Characterizing Dyskeratosis Congenita Caused By Parn Mutations in the Zebrafish

Inherited bone marrow failure syndromes (IBMFs) are a group of rare genetic disorders characterized by deficient hematopoiesis and extra-hematologic traits. Most known entities are related to a specific gene or group of genes, but others still remain unclassified. In many cases, the involved proteins are required for critical processes involved in cell survival, such as ribosome biogenesis, maintenance of telomere length, and DNA repair. Importantly, patients with IBMFs have higher risks of developing a variety of cancers from leukemia to solid tumours of the head and neck. In 2015, we published four patients from three different families with mutations in the Poly(A)-specific ribonuclease (PARN) gene. This gene encodes a ribonuclease which is involved in degradation of the poly(A) tails, which regulate mRNA turnover, and thus gene expression. Three of the patients presented with several degrees of mental illness and/or developmental delay. The fourth patient, harbored both a monoallelic deletion and a point mutation at the catalytic domain of the protein, and presented with bone marrow failure and hypomyelination, similar to a severe form of dyskeratosis congenital (DC) known as Hoyeraal-Hreidarsson syndrome. In the last two decades, zebrafish (Danio rerio) has emerged as an excellent animal model for human disease, and is especially relevant in hematology, since many of the transcription factors and cell types are highly conserved. Zebrafish have a single PARN ortholog,with 64% sequence identity to the human gene. Using CRISPR-Cas9 genome editing and a combination of six sgRNAs, we generated a 1.2 kb deletion in the zebrafish parn ortholog extending from exon 5 to 13, causing a premature stop codon. Homozygous fish were generated by incrossing to replicate the complete loss-of-function observed in the patient with the DC-like phenotype. Using whole-mount in situ hybridization (WISH) at 48 hours post-fertilization (hpf), we observed a decrease in the number of several mature myeloid cell lineages including neutrophils (labeled with mpx; p<0.0001), macrophages (lcp1; p=0.0005) and mast cells (cpa5; p=0.0005). We also observed a decrease in the amount of hemoglobin (o-dianisidine staining; p<0.0001). However, the number of hematopoietic stem cells (HSCs) was unchanged in parn mutants. This data parallels similar findings using parn directed splice site and translation start site morpholinos. PARN is described as a protein involved in RNA processing, but has also been associated with telomere maintenance. This latter process is crucial for cell senescence and genome integrity, and is a known cause of several IBMFSs. The telomerase ribonucleoprotein complex is highly active in hematopoietic stem and progenitor cells (HSPCs) and plays a role in cell differentiation. This complex is composed of a reverse transcriptase (TERT), RNA template (TERC), and the dyskerin protein complex (DKC1), mutations of which represent a common cause of DC. qPCR analysis in zebrafish parn mutants revealed a 2.98-fold reduction in tert expression compared with the wild type fish. Combined, these findings suggest that PARN plays an important role in HSC differentiation into myeloid and erythroid lineages, resulting in a bone marrow failure phenotype. Our model provides a unique in vivo platform to study the role of PARN in hematopoiesis and for identifying compounds that restore normal blood cell ratios, which may have the potential to prevent future leukemic transformation. Disclosures No relevant conflicts of interest to declare.

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23 Years of Management: A Retrospective Review of Treatment for Aplastic Anemia.

Blood ◽

10.1182/blood.v114.22.1091.1091 ◽

2009 ◽

Vol 114 (22) ◽

pp. 1091-1091

Author(s):

Connie M Piccone ◽

Marie Boorman Martin ◽

Zung Vu Tran ◽

Kim Smith-Whitley

Keyword(s):

Bone Marrow ◽

Aplastic Anemia ◽

Retrospective Review ◽

Pediatric Patients ◽

Conflicts Of Interest ◽

Bone Marrow Failure ◽

Complete Response ◽

Primary Objective ◽

Hematopoietic Stem ◽

Transfusion Independence

Abstract Abstract 1091 Poster Board I-113 Introduction Aplastic anemia (AA) is a syndrome of bone marrow failure characterized by peripheral pancytopenia and marrow hypoplasia. In the past, AA was considered to be a fatal disease; however, current therapies, including bone marrow transplantation or immunosuppressive therapy (IST) with antithymocyte globulin (ATG) and cyclosporine (CSA), are curative in the majority of patients. IST is effective at restoring hematopoietic stem cell production, but relapse and evolution to myelodysplastic syndromes remain clinical challenges. Additionally, there is no real consensus regarding optimal CSA levels, duration of CSA treatment, or the optimal use of growth factors and their relationship to the development of clonal disease. Objectives The primary objective was to review treatment management for severe AA in pediatric patients in order to elucidate treatment differences and review morbidity and mortality as they relate to treatment variation. Study Design/Methods A retrospective review of pediatric patients treated at the Children's Hospital of Philadelphia for AA (both severe and moderate) over a 23 year period was performed. Results A total of 70 patients with AA were treated at our institution from 1985 to July 2008. Exclusions included: 6 patients who received some type of initial treatment at outside institutions, 4 patients who had missing records, and 2 patients who had a diagnosis of moderate AA. Thus, a total of 58 patient records were included in the analysis. Of the total patients reviewed, 60% were male and 40% were female. 34.5% of patients were African-American, and 57% were diagnosed in 2000 or later. The mean age at diagnosis was 9.5±5.8 years. 52% fell into the category of very severe AA based on published diagnostic criteria, 45% had severe AA, and 2 patients (3%) had moderate AA. 15.5% of patients developed AA in the setting of acute hepatitis. More than half of the patients treated with IST had a complete response (CR). The average time to CR was 15±15 months. Average duration of CSA treatment was 15±13 months and 8.6±10.7 months for growth factor. Two patients (3.5%) died, one from complications unrelated to AA and one from infectious complications post-BMT after initial IST failure. Average time to transfusion independence for all patients was 8±11 months (with a range of 0-54 months). Not surprisingly, the time to transfusion independence was significantly associated with IST failure (p=0.010). Patients who failed treatment had an average time to transfusion independence of 17±16 months as compared to those who were complete responders who had an average time to transfusion independence of 3±3 months. Additionally, there was a significant association between IST failure and CSA levels (p=0.014). Patients who had nontherapeutic CSA levels overall had an increased rate of treatment failure. Of those patients who were nontherapeutic, 56% were noncompliant with CSA administration. There was no significant association between IST failure and bone marrow cellularity (p=0.251). PNH was diagnosed in 5% of patients; there were no patients with evidence of myelodysplastic syndrome (MDS). Two of the 3 patients with PNH failed initial IST. Another 2 patients had evidence of a cytogenetic abnormality (16q deletion), but never progressed to MDS. (Note: averages presented as mean±SD) Conclusions/Methods With current IST regimens, AA is curative in the majority of pediatric patients. IST failure was associated with nonadherence to CSA treatment. For patients with confirmed clonal disease, it is possible that IST failure and the ultimate development of clonal disease are related. Disclosures No relevant conflicts of interest to declare.

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Bone Marrow Failure with 13q Deletion: A Distinct Clinicopathological Entity with Immune Pathophysiology,

Blood ◽

10.1182/blood.v118.21.3420.3420 ◽

2011 ◽

Vol 118 (21) ◽

pp. 3420-3420

Author(s):

Kohei Hosokawa ◽

Takamasa Katagiri ◽

Naomi Sugimori ◽

Ken Ishiyama ◽

Yumi Sasaki ◽

...

Keyword(s):

Bone Marrow ◽

Conflicts Of Interest ◽

Bone Marrow Failure ◽

Survival Rates ◽

Snp Array ◽

Normal Karyotype ◽

Genetic Alterations ◽

Fish Analysis ◽

Hematopoietic Stem ◽

Who 2008

Abstract Abstract 3420 Background: Numerical karyotypic abnormalities such as −7/del(7q) and del(13q) are occasionally seen in patients with bone marrow (BM) failure who do not have typical signs of myelodysplasia. The WHO 2008 defined this subset of BM failure as MDS-U because of its likely association with a risk of evolving into leukemia, while the presence of isolated abnormalities including +8, del(20q), and -Y was not considered to be presumptive evidence of MDS. Previous studies showed that BM failure patients with del(13q) responded to immunosuppressive therapy (IST) and had a favorable prognosis (Ishiyama K et al, Br J Haematol; 117: 747. 2002; Sloand, JCO 2010). However, the clinical features of del(13q) BM failure remain unclear due to its low incidence as well as the frequently associated karyotypic abnormalities. Objectives/Methods: To characterize the clinicopathological features of patients with BM failure with del(13q), this study reviewed the clinical data of 1705 BM failure patients (733 with AA, 286 with MDS-RCUD, 149 with RCMD, 60 with MDS-U) whose blood was examined for the presence of glycosylphosphatidyl-inositol anchored protein (GPI-AP)-deficient granulocytes and erythrocytes from May 1999 through July 2010. Genomic DNA was isolated from the peripheral blood cells of 7 patients with 13q- and was subjected to SNP array-based genome-wide analysis for genetic alterations using GeneChip® 250K arrays to identify the gene locus that is commonly deleted as a result of 13q-. Results: The 13q- clone was found in 25 (1.5%) of the 1705 patients. All the 13q- patients were classified as MDS-U, due to the absence of significant dysplasia to fulfill the criteria for MDS defined by the WHO 2008 classification. BM was hypocellular in 17 patients and normocellular in 6. Seventeen patients had a clone with 13q- alone, while the remaining 8 patients had a clone with 13q- and other numerical abnormalities including –Y, +mar in 2, and −20, del(7q), +8, der(1;7) in 1. A significant increase in the percentage of GPI-AP- granulocytes was detected in 366 (50%) of 733 patients with AA and 115 (23%) of 495 patients with MDS. GPI-AP- cells were detected in all (100%) of the 17 patients with 13q- alone. On the other hand, the prevalence of increased GPI-AP− cells in patients with 13q- plus other abnormalities and in those with the normal karyotype was 38% (3/8) and 43% (405/937), respectively. Fifteen patients with 13q- alone were treated with IST (ATG + cyclosporine in 6 and cyclosporine ± anabolic steroid in 9) and all of them achieved either a PR or a CR, while in the patients with 13q- plus other abnormalities, the response rate to IST was 40%. A total of 106 patients with the normal karyotype were treated with ATG+CsA (48) or CsA±AS (58) and the response rates were 73% and 85%, respectively. None of the 17 13q- patients progressed to advanced MDS or AML during the follow-up period of 3 to 108 months (median: 52 months) while 2 of 8 patients with 13q- plus other abnormalities developed AML. The 5-year overall survival rates of the patients with 13q-, those with 13q- plus other abnormalities, and patients with a normal karyotype were 84%, 45%, and 91%, respectively. The percentage of 13q- clones increased in 5 patients, and decreased in 3 patients after successful IST. When GPI-AP- and GPI-AP+ granulocytes were subjected to a FISH analysis using a 13q probe (13q14.3), the 13q- clones were detected only in of GPI-AP+ granulocytes, suggesting that 13q- cells are derived from non-PIG-A mutant HSCs. SNP arrays identified 13q13.3 to 13q14.3 regions in all cases. Conclusions: MDS-U with 13q- is a benign BM failure syndrome characterized by a good response to IST and a markedly high prevalence of GPI-AP cells. Patients with this type of BM failure may be inappropriately treated with hypomethylating agents or hematopoietic stem cell transplantation from unrelated donors, which is associated with high therapy-related mortality. Therefore, del(13q) should be eliminated from the intermediate prognosis group defined by the IPSS, and BM failure with del(13q) should be managed as idiopathic AA. Disclosures: No relevant conflicts of interest to declare.

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Profilin 1 Is Essential for Retention and Metabolism of Hematopoietic Stem Cells in Bone Marrow

Blood ◽

10.1182/blood.v120.21.1224.1224 ◽

2012 ◽

Vol 120 (21) ◽

pp. 1224-1224

Author(s):

Junke Zheng ◽

Chengcheng Zhang

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Conflicts Of Interest ◽

Bone Marrow Failure ◽

Actin Binding ◽

Wild Type ◽

Cell Fates ◽

Hematopoietic Stem ◽

Multiple Cell

Abstract Abstract 1224 How stem cells interact with the microenvironment to regulate their cell fates and metabolism is largely unknown. Here we show that, in a hematopoietic stem cell (HSC) -specific inducible knockout model, the cytoskeleton-modulating protein profilin 1 (pfn1) is essential for the maintenance of multiple cell fates and metabolism of HSCs. The deletion of pfn1 in HSCs led to bone marrow failure, loss of quiescence, increased apoptosis, and mobilization of HSCs in vivo. In reconstitution analyses, pfn1-deficient cells were selectively lost from mixed bone marrow chimeras. By contrast, pfn1 deletion did not significantly affect differentiation or homing of HSCs. When compared to wild-type cells, levels of expression of Hif-1a, EGR1, and MLL were lower and an earlier switch from glycolysis to mitochondrial respiration with increased ROS level was observed in pfn1-deficient HSCs. This switch preceded the detectable alteration of other cell fates. Importantly, treatment of pfn1-deficient mice with the antioxidant N-acetyl-l-cysteine reversed the ROS level and loss of quiescence of HSCs, suggesting that pfn1 maintained metabolism is required for the quiescence of HSCs. Furthermore, we demonstrated that expression of wild-type pfn1 but not the actin-binding deficient or poly-proline binding-deficient mutants of pfn1 rescued the defective phenotype of pfn1-deficient HSCs. This result indicates that actin-binding and proline-binding activities of pfn1 are required for its function in HSCs. Thus, pfn1 plays an essential role in regulating the retention and metabolism of HSCs in the bone marrow microenvironment. Disclosures: No relevant conflicts of interest to declare.

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G-CSF Treatment Induces Toll-Like Receptor Signaling and Regulates Hematopoietic Stem Cell Function

Blood ◽

10.1182/blood.v122.21.1181.1181 ◽

2013 ◽

Vol 122 (21) ◽

pp. 1181-1181 ◽

Cited By ~ 1

Author(s):

Laura G. Schuettpelz ◽

Joshua N. Borgerding ◽

Priya Gopalan ◽

Matt Christopher ◽

Molly Romine ◽

...

Keyword(s):

Bone Marrow ◽

Cell Function ◽

Conflicts Of Interest ◽

Bone Marrow Failure ◽

Intestinal Flora ◽

Enrichment Analysis ◽

Gene Set Enrichment Analysis ◽

Tlr Signaling ◽

Hematopoietic Stem

Abstract Recent studies demonstrate that inflammatory signals regulate hematopoietic stem cells (HSCs). Granulocyte-colony stimulating factor (G-CSF) is often induced with infection and plays a key role in the stress granulopoiesis response. However, its effects on HSCs are unclear. Herein, we show that treatment with G-CSF induces expansion and increased quiescence of phenotypic HSCs, but causes a marked, cell-autonomous HSC repopulating defect. RNA profiling and flow cytometry studies of HSCs from G-CSF treated mice show that multiple toll- like receptors (TLRs) are upregulated in HSCs upon G-CSF treatment, and gene set enrichment analysis shows enhancement of TLR signaling in G-CSF-treated HSCs. G-CSF-induced expansion of phenotypic HSCs is reduced in mice lacking the TLR signaling adaptors MyD88 or Trif, and the induction of quiescence is abrogated in mice lacking these adaptors. Furthermore, loss of TLR4 mitigates the G-CSF-mediated HSC repopulating defect. Interestingly, baseline HSC function is also dependent on TLR signaling. We show that HSC long-term repopulating activity is enhanced in Tlr4-/- and MyD88-/- mice, but not Trif-/- mice. One potential source of TLR ligands affecting HSC function in the bone marrow is the gut microbiota. Indeed, we show that in mice treated with antibiotics to suppress intestinal flora, G-CSF induced HSC quiescence and hematopoietic progenitor mobilization are attenuated. Moreover, in germ free mice, HSC long-term repopulating activity is enhanced. Collectively these data suggest that low level TLR agonist production by commensal flora contributes to the regulation of HSC function and that G-CSF negatively regulates HSCs, in part, by enhancing TLR signaling. Our finding of enhanced TLR signaling upon G-CSF treatment, and the mitigation of G-CSF’s effects in mice deficient for TLR signaling or commensal organisms, suggest that TLR antagonists and/or agonists may ultimately be used clinically to enhance engraftment following bone marrow transplantation or applied toward the treatment of patients with bone marrow failure. Disclosures: No relevant conflicts of interest to declare.

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Premature Senescence in Hematopoietic Stem and Progenitor Cells in Ribosomopathy-Associated Bone Marrow Failure Syndromes

Blood ◽

10.1182/blood.v126.23.298.298 ◽

2015 ◽

Vol 126 (23) ◽

pp. 298-298

Author(s):

Hengjun Chao ◽

Johnson M. Liu

Keyword(s):

Bone Marrow ◽

Dna Damage ◽

Ribosome Biogenesis ◽

Bone Marrow Failure ◽

Premature Senescence ◽

Hematopoietic Stem ◽

Cycle Arrest ◽

Bone Marrow Failure Syndromes ◽

P53 Activation ◽

Adult Bone

Abstract Introduction: Aged hematopoietic stem cells (HSCs) are known to functionally decline and are prone to development of myeloid malignancies. Recent work has highlighted the twin roles of replication stress and decreased ribosome biogenesis as drivers for the accumulation of DNA damage and senescence. Certain bone marrow failure syndromes, including Shwachman-Diamond syndrome (SDS), Diamond-Blackfan anemia (DBA), and the acquired 5q- syndrome, are characterized by defects in ribosome biogenesis. Furthermore, recent work has suggested a role for p53 activation, through the 5S ribonucleoprotein particle (RNP), in driving cells to senescence following perturbation of ribosome biogenesis. Methods and Results: Here, we have used multiplexing flow cytometry protocols to define, enumerate, and characterize hematopoietic cells of distinct differentiation stages and lineages in 2 DBA cord bloods and 4 adult bone marrows (2 SDS, 1 DBA, and 1 patient with a diminutive somatic deletion of 5q: ages 27, 32, 40, and 30, respectively), as compared with 4 normal cord bloods and 6 normal adult bone marrows. We included a patient with bona fide MDS (diminutive somatic deletion of 5q including RPS14 in a young adult) to compare with the SDS and DBA patients, who do not meet criteria for MDS. Our preliminary results revealed significant defects in the primitive HSC and multipotent progenitor (MPP) compartments in both DBA and SDS. Specifically, we found in DBA and SDS bone marrow and cord blood samples (compared to normal controls): significantly decreased numbers of primitive HSCs (Lin-CD34+CD133+CD38-CD45RA-CD49f+CD90+) and MPPs (Lin-CD34+CD133+CD38-CD45RA-CD49f-CD90-); increased levels of apoptosis and dysregulated proliferation; and G0-1/S cell cycle arrest. We also found significant increases in senescence-associated β-galactosidase staining and G0-1/S cell cycle arrest in Lin-CD34+ and Lin-CD34+CD38-CD133+ subpopulations in all 4 adult patient bone marrows, as compared with normal adult bone marrows processed in identical fashion [see Fig. 1 for representative data from Lin-CD34+CD133+ hematopoietic progenitor cells (HPCs) from one SDS patient]. Foci of the phosphorylated form of the variant histone H2AX (γH2AX) mark DNA damage, and γH2AX staining was similarly increased in comparison to controls (Fig. 1). The mechanism whereby disturbed ribosome biogenesis induces senescence has been suggested as involving 5S RNP-mediated p53 activation. However, our experiments did not demonstrate increased levels of p53 in the SDS patient marrows, as assessed by intracellular staining. Levels of p16, a well known marker of senescence, were markedly increased in the SDS patient samples, when compared to controls. Finally, in the 2 DBA cord bloods analyzed, there was increased senescence-associated β-galactosidase staining but to a lesser degree than in the adult bone marrow samples (as might be expected with temporal progression). Discussion: Taken together, our data suggest that ribosomopathies (which often present in childhood) are disorders of premature senescence. Consequent DNA damage accumulation and decreased repair and compensation may account for the development of MDS and acute myeloid leukemia, disorders seen in young ribosomopathy patients that ordinarily are rare in the general pediatric and young adult population. Disclosures No relevant conflicts of interest to declare.

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Utility of Telomere in Diagnosis of Bone Marrow Failure Syndromes

Blood ◽

10.1182/blood.v126.23.4793.4793 ◽

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.

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Excelent Option Therapy of BONE Marrow Failure in Fanconi Anemia Patients Withouth Full Match Donnor

Blood ◽

10.1182/blood.v128.22.5075.5075 ◽

2016 ◽

Vol 128 (22) ◽

pp. 5075-5075 ◽

Cited By ~ 1

Author(s):

Lisandro L Ribeiro ◽

Samantha Nichele ◽

marco Antonio Bitencourt ◽

Ricardo Petterle ◽

Gisele Loth ◽

...

Keyword(s):

Bone Marrow ◽

Conflicts Of Interest ◽

Bone Marrow Failure ◽

Hematological Parameters ◽

Severe Neutropenia ◽

Cell Transplant ◽

Variable Degree ◽

Duration Of Treatment ◽

Hematopoietic Stem ◽

Hematological Response

Abstract The main cause of morbidity and mortality of FA pts is bone marrow failure (BMF), which usually arises in the first decade of life and progresses to transfusion dependence and severe neutropenia. Androgen treatment has been recommended for FA pts with BMF for whom there is no acceptable hematopoietic stem cell transplant donor. Oxymetholone and Danazol are frequently used in these pts. We retrospectively analyzed data on 67 FA pts who received oxymetholone or danazol for the treatment of their BMF. The starting dose was approximately 1mg/kg for oxy and 2-4mg/kg for danazol. The hematological parameters at the initiation of treatment were hemoglobin (Hb) < 8 g/dL and/or thrombocytes < 30.000/μl. Patients were diagnosed between 01.2005 and 01.2016. The median age was 10.5 ys (2.9 - 40ys). Gender: 39M/27F. The median duration of treatment was 18m (3m - 95m). Fifty-three patients (79%) showed hematological response and became transfusion independence at a median of 3 months after beginning oxymetholone (2-9m) and 5 months after danazol (4-7m). Two adult pts treated with danazol achieved total hematological response with 2.5mg/kg. Seven pts are stable after tapering and stopping androgen with a median follow up of 4 ys (6m-8.5ys). Fourteen pts did not respond to treatment (21%). Eleven pts received an HSCT and seven are alive and well. Three pts were not transplanted and two are alive but transfusion dependent and one pt died from CNS bleeding. All patients developed variable degree of virilization but it was more evident with oxymetholone therapy. Older age at starting therapy was related to less virilization. Conclusion: This study shows the largest number of FA pts treated with androgen up till now. Androgen is an effective and well-tolerated treatment option for FA pts who develop BMF with 79% of them showing transfusion free after 3-5 months. This response may give us time to search for better donors. Disclosures No relevant conflicts of interest to declare.

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Diagnostic utility of telomere length measurement in a hospital setting

10.1101/225797 ◽

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.

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Activation of Non-Canonical Immune Signalling Pathways Drives Marrow Failure in a Murine Model of MDS

Blood ◽

10.1182/blood.v124.21.3246.3246 ◽

2014 ◽

Vol 124 (21) ◽

pp. 3246-3246

Author(s):

Rawa Ibrahim ◽

Joanna Wegrzyn ◽

Linda Ya-Ting Chang ◽

Patricia Umlandt ◽

Jeff Lam ◽

...

Keyword(s):

Bone Marrow ◽

Stem Cell ◽

Cell Line ◽

Conflicts Of Interest ◽

Bone Marrow Failure ◽

Signalling Pathway ◽

Gene Set Enrichment Analysis ◽

Mouse Bone Marrow ◽

Bone Marrow Niche ◽

Hematopoietic Stem

Abstract The Myelodysplastic Syndromes (MDS) are the most common hematological malignancies arising from stem/progenitor cells. MDS is characterized by ineffective hematopoiesis in one or more lineages of the bone marrow, resulting in peripheral cytopenias and the propensity to progress to either acute myeloid leukemia (AML) or bone marrow failure (BMF). The most common cytogenetic aberration associated with MDS is deletion of the long arm of chromosome 5. Many of the molecular events involved in the development of del(5q) MDS have been elucidated including haploinsufficiency of the gene encoding the ribosomal protein RPS14, responsible for the anemia observed, and haploinsufficency of the miRNAs miR-145 and miR-146a, which together target the innate immune signaling pathway, specifically, the Toll-like receptor-4 (TLR-4)signalling pathway. It has been demonstrated that overexpression of a target of miR-146a,TRAF6, in mouse bone marrow can recapitulate the phenotype of del(5q) MDS including the cytopenias and progression to BMF or AML. However, enforced expression of TIRAP, a miR-145 target gene, results in rapid BMF independent of TRAF6. The molecular and cellular mechanisms responsible for the differential outcome of overexpression of two genes that act within the same signalling pathway remain to be fully understood. We have identified several differentially expressed cytokines, including interferon gamma (IFNγ) and interleukin-10 (IL-10), following TIRAP overexpression compared with TRAF6 overexpression. Promoter methylation analysis has shown hypermethylation of key adaptors and signal transducers that lie between TIRAP and TRAF6 in the TLR-4 signalling pathway, suggesting activation of different pathways by TIRAP and TRAF6 overexpression. Indeed, blockade of TRAF6 and MyD88 did not inhibit TIRAP induced expression of these cytokines, suggesting that IFNγ and IL-10 production occurs in a TRAF6 and MyD88 independent manner. We identified IFNγ as the critical effector cytokine responsible for TIRAP mediated marrow failure. Gene set enrichment analysis has shown an enrichment of an IFNγ signature in MDS patients with a low risk of transformation to AML compared to healthy controls. Furthermore, interferon signatures were highly enriched in MDS patients compared to patients with AML, suggesting an important role for IFNγ signaling in driving MDS progression toward marrow failure as opposed to leukemic progression. IFNγ has been shown to inhibit components of the bone marrow niche by blocking RANK signalling in stromal cells such as osteoclast progenitors. Using coculture of TIRAP expressing bone marrow cells with the RAW264.7 monocyte cell line, a cell line that is capable of differentiation into osteoclasts, we found an inhibition in the ability of these cells to form osteoclasts compared to control. This provides the first line of evidence suggesting that immune signalling defects arising from genetic perturbations in the hematopoietic stem cell compartment can result in stem cell niche dysfunction leading to marrow failure. Disclosures No relevant conflicts of interest to declare.

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Conditional TRF1 Knockout in Haematopoietic Progenitor Cells Causes Telomere Shortening and Bone Marrow Failure by Induction of Cellular Senescence

Blood ◽

10.1182/blood.v118.21.49.49 ◽

2011 ◽

Vol 118 (21) ◽

pp. 49-49

Author(s):

Fabian Beier ◽

Miguel Foronda ◽

Jose A Palacios ◽

Paula Martinez ◽

Maria A Blasco

Keyword(s):

Bone Marrow ◽

Progenitor Cells ◽

Bone Marrow Cells ◽

Conflicts Of Interest ◽

Bone Marrow Failure ◽

Conditional Knockout ◽

Telomere Maintenance ◽

Loss Of Function ◽

Telomere Shortening ◽

Exon 1

Abstract Abstract 49 Introduction: Mutations in the telomerase complex may cause bone marrow failure syndromes due to loss-of-function and consecutive telomere shortening. In addition to the telomerase complex, the six “shelterin” proteins (TRF1, TRF2, TIN2, RAP1, POT1 and TPP1) are required for telomere maintenance. TRF1 has a prominent role in chromosome capping function and prevents the recognition of telomeres by DNA repair mechanisms. At the moment, only TIN2 mutations have been linked to bone marrow failure. Here we aimed to identify other shelterin proteins might cause bone marrow failures. A previous study reported an clinical association between TRF1 mutations and acquired aplastic anemia, however the proof-of-principle that TRF1 can cause bone marrow failure is still missing (Savage SA Exp Hematol 2006). Material and Methods: To address this issue, we used the Mx1-Cre system in combination with the recently generated TRF1 allele in which the exon 1 of TRF1 is flanked by floxP (Martinez P Gen Dev 2009). The bone marrow of the bitransgenic mice was transplanted into B6 wildtype mice and poly (P:I) injections allowed the conditional knockout of TRF1. Results: Initiation of poly (P:I) injections 4 weeks after transplantation resulted in a failure of all three haematopoietic lineages after 17 days and histopathology revealed massive hypocellular bone marrow consistent with a bone marrow failure. Transplanted control animals showed normal histopathology and even increased neutrophil and thrombocyte counts. Further detailed FACS analysis 7 days after initiation of poly (P:I) injections showed a significant depletion of common myeloid, megakaryocte-erythocyte and common lymphoid progenitor cells, but only a slight decrease of lin-, c-kit+,Sca-1+ haematopoietic stem cells. Interesting, we found no increased rate of apoptosis for the decrease of the progenitor cells, but ß-galactosidase staining showed significant higher amounts of senescent cells in the bone marrow. Further detailed analysis of FACS sorted bone marrow cells showed that especially the c-kit positive progenitor fraction underwent senescence and cell cycle analysis showed an increased G2-M phase indicating a G2-M arrest. In line with these findings RT-PCR of FACS sorted BM revealed increased levels of p21 in the c-kit positive fraction. In addition BrdU injections into the mice on day 7 after poly (P:I) initiation showed increased incorporation and telomere length analysis of transplanted animals with and without poly (P:I) injections revealed massive telomere shortening on day 17. Conclusions: Our data indicates that TRF1 knockout especially affects haematopoietic progenitor cells by inducing G2-M arrest, induction of p21, and subsequent senescence. Further, compensation of the progenitor cell depletion leads to higher cell turnover and consecutively massive telomere shortening. Taken together this is the first report proving that TRF1 can cause a bone marrow failure and is accompanied with significant telomere shortening. Disclosures: No relevant conflicts of interest to declare.

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