of genetically-confirmed DC patients (Figure 1) demonstrated TL below the 1st percentile for age-matched controls, and within a similar range to that seen in the HAA patients. To ensure that the significantly lower telomere lengths in the HAA patients were not caused by an occult TERT or TERC gene mutation, the five HAA patients with TL below the 1st percentile were screened for germline mutations in TERT and TERC. A known heterozygous polymorphism, Ala1062Thr was found in one patient, a known variant with no known telomere defect and no effect on telomere length. Because differences in lymphocyte activation and subset composition are known to impact telomerase activity, we hypothesized that alterations in lymphocyte populations caused by the unique inflammatory state of HAA could partly account for significantly shorter TL in this population. HAA patients exhibited significantly lower absolute lymphocyte counts and lower lymphocyte subsets across the board, as well as the decreased CD4/CD8 ratio compared to non-hepatitis AA patients (Figure 2). The median telomere length in the two groups was significantly correlated with lymphocyte counts (Pearson correlation coefficient 0.52, p=0.003). An altered lymphocyte homeostasis such as the one characteristic for HAA limits the specificity of telomere measurements as a screening method to identify patients with AA due to a genetic defect in telomere maintaining genes. As such, short telomeres in HAA in the absence of other features suggestive for DC does not necessarily warrant genetic testing for telomere length. Longitudinal studies of telomeres and study of clonal hematopoiesis in this population is ongoing. Table 1. Overall (n = 30) AA (n=20) HAA (n=10) P value* Patient Characteristic Gender, female n (%) 12 (40) 9 (45) 3 (30) 0.694 Gender, male n (%) 18 (60) 11 (55) 7 (70) Age at diagnosis, y, median (range) 8.0 (1-19) 8.3 (1-19) 7.5 (3-17) 0.827 Disease Severity, n (%) 0.999 Moderate 6 (20) 4 (20) 2 (20) Severe 22 (73) 15 (75) 7 (70) Very Severe 2 (7) 1 (5) 1 (10) Median Lymphocyte Telomere Length, kb (range) 8.9 (5.9-11.3) 9.1 (7.5-11.3) 7.4 (5.9-9.8) 0.021 ≤ 1st percentile of age-matched controls 5 0 5 1-10th percentile of age-matched controls 5 5 0 > 10th percentile of age-matched controls 20 15 5 *P-values are obtained by Fisher's exact test for gender and disease severity and by Wilcoxon test for age and telomere length. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures No relevant conflicts of interest to declare.

Significance of Telomere Length Measurement in the Diagnosis of Dyskeratosis Congenita.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 836-836
Author(s):  
Hong-Yan Du ◽  
Elena Pumbo ◽  
Akiko Shimamura ◽  
Adrianna Vlachos ◽  
Jeffrey M. Lipton ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Aplastic Anemia ◽  
Telomere Length ◽  
Bone Marrow Failure ◽  
Skin Pigmentation ◽  
Screening Method ◽  
Dyskeratosis Congenita ◽  
Telomere Maintenance ◽  
Healthy Controls ◽  
Mutation Carriers

Abstract Dyskeratosis congenita (DC) is a rare inherited bone marrow failure (BMF) syndrome. The classical features of DC include nail dystrophy, abnormal skin pigmentation, and mucosal leukoplakia. The diagnosis of DC can be difficult. Originally, the diagnosis was based on the presence of the classical mucocutaneous features. However, the identification of four genes responsible for DC (DKC1, TERC, TERT, and NOP10) showed that these mucocutaneous features are only present in a proportion of patients with DC. Additionally, screening for mutations in the affected genes is expensive and is negative in about 50% of patients with classical features of DC. The products of the genes mutated in DC are the components of the telomerase ribonucleoprotein complex, which is essential for telomere maintenance. Therefore it has been postulated that DC is a disease arising from excessive telomere shortening. Here we examined whether the measurement of telomeres could be used as a screening test to identify individuals with DC. For this purpose we examined telomere length in peripheral blood mononuclear cells from 169 patients who presented with bone marrow failure including 17 patients with DC, diagnosed by the presence of classical cutaneous features or the identification of mutations in DKC1, TERC or TERT, 28 patients with paroxysmal nocturnal hemoglobinuria, 25 patients with Diamond Blackfan anemia, 5 patients with Shwachman-Diamond syndrome, 8 patients with myelodysplastic syndrome, and 74 patients with aplastic anemia of unknown cause classified as idiopathic aplastic anemia. In addition we measured telomere length in 12 patients with idiopathic pulmonary fibrosis and in 45 individuals with a de novo deletion of chromosome 5p including the TERT gene. Their telomere lengths were compared with those of 202 age-matched healthy controls. Moreover, mutations were screened in the genes associated with DC. In cases where a mutation was identified, telomere length and mutations were also examined in all the family members. Our results show that all patients with DC and bone marrow failure have very short telomeres far below the first percentile of healthy controls. Not all mutation carriers, including some carriers of apparently dominant mutations, have very short telomeres. What is more, very short telomeres could be found in healthy individuals in these families, some of whom were not mutation carriers. These findings indicate that in patients with BMF the measurement of telomere length is a sensitive screening method for DC, whether very short telomeres in this setting are also specific for DC remains to be determined. However, in contrast to a previous study, we find that telomere length does not always identify mutation carriers in the families of DC.

Age-Adjusted Telomere Length Is Not Associated with Variation in Hematological Parameters in Ageing Women

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3102-3102
Author(s):  
Isabelle Fleury ◽  
Sylvie Provost ◽  
Claude Belisle ◽  
Lambert Busque
Keyword(s):  
Bone Marrow ◽  
Bone Marrow Transplantation ◽  
Telomere Length ◽  
Marrow Transplantation ◽  
Copy Number ◽  
Bone Marrow Failure ◽  
Telomere Maintenance ◽  
Hematological Parameter ◽  
Allogeneic Bone ◽  
Potential Biomarker

Abstract Background. Telomeres play a crucial role in maintaining physical integrity of chromosomes. In the absence of telomerase, telomere length (TL) shortens with each cell division up to a critical threshold where cellular senescence occurs. TL is inversely correlated with age, is longer in women than in men, and demonstrates a strong heritability. Normal blood counts are maintained through out life by an extraordinary number of cell divisions rendering telomere maintenance primordial to prevent stem cell exhaustion. In fact, some cases of bone marrow failure syndromes, such as aplastic anemia and dyskeratosis congenital, have been linked to mutation in the telomerase gene; and stressed hematopoiesis, such at it occurs during the first year following allogeneic bone marrow transplantation induces TL shortening. We hypothesized that individuals with shorter TL may have lower blood counts and a decreased bone marrow reserve. The evaluation of TL as a potential biomarker of ageing hematopoiesis is important in the context of bone marrow transplantation performed with increasingly old donors. Methods. We measured TL in 1583 women, predominantly aged over 60, all originating from 288 French-Canadian families using a real-time quantitative PCR method that measures the number of telomere repeats relatively to the copy number of a single copy number gene. Telomeres were adjusted for age. Pearson or Spearman correlations were used to determine association between age-adjusted TL (aTL) and hematological parameter according to, respectively, whether or not a normal distribution was observed for these data. A Bonferroni correction was further applied to set the statistical significance threshold. Results. aTL varied significantly between individuals of the cohort, but no correlation was detected with hemoglobin levels (−0,001; p=0,978), mean corpuscular volume (−0,031; p=0,403); leucocytes (0,055; p=0,139); neutrophils (0,078; p=0,036), monocytes, (0,059; p=0,113), eosinophils (−0,032; p=0,394) and platelets (0,030; p=0,428) counts. Conclusion. Based on our analysis, TL do not predict blood cells counts in ageing women and may not be a useful biomarker for donor selection. This could also suggest that there is a threshold beyond which TL has an effect on hematopoiesis and that point was not reached in our cohort.

Common Recurrent DKC1 Mutation A353V Does Not Support Telomere Maintenance in Induced Pluripotent Stem Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 50-50
Author(s):  
Baiwei Gu ◽  
Jason A. Mills ◽  
Jian-meng Fan ◽  
Deborah L. French ◽  
Monica Bessler ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Telomere Length ◽  
Pluripotent Stem Cells ◽  
Skin Fibroblast ◽  
Bone Marrow Failure ◽  
Ips Cells ◽  
Telomere Maintenance ◽  
Fibroblast Cells ◽  
Induced Pluripotent

Abstract Abstract 50 Dyskeratosis Congenita (DC) is a rare bone marrow failure syndrome showing considerable genetic and clinical heterogeneity. The most common form is the X-linked form due to mutations in the DKC1 gene encoding dyskerin, a protein important in telomere maintenance and ribosomal RNA biogenesis. Six other genes, all of whose products are involved in telomere maintenance, have been shown to be mutated in DC, together the seven genes accounting for about half of the known cases. The X-linked form can cause severe disease for which therapeutic options are limited. It is known that mutant dyskerin destabilizes telomerase RNA leading to rapidly shortening telomeres, accelerated stem cell aging and bone marrow failure. However the precise mechanism by which this occurs is not known. So far studies of the cell biology of DC stem and progenitor cells have been hampered by their scarcity in patients and their short life span and attempts to create mouse models have suffered from differences in telomere biology between mouse and human. An alternative approach that has recently become feasible is the production of induced pluripotent stem cells (iPSC) from patient fibroblasts that can then be used to investigate disease pathogenesis. Accordingly we generated iPSC from skin fibroblast from X-linked DC patients carrying DKC1 mutations Q31E, δ37A and 353V, and by using the classical OCT4, KLF4, SOX2 and cMYC 4-transcription factor system. Of particular interest is the A353V mutation since this is a recurrent mutation and accounts for about 40% of DKC1 mutations. In total, we obtained two Q31E clones, three δ37 clones and eight A353V clones. We found that all these DKC1 mutant iPS cells express decreased levels of dyskerin, in agreement with our mouse studies that show mutant proteins are relatively unstable. Mutant iPSC have very low levels of TERC (only 20–30% of the levels in WT iPSC) while TERT expression is the same as in WT cells. By using the TRAP assay, we found that both A353V and δ37 iPSC showed dramatically decreased telomerase activity; only 10–20 % compared to WT iPSC. After measuring the telomere length of both patient skin fibroblast cells and DKC1 mutant iPSC, we found A353V and δ37 iPSC lost the ability to elongate the telomere end during iPSC reprogramming while WT iPSC showed significantly increased telomere length compared to WT skin fibroblast cells. These results indicated that DKC1 iPSC are defective in telomere maintenance. In terms of ribosome biogenesis, we found that some snoRNA expression was slightly decreased including H/ACA snoRNAs E2, E3, U69, ACA10 and scaRNAs U90 and U93 while all C/D snoRNA we investigated were unchanged compared with WT iPS cells. We also found that DKC1 mutant iPS cells did not show significantly changes in ribosomal profiles or in the kinetics of rRNA processing. Together these results suggest that the iPSC faithfully reproduce the molecular features of the human disease and will prove to be a useful tool in investigations of the pathogenesis and treatment of DC. Disclosures: Bessler: Alexion Phamaceutical: Membership on an entity's Board of Directors or advisory committees; National Organization for Rare Dieases: Speakers Bureau.

Utility of Telomere in Diagnosis of Bone Marrow Failure Syndromes

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 4793-4793
Author(s):  
Hasan Ahmed Abdel-ghaffar ◽  
Hosam Zaghloul ◽  
Ahmed El-Waseef ◽  
Mohamed El-Naggar ◽  
Mohamed Mabed ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Telomere Length ◽  
Conflicts Of Interest ◽  
Bone Marrow Failure ◽  
Quantitative Polymerase Chain Reaction ◽  
Control Group ◽  
Hematopoietic Stem ◽  
Relative Telomere Length ◽  
Bone Marrow Failure Syndromes ◽  
Significant Difference

Abstract Background and aim of the work: Bone marrow failure syndromes (BMFS) includes inherited and acquired conditions. Inherited bone marrow failure includes a number of syndromes; with Fanconi anemia (FA) being the most common one of them. Telomeres are eroded with cell division, but in hematopoietic stem cell, maintenance of their length is mediated by telomerase. Short telomeres can result in instability of cell function where diseases occur. Bone Marrow Failure might be developed due to low telomerase activity or short telomeres. Our study is aiming to evaluate the utility of Real Time Quantitative-Polymerase Chain Reaction (RT-qPCR) in measuring the relative telomere length and its significance in diagnosis and prognosis of patients with BMFS. Materials and methods: The study includes 3 groups: A group of congenital BMF (29 patients), a group of acquired BMF (10 patients) and a third control group (15 cases). The relative telomere length is evaluated for them using RT-qPCR. Results: We have found that there is a significant difference in relative telomere length between congenital group and controls (p=0.001), also a significant difference between acquired group and controls (p= 0.029). However, there is no significant difference between congenital and acquired groups (p= 0.479). There is no significant correlation between the telomere length and the overall survival or prognosis of the patients of BMFS. Conclusion: We conclude that the telomere length is significantly altered in patients with BMFS whether being congenital or acquired compared to the control group. Disclosures No relevant conflicts of interest to declare.

scholarly journals Diagnostic utility of telomere length measurement in a hospital setting

2017 ◽  
Author(s):  
Jonathan K. Alder ◽  
Vidya Sagar Hanumanthu ◽  
Margaret A. Strong ◽  
Amy E. DeZern ◽  
Susan E. Stanley ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Telomere Length ◽  
Predictive Value ◽  
Bone Marrow Failure ◽  
Hospital Setting ◽  
Treatment Decisions ◽  
Telomere Maintenance ◽  
Short Telomere ◽  
Hematopoietic Stem

AbstractVery short telomere length (TL) provokes cellular senescence in vitro, but the clinical utility of TL measurement in a hospital-based setting has not been determined. We tested the diagnostic and prognostic value of TL measurement by flow cytometry and fluorescence in situ hybridization (flowFISH) in individuals with mutations in telomerase and telomere maintenance genes, and examined prospectively whether TL altered treatment decisions for patients with bone marrow failure. TL had a definable normal range across populations with discrete lower and upper boundaries. TL above the 50th age-adjusted percentile had a 100% negative predictive value for clinically relevant mutations in telomere maintenance genes, but the lower threshold for diagnosis was age-dependent. The extent of deviation from the age-adjusted median correlated with the age at diagnosis of a telomere syndrome as well as the predominant complication. Mild short telomere defects manifested in adults as pulmonary fibrosis-emphysema, while severely short TL manifested in children as bone marrow failure and immunodeficiency. Among 38 newly diagnosed patients with bone marrow failure, TL shorter than the 1st age-adjusted percentile enriched for patients with germline mutations in inherited bone marrow failure genes, such as RUNX1, in addition to telomere maintenance genes. The TL result modified the hematopoietic stem cell donor choice and/or treatment regimen in one-fourth of the cases (9 of 38,24%). TL testing by flowFISH has diagnostic and predictive value in definable clinical settings. In patients with bone marrow failure, it altered treatment decisions for a significant subset.

scholarly journals A multicenter trial of antithymocyte globulin in aplastic anemia and related diseases

Blood ◽  
1988 ◽  
Vol 72 (6) ◽  
pp. 1861-1869
Author(s):  
N Young ◽  
P Griffith ◽  
E Brittain ◽  
G Elfenbein ◽  
F Gardner ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Aplastic Anemia ◽  
Antithymocyte Globulin ◽  
Bone Marrow Failure ◽  
Multicenter Trial ◽  
Severe Aplastic Anemia ◽  
Transfusion Independence ◽  
Group I ◽  
Significant Difference ◽  
To Receive

One hundred fifty patients with bone marrow failure were treated in three groups with antithymocyte globulin (ATG; Upjohn, Kalamazoo, MI) in a multicenter trial. Patients were assessed at 3, 6, and 12 months after initiation of treatment by three criteria: transfusion independence, clinical improvement, and blood counts. Group I consisted of 77 patients with acute severe aplastic anemia, randomized to receive either ten or 28 days of ATG. There was no significant difference between the two arms of this protocol: 47% of all patients were clinically improved and 31% were transfusion independent at 3 months. Of the severely affected patients, 27% died before 3 months; most deaths occurred early in treatment. Factors associated with survival in severely affected patients included male sex, age less than 40 years, absolute neutrophil count greater than 200/microL, and idiopathic etiology. Neutrophil counts generally increased by 8 weeks after treatment, but patients continued to show improvement to 1 year posttreatment. In Group II, 44 patients with moderate or chronic severe aplastic anemia were randomized to receive either ten days of ATG or 3 months of high-dose nandrolone decanoate. No patient initially treated with androgens recovered, but 28% of ATG-treated cases achieved transfusion independence at 3 months. Group III consisted of patients with a variety of bone marrow failure syndromes. Patients with pancytopenia and cellular bone marrow showed response rates similar to those of patients with chronic or moderate aplastic anemia.

Telomerase Gene Mutation Screening and Telomere Length Detection in Chinese Patients with Bone Marrow Failure Syndrome.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1047-1047
Author(s):  
Bing Han ◽  
Bo Liu ◽  
Yongqiang Zhao
Keyword(s):  
Bone Marrow ◽  
Aplastic Anemia ◽  
Small Group ◽  
Telomere Length ◽  
Gene Mutation ◽  
Bone Marrow Failure ◽  
Chinese Patients ◽  
Chinese People ◽  
Bone Marrow Failure Syndrome ◽  
Tert Mutation

Abstract Background Acquired bone marrow failure syndrome (BMF) is a group of diseases include aplastic anemia(AA), melodysplastic syndrome (MDS) and paraoxymal nocturnal hemoglobinuria (PNH). Some BMF patients have short telomeres in their peripheral nucleated cells. The length of telomere is maintained by a group of enzymes called telomerase complex. The core components of this complex are a RNA template and a reverse transcriptase, called TERC and TERT, respectively. Recently several studies in the west and Japan have disclosed the presence of telomerase complex gene mutation in a small group of patients with acquired bone marrow failure. They speculated that this small group of patients might represent a subset of cryptogenic Dyskeratosis Congenita (DKC), in which the premature exhaustion of hematopoietic reservoir is caused by mutations in the telomerase gene. This group of patients, though very small in number, would benefit from early bone marrow transplantation instead of traditional immunosuppressive therapy. The incidence of aplastic anemia in Chinese people is relatively high compared with that in the western country. But there has so far been no study in China about the incidence of telomerase gene mutation in acquired bone marrow failure and its relationship with telomere length. Objectives To study the incidence of telomerase gene (namely TERC and TERT ) mutation in Chinese patients with acquired bone marrow failure and explore its relationship with telomere shortening. Methods Blood samples from 90 patients with AA, MDS, and PNH in northern China were collected and performed TERC and TERT mutation analysis. Telomere length was measured by Southern blotting and compared with their normal counterparts. Results 2 TERC mutations (n37 A→G, reported previously ; n66G→C) and 2 TERT mutations (n1870G→T (E/*); n1780G→T (S/I) ) were identified in 90 BMF patients. Among them, 3 mutations are reported first time. 1 patient with TERT mutation, however, was finally diagnosed as DKC instead of acquired AA, making the incidence of telomerase gene mutation in Chinese people with acquired bone marrow failure 3.4%, similar to that of the western people. Southern Blot analysis showed the small group of patients carrying TERC and TERT mutations has very short telomeres, compared with normal controls and with their aplastic counterparts. Conclusions The incidence of telomerase gene mutation in Chinese people with acquired bone marrow failure is 3.4%, similar to that of the western people. This small group of patients has very short telomeres, it is thus clinically important to screen for this small group of patients.

scholarly journals Very short telomere length by flow fluorescence in situ hybridization identifies patients with dyskeratosis congenita

Blood ◽  
2007 ◽  
Vol 110 (5) ◽  
pp. 1439-1447 ◽  
Author(s):  
Blanche P. Alter ◽  
Gabriela M. Baerlocher ◽  
Sharon A. Savage ◽  
Stephen J. Chanock ◽  
Babette B. Weksler ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
In Situ Hybridization ◽  
Fluorescence In Situ Hybridization ◽  
Telomere Length ◽  
Bone Marrow Failure ◽  
Correct Diagnosis ◽  
Dyskeratosis Congenita ◽  
Telomere Maintenance

Abstract Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome in which the known susceptibility genes (DKC1, TERC, and TERT) belong to the telomere maintenance pathway; patients with DC have very short telomeres. We used multicolor flow fluorescence in situ hybridization analysis of median telomere length in total blood leukocytes, granulocytes, lymphocytes, and several lymphocyte subsets to confirm the diagnosis of DC, distinguish patients with DC from unaffected family members, identify clinically silent DC carriers, and discriminate between patients with DC and those with other bone marrow failure disorders. We defined “very short” telomeres as below the first percentile measured among 400 healthy control subjects over the entire age range. Diagnostic sensitivity and specificity of very short telomeres for DC were more than 90% for total lymphocytes, CD45RA+/CD20− naive T cells, and CD20+ B cells. Granulocyte and total leukocyte assays were not specific; CD45RA− memory T cells and CD57+ NK/NKT were not sensitive. We observed very short telomeres in a clinically normal family member who subsequently developed DC. We propose adding leukocyte subset flow fluorescence in situ hybridization telomere length measurement to the evaluation of patients and families suspected to have DC, because the correct diagnosis will substantially affect patient management.

Telomere Dysfunction in Bone Marrow Failure.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. SCI-12-SCI-12
Author(s):  
Peter M. Lansdorp
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Aplastic Anemia ◽  
Telomere Length ◽  
Bone Marrow Failure ◽  
Tumor Development ◽  
Dyskeratosis Congenita ◽  
Cell Numbers ◽  
Tert Gene

Abstract Abstract SCI-12 In order to distinguish a normal telomere from a double strand break, a minimum number of telomere repeats must “cap” each chromosome end. The length of each repeat array will reflect a unique history of addition and losses. Telomere losses are known to occur sporadic as well as with every replication cycle. Losses of telomeric DNA are countered by the telomerase enzyme containing telomerase RNA (encoded by the TERC gene) and a reverse transcriptase protein (encoded by TERT gene) as minimal components. Telomerase levels are high in cells of the germline and immortal cellines and the telomere length is typically maintained in such cells. In contrast, telomerase activity is limiting in most human somatic (stem) cells and as a result the average length of telomere repeats in most somatic cells shows a highly significant decline with age. The hypothesis that loss of telomere repeats acts as a “mitotic clock” and a tumor suppressor mechanism in stem cells is strongly supported by recent studies of patients with mild telomerase deficiency resulting from haplo-insufficiency for either the TERC or TERT gene. Such genetic defects can give rise to various disorders including autosomal dominant Dyskeratosis Congenita (DKC), aplastic anemia, liver fibrosis and pulmonary fibrosis. Other recent studies have revealed that amplification of the hTERT gene is one of the most common genetic abnormalities in various cancers. Paradoxically, it is becoming clear that SNPs within the TERT locus are among the most reproducible risk factors for the development of different types of cancer including lung cancer, acute myeloid leukemia and chronic lymphocytic leukemia. The links between hypo- and hyperproliferative consequences of inborn telomerase deficiencies and SNP's in the TERT gene are poorly understood. It seems plausible that the increased risk of leukemia development in aplastic anemia, myelodysplastic syndrome and Dyskeratosis Congenita, results from stem cell failure. Could reduced stem cell numbers by itself provide a risk factor for tumor development? More direct measures of stem cell numbers in vivo are needed to examine this possibility and the relationship between stem cell numbers and tumor development in patients with defective telomere maintenance as well as in normal individuals as a function of age. Measurements of the average telomere length as well as the length of telomere repeats at individual chromosome ends in specific cells and tissues will further calrify the involvement of telomeres in bone marrow failure, normal aging and tumor biology. Disclosures Lansdorp: Repeat Diagnostics Inc.: Equity Ownership.

scholarly journals Telomerase Gene Complex Mutations Are Common in Myelodysplastic Syndromes Patients

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 1899-1899
Author(s):  
Mariam Ibañez ◽  
Jie Jiang ◽  
Shreyans Gandhi ◽  
Mian Syed ◽  
Alexander E Smith ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Telomere Length ◽  
Chromatin Remodeling ◽  
Myelodysplastic Syndromes ◽  
Prognostic Significance ◽  
Telomere Maintenance ◽  
Targeted Sequencing ◽  
Gene Complex ◽  
Wild Type ◽  
Significant Difference

Abstract Telomerase complex maintains telomeres and protects genomic DNA from degradation during cell divisions. Abnormal telomerase function can result in chromosomal instability predisposing to malignant transformation. Short telomere is a typical feature of inherited bone marrow failures syndromes (BMFs), especially dyskeratosis congenital (DC), caused by mutations in genes encoding components of the telomerase gene complex (TGC), shelterin proteins and DNA helicases. Telomere attrition have been associated with leukemic transformation in myelodysplastic syndromes (MDS), as well as complex cytogenetic aberrations, and also with the development of secondary MDS and acute leukemia (AML) after chemotherapy. However, the incidence of TGC mutations in de novo MDS remains largely unknown. Recurrent somatic mutations in genes involving epigenetic, spliceosome, cell signaling and proliferation pathways are common in MDS and have prognostic significance. Identifying specific associations between mutational patterns helps characterize disease biology and thereby improve the therapeutic strategies To determine the incidence of TGC mutations and study theassociation of TGC mutation patterns with recurrently mutated genes in MDS. To correlate TGC mutations with telomere length, clinical phenotypes and outcome of patients. We undertook a massively parallel targeted sequencing of all 10 TGC, (TERT, TERC, TINF2, NHP2, NOP10, RTEL1, CTC1, DKC1, USB1 and WRAP53) in a cohort of 174 MDS patients. Furthermore, we measured the telomere length (T/S ratio) by a multiple quantitative real-time PCR in bone marrow mononuclear cells. Additionally, in 151/174 MDS patients, we studied 22 recurrently mutated MDS-associated genes (MGP) by targeted sequencing. Among the whole cohort, 61% were male. The median age of patients was 63 years (range 17–87). WHO subtypes were 45 RA/RARS/isolated de5q (26%); 50 RCMD/RCMD-RS, (29%); 41 RAEB 1/2, (24%); 8 AML secondary to MDS, (5%); 8 (5%) MDS/MPD and 3 CMML (2%). IPSS cytogenetic risk groups were: 108 patients with good risk (62%), 21 intermediate (12%) and 32 poor risk, (18%) and cytogenetics failed in 10 patients (6%). IPSS categories were low risk 41(24%), intermediate-1: 54 (31%), intermediate-2: 30 (17%), high risk: 13 (7%) and 10 (6%) patients were not evaluated (proliferative CMML and MPD/MDS). Transfusion dependency was present in 80 patients (46%). Twenty nine TGC mutations were present in 26 patients (15%)(figure 1). Twenty-three patients (88%) had TERT mutations, 3 RTEL1 mutations (13%) and 1 TINF2 mutations (4%) with variant allelic frequency around 50%. Two patients presented more than one mutation in TGC genes. Most of mutations in TGC genes were previously described as germ line variants inpatients with DC and inherited aplastic anemia. All mutations found in TERT gene were missense. In patients with TGC mutations, the median T/S ratio was 1.1 (range 0.4–3.5), shorter than the T/S ratio of age-matched controls, although no statistically significant difference was seen in T/S ratio when compared to wild type. (P=0.527). TGC variations did not correlate with clinical features such as age, cytogenetic risk or IPSS, and had no impact on the overall survival (P=0.659). In 151 MDS patients, 73% (n=110) had at least one known somatic mutation in the MGP (21% TET2, 15% ASXL1, 14% TP53, 11% DNMT3A, 11% U2AF1, 9% IDH2, 9% SRSF2, 6% EZH2, 4% NRAS, 4% CEBPA, 3% SF3B1, 3% RUNX1, 2% JAK2, 2% FLT3, 1% cCBL). Among the MGP mutated patients, 13% carried also TGC mutations concurrently (Table 1). Chromatin remodeling gene mutationswere less frequent in patients with TGC mutations (P=0,001) as compared to patient with wild type TGC. We show TGC mutations are frequent in MDS patients (15%). The presence of known TERT variants seen in our cohort demonstrates a clear pathogenic association between MDS phenotype and telomerase mutations, rather than these being bystander variants. Although the heterozygous nature of these abnormalities indicates an inherited variant, the absence of telomere shortening argues against this concept and needs further evaluation. Chromatin remodeling gene mutations are less frequent in patients with TGC mutations. These findings suggest that defective telomere maintenance through TGC mutations might play an important etiological role in the multistep process in pathogenesis of a subset of MDS. Figure 1 Figure 1. Disclosures Mufti: Onconova Therapeutics, Inc: Research Funding.

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