Telomere Elongation in Dyskeratosis Congenita Induced Pluripotent Stem Cells.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 497-497
Author(s):  
Suneet Agarwal ◽  
Yuin-Han Loh ◽  
Erin M McLoughlin ◽  
Junjiu Huang ◽  
In-Hyun Park ◽  
...  

Abstract Abstract 497 Patients with dyskeratosis congenita (DC), a disorder of telomere maintenance, suffer premature degeneration of multiple tissues. Bone marrow failure is the principal cause of mortality, and allogeneic stem cell transplantation is limited by increased treatment-related mortality. Somatic cells can be reprogrammed using defined genetic and chemical factors, yielding “induced pluripotent stem” (iPS) cell lines which have the capacity to differentiate into any tissue. Patient-specific iPS cells therefore hold promise as therapeutic agents and disease models for human degenerative disorders like DC. A cardinal feature of iPS cells is acquisition of indefinite self-renewal capacity, and we have found that telomere length is increased in human iPS cells relative to the normal primary somatic cells from which they are derived. Here we investigated whether defects in telomerase function would limit derivation or self-renewal of iPS cells from patients with DC. We reprogrammed primary fibroblasts from patients with X-linked and autosomal dominant DC, caused by mutations in the genes encoding dyskerin and telomerase RNA component (TERC), respectively. We were able to establish multiple DC-specific iPS lines showing all hallmarks of pluripotency, including the formation of hematopoietic progenitors in vitro. Unexpectedly, DC-specific iPS cells were able to sustain continual proliferation in vitro, in contrast to the premature senescence displayed by the DC fibroblasts. Although early passage DC iPS cells had shorter telomeres than donor fibroblasts, we found that telomere length in DC iPS cells increased with continued passage in culture. To explain this finding, we discovered that steady state levels of TERC, which are critically limiting in several forms of DC, are upregulated in normal and DC iPS cells. We found that TERC upregulation is a feature of the pluripotent state, that the TERC locus is a target of pluripotency-associated transcription factors, and that transcriptional silencing accompanies a 3' deletion at the TERC locus in autosomal dominant DC. Our results demonstrate that reprogramming restores self-renewal capacity in DC cells despite genetic lesions affecting telomerase, and suggest that strategies to enhance endogenous TERC expression may be feasible and therapeutically beneficial in DC patients. The studies demonstrate the value of patient-specific iPS cells for basic and translational discovery, and further the rationale for autologous iPS based cellular therapy of genetic hematologic disorders. Disclosures: Daley: MPM Capital: Consultancy; Solasia: Consultancy; Epizyme: Consultancy; iPierian: Consultancy, Equity Ownership.

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 50-50
Author(s):  
Baiwei Gu ◽  
Jason A. Mills ◽  
Jian-meng Fan ◽  
Deborah L. French ◽  
Monica Bessler ◽  
...  

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.


2009 ◽  
Vol 390 (9) ◽  
Author(s):  
Alexandra Rolletschek ◽  
Anna M. Wobus

Abstract Adult cells have been reprogrammed into induced pluripotent stem (iPS) cells by introducing pluripotency-associated transcription factors. Here, we discuss recent advances and challenges of in vitro reprogramming and future prospects of iPS cells for their use in diagnosis and cell therapy. The generation of patient-specific iPS cells for clinical application requires alternative strategies, because genome-integrating viral vectors may cause insertional mutagenesis. Moreover, when suitable iPS cell lines will be available, efficient and selective differentiation protocols are needed to generate transplantable grafts. Finally, we point to the requirement of a regulatory framework necessary for the commercial use of iPS cells.


2011 ◽  
Vol 29 (27_suppl) ◽  
pp. 227-227
Author(s):  
S. M. L. Lim ◽  
I. Aksoy ◽  
K. G. C. Lim ◽  
J. Karuppasamy ◽  
U. Divakar ◽  
...  

227 Background: Recent advances in pluripotent stem cell biology offer patient-specific disease models to investigate in vitro mechanisms of tumorigenesis. Induced pluripotent stem (iPS) cells were originally derived by reprogramming of human dermal fibroblasts through ectopic expression of pluripotency–associated transcription factors. A limitation to the use of dermal fibroblasts as the starting cell type for reprogramming is that it usually takes weeks to expand cells from a single biopsy, and the efficiency of the process is very low. In contrast, a large number of adipose-derived mesenchymal stromal cells (Ad-MSCs) can be easily obtained from the stroma of human breast tissue, without the time-consuming steps of cell expansion. Here we investigated the ability to induce pluripotency in committed, Ad-MSCs derived from the stroma of breast tissue. Methods: The aim of this study is to investigate the potential of using Ad-MSCs derived from surgically discarded breast stromal tissue to generate human iPS. Discarded tissue during surgical procedures was processed in vitro and Ad-MSCs were derived. These Ad-MSCs were then used to generate iPS cells by ectopic expression of “Yamanaka’s cocktail” containing OCT4, SOX2, KLF4 and c-MYC. Results: The success rate in generating iPS cells from human Ad-MSCs derived from breast stromal tissue is very high compared to the use of dermal fibroblasts. In our study, almost all human Ad-MSC cell lines can be reprogrammed into iPS cells, which share the same characteristics as skin fibroblast-derived iPS cells and human embryonic stem cells in their morphology, gene expression profile and differentiation capacities. Conclusions: We are now optimizing this approach and making it more clinically relevant by adopting an integration-free method to deliver the reprogramming factors. The successful reprogramming of breast stromal-derived Ad-MSCs into iPS cells may provide a valuable source of patient-specific iPS cells to study the mechanism of tumorigenesis in patients with breast cancer.


2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Heidrun Steinle ◽  
Marbod Weber ◽  
Andreas Behring ◽  
Ulrike Mau-Holzmann ◽  
Christian Schlensak ◽  
...  

The reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) is gaining in importance in the fields of regenerative medicine, tissue engineering, and disease modeling. Patient-specific iPSCs have as an unlimited cell source a tremendous potential for generating various types of autologous cells. For the future clinical applicability of these iPSC-derived cells, the generation of iPSCs via nongenome integrating methods and the efficient reprogramming of patients’ somatic cells are required. In this study, 2 different RNA-based footprint-free methods for the generation of iPSCs were compared: the use of synthetic modified messenger RNAs (mRNAs) or self-replicating RNAs (srRNAs) encoding the reprogramming factors and GFP. Using both RNA-based methods, integration-free iPSCs without genomic alterations were obtained. The pluripotency characteristics identified by specific marker detection and the in vitro and in vivo trilineage differentiation capacity were comparable. Moreover, the incorporation of a GFP encoding sequence into the srRNA enabled a direct and convenient monitoring of the reprogramming procedure and the successful detection of srRNA translation in the transfected cells. Nevertheless, the use of a single srRNA to induce pluripotency was less time consuming, faster, and more efficient than the daily transfection of cells with synthetic mRNAs. Therefore, we believe that the srRNA-based approach might be more appropriate and efficient for the reprogramming of different types of somatic cells for clinical applications.


2017 ◽  
Vol 58 (4) ◽  
pp. 430-438 ◽  
Author(s):  
Shoki Inui ◽  
Kazumasa Minami ◽  
Emiko Ito ◽  
Hiromasa Imaizumi ◽  
Seiji Mori ◽  
...  

Abstract Induced pluripotent stem (iPS) cells have demonstrated they can undergo self-renewal, attain pluripotency, and differentiate into various types of functional cells. In clinical transplantation of iPS cells, however, a major problem is the prevention of tumorigenesis. We speculated that tumor formation could be inhibited by means of irradiation. Since the main purpose of this study was to explore the prevention of tumor formation in human iPS (hiPS) cells, we tested the effects of irradiation on tumor-associated factors such as radiosensitivity, pluripotency and cell death in hiPS cells. The irradiated hiPS cells showed much higher radiosensitivity, because the survival fraction of hiPS cells irradiated with 2 Gy was < 10%, and there was no change of pluripotency. Irradiation with 2 and 4 Gy caused substantial cell death, which was mostly the result of apoptosis. Irradiation with 2 Gy was detrimental enough to cause loss of proliferation capability and trigger substantial cell death in vitro. The hiPS cells irradiated with 2 Gy were injected into NOG mice (NOD/Shi-scid, IL-2 Rγnull) for the analysis of tumor formation. The group of mice into which hiPS cells irradiated with 2 Gy was transplanted showed significant suppression of tumor formation in comparison with that of the group into which non-irradiated hiPS cells were transplanted. It can be presumed that this diminished rate of tumor formation was due to loss of proliferation and cell death caused by irradiation. Our findings suggest that tumor formation following cell therapy or organ transplantation induced by hiPS cells may be prevented by irradiation.


2008 ◽  
Vol 28 (7) ◽  
pp. 2332-2341 ◽  
Author(s):  
Kalpana Kannan ◽  
Andrew D. L. Nelson ◽  
Dorothy E. Shippen

ABSTRACT Dyskerin binds the H/ACA box of human telomerase RNA and is a core telomerase subunit required for RNP biogenesis and enzyme function in vivo. Missense mutations in dyskerin result in dyskeratosis congenita, a complex syndrome characterized by bone marrow failure, telomerase enzyme deficiency, and progressive telomere shortening. Here we demonstrate that dyskerin also contributes to telomere maintenance in Arabidopsis thaliana. We report that both AtNAP57, the Arabidopsis dyskerin homolog, and AtTERT, the telomerase catalytic subunit, accumulate in the plant nucleolus, and AtNAP57 associates with active telomerase RNP particles in an RNA-dependent manner. Furthermore, AtNAP57 interacts in vitro with AtPOT1a, a novel component of Arabidopsis telomerase. Although a null mutation in AtNAP57 is lethal, AtNAP57, like AtTERT, is not haploinsufficient for telomere maintenance in Arabidopsis. However, introduction of an AtNAP57 allele containing a T66A mutation decreased telomerase activity in vitro, disrupted telomere length regulation on individual chromosome ends in vivo, and established a new, shorter telomere length set point. These results imply that T66A NAP57 behaves as a dominant-negative inhibitor of telomerase. We conclude that dyskerin is a conserved component of the telomerase RNP complex in higher eukaryotes that is required for maximal enzyme activity in vivo.


Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2468-2468 ◽  
Author(s):  
Bai-wei Gu ◽  
Jason A. Mills ◽  
Marisa Apicella ◽  
Jian-meng Fan ◽  
Deborah L. French ◽  
...  

Abstract Telomerase is a ribonucleoprotein that adds telomeric repeats onto the chromosome ends, preventing the replication-dependent loss of telomere repeats and cellular senescence in highly proliferative germ-line cells and in stem cells and cancer cells. Dyskeratosis Congenita (DC) is a rare bone marrow failure syndrome, which affects tissues that need constant renewal by stem cell activity. So far 8 genes have been found whose mutation causes DC and they all encode products that play a role in telomere maintenance. About 35% of DC patients show X-linked-recessive inheritance due to mutations in the DKC1gene encoding dyskerin, a protein important in telomere maintenance and ribosomal RNA biogenesis. Mutant dyskerin can destabilize 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 and some results suggest dyskerin may play a more direct role in telomerase action. So far studies of the cell biology of DC stem 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 both telomere biology and hematopoiesis between mouse and human. In this study, to investigate disease pathogenesis of X-linked DC, we generated induced pluripotent stem cells (iPSC) from patients’ skin fibroblast cell carrying DKC1 mutations Q31E, Δ37 and A353V. The recurrent A353V mutation accounts for about 40% of DKC1 mutations and usually causes a severe clinical phenotype while patients carrying Q31E and Δ37 mutations show a milder phenotype. We found that dyskerin protein expression in all of these dyskerin mutant iPS cells is decreased in agreement with our mouse studies that show mutant proteins are relatively unstable. These iPS cells show dramatically decreased TERC RNA levels and telomerase activity. Telomere length measurement revealed that mutant iPS cells lose the ability to elongate telomeres during the reprogramming processing; telomere erosion was particularly rapid in A353V cells. To further investigate whether dyskerin protein could play direct role in regulating telomerase activity other than stabilization of TERC RNA during the processing of assembly, we tested if the defect in telomerase function in these iPS cells could be rescued by expressing wild type dyskerin or TERC RNA. We expressed the rescuing genes by using the zinc-finger nuclease-mediated method to insert them into the safe harbor AAVs1 site, initially of DKC1Δ37 cells. After testing the telomerase function, we found that expressing WT-dyskerin protein in Δ37 iPS cells fully restores the mature Terc RNA expression level and the telomerase activity to normal levels. However, although Δ37 iPS with over-expressed WT TERC RNA can accumulate normal level of TERC RNA, these cells fail to increase telomerase activity. These results suggest that defective telomerase activity cause by DKC1 mutations can only reversed by expressing WT dyskerin but not by TERC RNA. These data suggest that, as one of three core components of the telomerase complex, dyskerin may play a direct role in telomerase activity. Disclosures: No relevant conflicts of interest to declare.


2017 ◽  
Vol 398 (8) ◽  
pp. 939-954 ◽  
Author(s):  
Jeannine Hoepfner ◽  
Mandy Kleinsorge ◽  
Oliver Papp ◽  
Susanne Alfken ◽  
Robin Heiringhoff ◽  
...  

Abstract The transthyretin protein is thermodynamically destabilised by mutations in the transthyretin gene, promoting the formation of amyloid fibrils in various tissues. Consequently, impaired autonomic organ function is observed in patients suffering from transthyretin-related familial amyloidotic polyneuropathy (FAP). The influence of individual genetic backgrounds on fibril formation as a potential cause of genotype-phenotype variations needs to be investigated in order to ensure efficient patient-specific therapies. We reprogrammed FAP patient fibroblasts to induced pluripotent stem (iPS) cells and differentiated these cells into transthyretin-expressing hepatocyte-like cells (HLCs). HLCs differentiated from FAP iPS cells and healthy control iPS cells secreted the transthyretin protein in similar concentrations. Mass spectrometry revealed the presence of mutant transthyretin protein in FAP HLC supernatants. In comparison to healthy control iPS cells, we demonstrated the formation of transthyretin amyloid fibril-like structures in FAP HLC supernatants using the amyloid-specific dyes Congo red and thioflavin T. These dyes were also applicable for the quantitative determination of in vitro formed transthyretin fibril-like structures. Moreover, we confirmed the inhibition of fibril formation by the TTR kinetic stabiliser diclofenac. Thioflavin T fluorescence intensity measurements even allowed the quantification of amyloid fibril-like structures in 96-well plate formats as a prerequisite for patient-specific drug screening approaches.


Author(s):  
Basak Celtikci ◽  
Gulnihal Kulaksiz Erkmen ◽  
Zeliha Gunnur Dikmen

: Telomeres are the protective end caps of eukaryotic chromosomes and they decide the proliferative lifespan of somatic cells, as the guardians of the cell replication. Telomere length in leucocytes reflects telomere length in other somatic cells. Leucocyte telomere length can be a biomarker of human ageing. The risk of diseases, which are associated with reduced cell proliferation and tissue degeneration, including aging or aging-associated diseases, such as dyskeratosis congenita, cardiovascular diseases, pulmonary fibrosis and aplastic anemia, are correlated with an increase in short telomeres. On the other hand, the risk of diseases, which are associated with increased proliferative growth, including major cancers, is correlated with long telomeres. In most of the cancers, a telomere maintenance mechanism during DNA replication is essential. The reactivation of the functional ribonucleoprotein holoenzyme complex [telomerase] starts the cascade from normal and premalignant somatic cells to advanced malignant cells. Telomerase is overexpressed during the development of cancer and embryonic stem cells, through controlling genome integrity, cancer formation and stemness. Cancer cells have mechanisms to maintain telomeres to avoid initiation of cellular senescence or apoptosis, and halting cell division by critically short telomeres. Modulation of the human telomerase reverse transcriptase is the ratelimiting step for the production of functional telomerase and the telomere maintenance. Human telomerase reverse transcriptase promoter promotes its gene expression only in tumor cells, but not in normal cells. Some cancers activate an alternative lengthening of telomeres maintenance mechanism via DNA recombination to unshorten their telomeres. Not only heritability but also oxidative stress, inflammation, environmental factors, and therapeutic interventions have an effect on telomere shortening, explaining the variability in telomere length across individuals. There have been a large number of publications, which correlate human diseases with progressive telomere shortening. Telomere length of an individual at birth is also important to follow up telomere shortening, and it can be used as biomarkers for healthy aging. On the other hand, understanding of cellular stress factors, which affect stem cell behavior, will be useful in regeneration or treatment in cancer and age-associated diseases. In this review, we will understand the connection between stem cell and telomere biology, cancer, and aging-associated diseases. This connection may be useful for discovering novel drug targets and improve outcomes for patients having cancer and aging-associated diseases.


2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Thekkeparambil Chandrabose Srijaya ◽  
Padmaja Jayaprasad Pradeep ◽  
Rosnah Binti Zain ◽  
Sabri Musa ◽  
Noor Hayaty Abu Kasim ◽  
...  

Induced pluripotent stem cell-based therapy for treating genetic disorders has become an interesting field of research in recent years. However, there is a paucity of information regarding the applicability of induced pluripotent stem cells in dental research. Recent advances in the use of induced pluripotent stem cells have the potential for developing disease-specific iPSC linesin vitrofrom patients. Indeed, this has provided a perfect cell source for disease modeling and a better understanding of genetic aberrations, pathogenicity, and drug screening. In this paper, we will summarize the recent progress of the disease-specific iPSC development for various human diseases and try to evaluate the possibility of application of iPS technology in dentistry, including its capacity for reprogramming some genetic orodental diseases. In addition to the easy availability and suitability of dental stem cells, the approach of generating patient-specific pluripotent stem cells will undoubtedly benefit patients suffering from orodental disorders.


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