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.

Antioxidant Treatment Rescues An Accelerated Aging Phenotype In Dyskerin Mutated Bone Marrow Stem Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2614-2614
Author(s):  
Baiwei Gu ◽  
Jian-meng Fan ◽  
Monica Bessler ◽  
Philip J Mason
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Cell Function ◽  
Bone Marrow Failure ◽  
Dyskeratosis Congenita ◽  
Untreated Group ◽  
Telomere Maintenance ◽  
Antioxidant Treatment ◽  
Transplantation Experiments

Abstract Abstract 2614 X-linked Dyskeratosis Congenita (DC) is due to mutations in the DKC1 gene, which encodes the protein dyskerin. Dyskerin is a highly conserved nucleolar protein that, as part of a specialized nucleolar RNP, catalyzes the pseudouridylation of specific residues in newly synthesized ribosomal RNAs and spliceosomal snRNAs. Dyskerin also associates with telomerase and is involved in telomere maintenance. In addition to the well known effect of telomere homeostasis on cancer, it is evident that telomere maintenance may also be important in replicative aging because of telomere shortening due to the limited expression of telomerase activity in dividing somatic cells. Accumulating evidence suggests that dysfunctional telomeres resulting in premature cellular senescence is the primary cause of bone marrow failure in dyskeratosis congenita. It is important to determine the mechanism whereby Dkc1 mutations lead to premature cellular senescence in bone marrow. We have produced a line of mice containing a mutation, Dkc1Δ15, which is a copy of a pathogenic human mutation. Male Dkc1Δ15 mice showed a decrease in the proportion of B and T lymphocytes in peripheral blood and reduced body weight with age but no overt bone marrow failure syndrome phenotypes. Our previous competitive bone marrow transplantation experiments showed that the Dkc1Δ15 mutation caused decay of stem cell function with age. Bone marrow from older Dkc1Δ15 mice was markedly inefficient in repopulation studies compared with bone marrow from age matched wild type mice. We also found that N-acetyl cysteine (NAC) could at least partially rescue the growth disadvantage of dyskerin mutant spleen cells or fibroblasts which was associated with accumulation of DNA damage and reactive oxygen species. To determine if NAC, or other antioxidants might be useful therapeutically it is important to determine their effects on stem cell function, which is defective in DC. To this end we established a cohort of mice that were given NAC in their drinking water (1mg/ml) from 3-weeks of age and maintained on NAC for 1 year. We found that long term NAC treatment did not show significant side effects on the mice. They had slightly increased neutrophils, but no difference in life span and body weight compared with the untreated group. Impressively, old male Dkc1Δ15 mice showed corrected B and T cell proportions in peripheral blood after treatment with NAC. Competitive bone marrow transplantation experiments were carried out in which a 1:1 mixture of BM cells from mutant and WT mice was used to repopulated lethally irradiated recipient mice. These experiments showed that, when taken from NAC treated animals, old Dkc1Δ15 BM cells could compete with age matched WT cells with 40–45% of Dkc1Δ15 cells in primary recipients compared with only 20% for the untreated group. Moreover, after secondary transplantation, cells from the NAC treated group still represent 15–20% of Dkc1Δ15 cells in recipients while those from the untreated group could not be detected. These results strongly suggest that NAC treatment can partially restore the bone marrow repopulating ability of Dkc1Δ15 stem cells. Together with our previous results these data suggest that a pathogenic Dkc1 mutation, through its effect on telomerase, initiates stem cell aging before telomeres are short and that increased oxidative stress might play a role in this process. Moreover the effects of the mutation may be prevented or delayed by antioxidant treatment, although the precise mechanism will be the subject of future investigation. Disclosures: Bessler: Alexion Pharmaceutical Inc: Consultancy; Novartis: Membership on an entity's Board of Directors or advisory committees; Taligen: Consultancy.

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.

scholarly journals Genetic Dissection of Dyskeratosis Congenita-Causing Mutations in TINF2 Using Human Pluripotent and Hematopoietic Stem Cell Models

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 2178-2178
Author(s):  
Seunga Choo ◽  
Franziska K. Lorbeer ◽  
Samuel G. Regalado ◽  
Sarah B. Short ◽  
Shannon Wu ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Telomere Length ◽  
Hematopoietic Stem Cell ◽  
Research Funding ◽  
Dyskeratosis Congenita ◽  
Model Systems ◽  
Telomere Shortening ◽  
Hematopoietic Stem

Abstract The length of telomeres, which cap the ends of linear chromosomes and provide genomic stability, is tightly regulated in adult stem cells. The telomere reserve in the stem cell population sets the replicative potential of its differentiated progeny. For this reason, abnormally short telomeres in stem cells restrict the number of cell divisions that their differentiated progenies can undergo, eventually resulting in stem cell depletion and tissue failure syndromes. Telomere biology disorders (TBDs) display a broad range of clinical features, age of onset, and severity, which are all correlated with the extent of abnormal telomere shortening. One such early-onset TBD is dyskeratosis congenita (DC), which is a bone marrow predisposition syndrome characterized by a mucocutaneous triad (oral leukoplakia, nail dystrophy, and abnormal skin pigmentation) as well as other conditions driven by premature tissue aging. The leading cause of death in DC patients is bone marrow failure and hematopoietic stem cell transplantation is the only definite intervention to restore hematopoiesis. TINF2, which encodes the TIN2 protein, is mutated in 12% of patients and thereby the second most frequently altered gene in DC cases. TIN2 is a member of the shelterin protein complex bridging the double-strand binding shelterin proteins TRF1/TRF2, and the TPP1/POT1 heterodimer. Such interactions implicate a complex role of TIN2 in telomere length regulation: First, TIN2 stabilizes TRF1, which is a negative regulator of telomere length. Secondly, TPP1, which recruits telomerase, strictly requires TIN2 for telomere elongation and maintenance. TINF2-DC mutations are uniformly heterozygous and localize to a 30 amino acid coding stretch in exon 6 called the 'DC cluster'. TINF2-DC mutations usually arise de novo and result in an earlier disease onset, shorter telomeres, and a more severe manifestation compared to other heterozygous DC-causing mutations in genes such as TR and TERT, which encode the components of the telomerase enzyme. How TINF2-DC mutations cause telomere shortening is unknown. Specifically, whether telomere shortening is caused by reduced telomerase action at telomeres or by degradation of telomeric DNA remains unresolved as studies using different model systems report contrasting results. The discrepancy could be attributed to differences in the model systems used in the studies, highlighting the need for a genetically trackable, primary preclinical human model system. Here, we report the development of two novel endogenous, isogenic model systems to study TINF2-DC mutations. First, we generated human embryonic stem cells (hESCs) engineered to express the TINF2-DC T284R mutation from the endogenous locus, which recapitulated the short telomere phenotype observed in DC patients. Using this model, we identified a gene editing strategy that elongates telomeres in the mutant stem cells and eventually restores replicative potential of the differentiated cells. Next, we used a xenotransplantation model of donor-derived human hematopoietic stem cells (hHSCs) to test the effects of target gene modifications on telomere length and proliferative capacity in vivo. We demonstrate that our models robustly complement each other and offer direct insights into the disease mechanism as well as avenues to potential therapeutic approaches. Figure 1 Figure 1. Disclosures Bertuch: Elixirgen Therapeutics: Consultancy; ImmunityBio: Current equity holder in publicly-traded company; NIH/NCI,: Research Funding; DOD: Research Funding; Hyundai Hope on Wheels: Research Funding.

Treatment of Severe Aplastic Anemia with Porcine Anti-Human Lymphocyte Globulin

2020 ◽  
Vol 26 (22) ◽  
pp. 2661-2667
Author(s):  
Qi Lv ◽  
Zhang Huiqin ◽  
Xiao Na ◽  
Liu Chunyan ◽  
Shao Zonghong ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Aplastic Anemia ◽  
Bone Marrow Failure ◽  
New Product ◽  
Therapeutic Effects ◽  
First Line ◽  
Bone Marrow Failure Syndrome ◽  
Hematopoietic Stem

Aplastic anemia (AA) is a bone marrow failure syndrome characterized by pancytopenia. Decreased numbers of hematopoietic stem cells and impaired bone marrow microenvironment caused by abnormal immune function describe the major pathogenesis of AA. Hematopoietic stem cell transplantation and immunesuppressive therapy are the first-line treatments for AA. Porcine anti-lymphocyte globulin (p-ALG) is a new product developed in China. Several studies have shown that p-ALG exhibited good therapeutic effects in AA.

scholarly journals Generation of Dyskeratosis Congenita-like Hematopoietic Stem Cells through the Stable Inhibition of DKC1

2020 ◽  
Author(s):  
Carlos Carrascoso-Rubio ◽  
Hidde A. Zittersteijn ◽  
Laura Pintado-Berninches ◽  
Beatriz Fernández-Varas ◽  
M. Luz Lozano ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Hematopoietic Stem Cell Transplantation ◽  
Stem Cell Transplantation ◽  
Hematopoietic Stem Cells ◽  
Bone Marrow Failure ◽  
Dyskeratosis Congenita ◽  
Hematopoietic Stem ◽  
Human Cd34

Abstract Dyskeratosis congenita is a rare telomere biology disorder, which results in different clinical manifestations, including severe bone marrow failure. To date, the only curative treatment for bone marrow failure in dyskeratosis congenita patients is allogeneic hematopoietic stem cell transplantation. However due to the toxicity associated to allogeneic hematopoietic stem cell transplantation in dyskeratosis congenita, new non-toxic therapies are recommended to improve the life expectancy of these patients. Since bone marrow biopsies are not routinely performed during the follow-up of dyskeratosis congenita patients, the availability of dyskeratosis congenita hematopoietic stem cells constitutes a major limitation in the development of new hematopoietic therapies for dyskeratosis congenita. Here we aimed at generating dyskeratosis congenita-like human hematopoietic stem cells in which the efficacy of new therapies could be investigated. X-linked dyskeratosis congenita is one of the most frequent variants of dyskeratosis congenita and is associated with an impaired expression of the DKC1 gene. In this study we thus generated dyskeratosis congenita-like hematopoietic stem cells based on the stable knock-down of DKC1 in human CD34+ cells, using lentiviral vectors encoding for DKC1 short hairpin RNAs. At a molecular level, DKC1-interfered CD34+ cells showed a decreased expression of TERC, as well as a diminished telomerase activity and increased DNA damage. Moreover, DKC1-interfered human CD34+ cells showed defective clonogenic ability and were incapable of repopulating the hematopoiesis of immunodeficient NSG mice. The development of dyskeratosis congenita-like hematopoietic stem cells will facilitate the understanding of the molecular and cellular basis of the bone marrow failure characteristic of dyskeratosis congenita patients, and will serve as a platform for the development of new hematopoietic therapies for dyskeratosis congenita patients.

scholarly journals Revesz syndrome revisited

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Michael Karremann ◽  
Eva Neumaier-Probst ◽  
Frank Schlichtenbrede ◽  
Fabian Beier ◽  
Tim H. Brümmendorf ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Stem Cell Transplantation ◽  
Cell Transplantation ◽  
English Literature ◽  
Bone Marrow Failure ◽  
Dyskeratosis Congenita ◽  
Kaplan Meier ◽  
Low Prevalence

Abstract Background Revesz syndrome (RS) is an extremely rare variant of dyskeratosis congenita (DKC) with only anecdotal reports in the literature. Methods To further characterize the typical features and natural course of the disease, we screened the English literature and summarized the clinical and epidemiological features of previously published RS cases. In addition, we herein describe the first recorded patient in central Europe. Results The literature review included 18 children. Clinical features are summarized, indicating a low prevalence of the classical DKC triad. All patients experienced early bone marrow failure, in most cases within the second year of life (median age 1.5 years; 95% CI 1.4–1.6). Retinopathy occurred typically between 6 and 18 months of age (median age 1.1 years; 95% CI 0.7–1.5). The incidence of seizures was low and was present in an estimated 20% of patients. The onset of seizures was exclusively during early childhood. The Kaplan–Meier estimate of survival was dismal (median survival 6.5 years; 95% CI 3.6–9.4), and none of the patients survived beyond the age of 12 years. Stem cell transplantation (SCT) was performed in eight children, and after a median of 22 months from SCT four of these patients were alive at the last follow up visit. Conclusion RS is a severe variant of DKC with early bone marrow failure and retinopathy in all patients. Survival is dismal, but stem cell transplantation may be performed successfully and might improve prognosis in the future.

A Novel hTERC Deletion Manifesting with Features of Dyskeratosis Congenita and Genetic Anticipation.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4157-4157
Author(s):  
Stan Benke ◽  
D. S. Houston ◽  
Inderjeet Dokal ◽  
Tom Vulliamy
Keyword(s):  
Bone Marrow ◽  
Telomere Length ◽  
Peripheral Blood ◽  
Autosomal Dominant ◽  
Bone Marrow Failure ◽  
Macrocytic Anemia ◽  
Phenotypic Expression ◽  
Dyskeratosis Congenita ◽  
Sequencing Analysis ◽  
Genetic Anticipation

Abstract The gene encoding the RNA component of human telomerase (hTERC) is mutated in families with the autosomal dominant form of dyskeratosis congenita (DC). The phenomenon of genetic anticipation has recently been reported to accompany this form of DC, with disease severity increasing in offspring of affected individuals. It has been postulated that anticipation in these families relates to the adverse impact of hTERC mutations on inherited telomere length, with progressive telomere shortening seen in succeeding generations (Nat Gen2004; 36:447). We describe here a novel hTERC mutation, with affected individuals presenting in adulthood with mild mucocutaneous abnormalities, bone marrow failure and a pattern of penetrance supporting the presence of disease anticipation. The proband in the family studied presented at age 49 with squamous cell carcinoma of the tongue and a history of oral leukoplakia which he had developed at age 30. Peripheral blood on presentation was remarkable only for a mild macrocytic anemia. During treatment of his malignancy, severe and irreversible bone marrow hypoplasia was precipitated by a single cycle of cisplatinum chemotherapy. The patient’s brother at age 25 had been previously diagnosed with severe aplastic anemia; this was refractory to standard immunosuppression with cyclosporine and antithymocyte globulin. No somatic abnormailites were identified in this patient. Testing for Fanconi anemia in both siblings was negative. Direct sequencing analysis of hTERC in these patients revealed both to be heterozygous for a novel hTERC mutation (79 deletion C). Further studies among family members documented heterozygosity for the mutation in the mother of these two siblings. At age 77, she displayed none of the mucocutaneous signs associated with DC, while the only abnormality seen in her peripheral blood was an elevated mean corpuscular volume. The hTERC mutation seen in this family most likely exerts its effects through disruption of the pseudoknot domain. The findings of an individual with normal longevity, minimal phenotypic expression and affected offspring are further evidence of genetic anticipation being an important feature of autosomal dominant DC. Correlation with determination of telomere length has been initiated.

of the Telomerase RNA (TERC) and Telomerase Reverse Transcriptase (TERT) in Japanese Children with Aplastic Anemia.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3750-3750
Author(s):  
Juan Liang ◽  
Hirosi Yagasaki ◽  
Koji Kato ◽  
Kazuko Kudo ◽  
Seiji Kojima
Keyword(s):  
Bone Marrow ◽  
Aplastic Anemia ◽  
Bone Marrow Failure ◽  
Unrelated Donor ◽  
Allogeneic Bone ◽  
Healthy Controls ◽  
Japanese Children ◽  
Ribonucleoprotein Complex ◽  
Base Substitutions ◽  
Tert Gene

Abstract It is well known that the incidence of aplastic anemia (AA) is much higher in Japan than in Western countries. However the reason for this finding is not known. Genetic backgrounds related to AA may be different between populations. Recent studies have shown that some patients with apparently “acquired” AA have mutations in telomerase ribonucleoprotein complex genes such as TERC and TERT. We studied 96 Japanese children with acquired AA (age range, 0–16 years; median, 7 years) and 59 healthy controls for mutations in TERC and TERT genes. Of these children, 35 were classified as having nonsevere AA, 39 as having severe AA, and 22 as having very severe AA. In 7 patients, AA was secondary to acute hepatitis. We extracted DNA samples from peripheral blood and all exons and flanking introns of TERT and TERC were amplified by PCR using 19 primer pairs (1 TERC, 18 TERT). To determine the sequence, the PCR products were analyzed by ABI/PRISM 3100 automated sequencer. Telomere lengths of leukocytes were assessed by flow-FISH. For the TERC gene, no mutation was found. One polymorphism (n514 G>A) was observed in 57/96 (59.4%) of patients. The same substitutions were detected in 31/59 (52.5%) healthy controls. For the TERT gene, two novel heterozygous, nonsynonymous mutations were identified (exon5; n2045 G>A, exon6; n2177 C>T). These base substitutions introduce an amino acid change-G682D and T726M, respectively. Neither patient had any clinical characteristics suggesting constitutional bone marrow failure syndrome. The n2177C>T substitution was identified in a 9-year-old girl with very severe AA who failed to respond to immunosuppressive therapy. She received an allogeneic bone marrow transplant (BMT) from an unrelated donor, but did not engraft. She was then treated by a second BMT from an HLA haploidentical her mother. Her blood cells had a very short telomere compared with that of age-matched controls. Another patient carrying the n2045G>A substitution had nonsevere AA and did not require any specific medication for 8 years. Six polymorphisms in exons of the TERT gene were identified in 102 unrelated patients (n915 G>A, n2097 C>T, n2520 G>A, n2946 T>C, n3039 C>T, and n3366 G>A). The allele frequencies of these silent base substitutions were 38/192 (19.8%), 3/192 (1.6%), 1/192 (0.5%), 1/192 (0.5%), 57/192 (29.7%), 2/192 (1.0%), respectively. Additionally, we identified 5 polymorphisms in introns of the TERT genes in 64 patients (IVS4+143 A>G, IVS9+11 C>T, IVS13+45 C>T, IVS15+136 G>A, and IVS16+81 C>T). The frequencies were 52/192 (27.1%), 3/192 (1.6%), 7/192 (3.6%), 1/192 (0.5%), and 1/192 (0.5%), respectively. Except for two substitutions (n915G>A and IVS4+143A>G), the other 9 were not listed in the SNP database. We found a few patients with AA carrying mutations of telomerase ribonucleoprotein complex genes. Because the incidence of these mutations is not higher than that in Western populations, this genetic difference does not explain the higher incidence of AA in Japanese children.

Erythrocytosis after Allogeneic Bone Marrow Transplantation in the Patients with Severe Aplastic Anemia.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 5327-5327
Author(s):  
Soo-Jeong Park ◽  
Chi-Wha Han
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Aplastic Anemia ◽  
Bone Marrow Failure ◽  
Allogeneic Bone Marrow Transplantation ◽  
Severe Aplastic Anemia ◽  
Allogeneic Bone ◽  
Laboratory Findings ◽  
Normal Ranges ◽  
Serum Erythropoietin Level

Abstract Severe aplastic anemia (sAA) is a bone marrow failure disorder which is mostly a consequence of immunologically mediated stem cell destruction. Stem cell transplantation (SCT) from a histocompatible sibling is a treatment of choice for this disease but major obstacles in success of allogeneic SCT include graft-versus-host disease (GVHD), graft rejection and treatment related toxicities. We describe two cases of post-transplant erythrocytosis in severe aplastic anemia. About 5 years later, following HLA-matched sibling transplantation, the patients (45-year-old male and 43-year-old male) developed a sustained increase in hemoglobin (>17 g/dL) and hematocrit (> 50%), an increase in the frequency of headache, and new onset of dizziness and malaise. Laboratory findings demonstrated normal ranges of other blood components and serum erythropoietin level, and they did not have smoking or other drugs. Also, they did not have a hepatosplenomegaly or other organ diseases. We initiated a therapeutic phlebotomy program (400 ml q 2–4 weeks and then q 2–3 months for 5 years) in order to lower the hematocrit to available values (Hb < 14.5 g/dL), and to induce iron deficiency (Fig 1). Repeated phlebotomy resulted in a decrease in symptoms and a total volume of blood venesection is about 9,200 – 11,200 ml so far. Figure 1. Hemoglobin change after bone marrow transplantations. Figure 1. Hemoglobin change after bone marrow transplantations.

Homozygous and Compound Heterozygous Mutations in the Telomerase Reverse Transcriptase Gene in Two Families with Spontaneous Dyskeratosis Congenita and Idiopathic Aplastic Anemia.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1675-1675
Author(s):  
Hong-Yan Du ◽  
Elena Pumbo ◽  
Peter Manley ◽  
David B. Wilson ◽  
Philip Mason ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Autosomal Recessive ◽  
Amino Acid Change ◽  
Autosomal Dominant ◽  
Bone Marrow Failure ◽  
Gene Mutations ◽  
Dyskeratosis Congenita ◽  
Compound Heterozygous ◽  
The Family ◽  
Tert Gene

Abstract Dyskeratosis congenita (DC) is a rare inherited bone marrow failure syndrome. Classically, DC presents with progressive bone marrow failure, abnormal skin pigmentation, nail dystrophy, and mucosal leukoplakia. The pattern of inheritance in families with DC suggests an X-linked recessive, an autosomal dominant, and an autosomal recessive form of DC. However, in the majority of patients the occurrence of the disease is sporadic or the family history is unknown. Mutations in four different genes have been associated with DC so far. Mutations in DKC1 have been shown to account for the X-linked form of DC and DKC1 de novo mutations account for about one third of male patients with sporadic disease. Mutations in the telomerase RNA TERC and in the catalytic subunit of telomerase, TERT, have been shown to be responsible for the autosomal dominant form of DC. Interestingly, patients with heterozygous mutations in TERC and TERT often show a milder form of disease and a later age of onset and often lack the classic mucocutaeous features, thus are classified as atypical DC. Very recently homozygosity for a mutation in NOP10 has been identified in one family with autosomal recessive disease. The products of the genes mutated in DC are all components of the telomerase complex, suggesting that disease in patients with DC is caused by a defect in telomere maintenance. Here we investigated two patients, one UPN # 199.001 presenting with the classic manifestations of DC and the other UPN# 284.001 presenting with progressive bone marrow failure but no other clinical features suggestive of DC. In both patients the telomeres measured in peripheral blood mononuclear cells were very short, being defined as being below the 1st percentile. Mutation analysis in the genes associated with DC revealed that patient 199.001 was homozygous for a novel TERT (C2110T) gene mutation, causing an amino acid change (P704S) within the RT domain of TERT. Both parents were heterozygous for the C to T transition. Interestingly however, the father was in addition heterozygote for a second mutation in TERT (C1234T; H412Y) a mutation which has previously been described and has been shown to reduce telomerase activity by 50%. Investigations of the family revealed that the parent’s were distantly related, explaining the same TERT sequence alteration in both parents. Both arms of the family contained members with pulmonary fibrosis. In the second patient 284.001 we identified two different novel TERT gene mutations. One A2537G causes the amino acid change Y846C in the RT domain of TERT whereas the other C2628G causes H876Q also in the RT domain. One of the mutations was inherited from each parent and the parent with the A2537G mutation also had very short telomeres. These two families illustrate that the pattern of inheritance in patients with DC may be complex and show for the first time that homozygous or compound heterozygous TERT gene mutation may be associated with DC. Co-dominance of the three different TERT gene mutations and the inheritance of short telomeres have possibly contributed to development of disease in these patients who were thought to have sporadic DC and idiopathic aplastic anemia.

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