51
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Thilagavathi J, Venkatesh S, Dada R. Telomere length in reproduction. Andrologia 2012; 45:289-304. [DOI: 10.1111/and.12008] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/04/2012] [Indexed: 01/22/2023] Open
Affiliation(s)
- J. Thilagavathi
- Laboratory for Molecular Reproduction and Genetics; Department of Anatomy; All India Institute of Medical Sciences; New Delhi; India
| | - S. Venkatesh
- Laboratory for Molecular Reproduction and Genetics; Department of Anatomy; All India Institute of Medical Sciences; New Delhi; India
| | - R. Dada
- Laboratory for Molecular Reproduction and Genetics; Department of Anatomy; All India Institute of Medical Sciences; New Delhi; India
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52
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Teplyuk NM. Near-to-perfect homeostasis: examples of universal aging rule which germline evades. J Cell Biochem 2012; 113:388-96. [PMID: 21928349 DOI: 10.1002/jcb.23366] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Aging is considered to be a progressive decline in an organism's functioning over time and is almost universal throughout the living world. Currently, many different aging mechanisms have been reported at all levels of biological organization, with a variety of biochemical, metabolic, and genetic pathways involved. Some of these mechanisms are common across species, and others work different, but each of them is constitutive. This review describes the common characteristics of the aging processes, which are consistent changes over time that involve either the accumulation or depletion of particular system components. These accumulations and depletions may result from imperfect homeostasis, which is the incomplete compensation of a particular biological process with another process evolved to compensate it. In accordance with disposable-soma theory, this imperfection in homeostasis may originate as a function of cell differentiation as early as in yeasts. It may result either from antagonistic pleiotropy mechanisms, or be simply negligible as a subject of natural selection if an adverse effect of the accumulation phenotypically manifests in organism's post-reproductive age. If this phenomenon holds true for many different functions it would lead to the occurrence of a wide variety of aging mechanisms, some of which are common among species, while others unique, because aging is the inherent property of most biological processes that have not yet evolved to be perfectly in balance. Examples of imperfect homeostasis mechanisms of aging, the ways in which germ line escapes from them, and the possibilities of anti-aging treatment are discussed in this review.
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Affiliation(s)
- Nadiya M Teplyuk
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
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53
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Different telomere-length dynamics at the inner cell mass versus established embryonic stem (ES) cells. Proc Natl Acad Sci U S A 2011; 108:15207-12. [PMID: 21873233 DOI: 10.1073/pnas.1105414108] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Murine embryonic stem (ES) cells have unusually long telomeres, much longer than those in embryonic tissues. Here we address whether hyper-long telomeres are a natural property of pluripotent stem cells, such as those present at the blastocyst inner cell mass (ICM), or whether it is a characteristic acquired by the in vitro expansion of ES cells. We find that ICM cells undergo telomere elongation during the in vitro derivation of ES-cell lines. In vivo analysis shows that the hyper-long telomeres of morula-injected ES cells remain hyper-long at the blastocyst stage and longer than telomeres of the blastocyst ICM. Telomere lengthening during derivation of ES-cell lines is concomitant with a decrease in heterochromatic marks at telomeres. We also found increased levels of the telomere repeat binding factor 1 (TRF1) telomere-capping protein in cultured ICM cells before telomere elongation occurs, coinciding with expression of pluripotency markers. These results suggest that high TRF1 levels are present in pluripotent cells, most likely to ensure proficient capping of the newly synthesized telomeres. These results highlight a previously unnoticed difference between ICM cells at the blastocyst and ES cells, and suggest that abnormally long telomeres in ES cells are likely to result from continuous telomere lengthening of proliferating ICM cells locked at an epigenetic state associated to pluripotency.
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54
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Seo HJ, Lee SK, Baik HW, Cheon YP, Chun TH, Choi IH, Lee KH. Expressional Profiling of Telomerase and Telomere-Associated Molecules in the Rat Testis and Seminal Vesicle during Postnatal Developmental Period. JOURNAL OF ANIMAL SCIENCE AND TECHNOLOGY 2011. [DOI: 10.5187/jast.2011.53.3.195] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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55
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Harley CB, Liu W, Blasco M, Vera E, Andrews WH, Briggs LA, Raffaele JM. A natural product telomerase activator as part of a health maintenance program. Rejuvenation Res 2010; 14:45-56. [PMID: 20822369 DOI: 10.1089/rej.2010.1085] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Most human cells lack sufficient telomerase to maintain telomeres, hence these genetic elements shorten with time and stress, contributing to aging and disease. In January, 2007, a commercial health maintenance program, PattonProtocol-1, was launched that included a natural product-derived telomerase activator (TA-65®, 10-50 mg daily), a comprehensive dietary supplement pack, and physician counseling/laboratory tests at baseline and every 3-6 months thereafter. We report here analysis of the first year of data focusing on the immune system. Low nanomolar levels of TA-65® moderately activated telomerase in human keratinocytes, fibroblasts, and immune cells in culture; similar plasma levels of TA-65® were achieved in pilot human pharmacokinetic studies with single 10- to 50-mg doses. The most striking in vivo effects were declines in the percent senescent cytotoxic (CD8(+)/CD28(-)) T cells (1.5, 4.4, 8.6, and 7.5% at 3, 6, 9, and 12 months, respectively; p = not significant [N.S.], 0.018, 0.0024, 0.0062) and natural killer cells at 6 and 12 months (p = 0.028 and 0.00013, respectively). Most of these decreases were seen in cytomegalovirus (CMV) seropositive subjects. In a subset of subjects, the distribution of telomere lengths in leukocytes at baseline and 12 months was measured. Although mean telomere length did not increase, there was a significant reduction in the percent short (<4 kbp) telomeres (p = 0.037). No adverse events were attributed to PattonProtocol-1. We conclude that the protocol lengthens critically short telomeres and remodels the relative proportions of circulating leukocytes of CMV(+) subjects toward the more "youthful" profile of CMV(-) subjects. Controlled randomized trials are planned to assess TA-65®-specific effects in humans.
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56
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Coussens M, Davy P, Brown L, Foster C, Andrews WH, Nagata M, Allsopp R. RNAi screen for telomerase reverse transcriptase transcriptional regulators identifies HIF1alpha as critical for telomerase function in murine embryonic stem cells. Proc Natl Acad Sci U S A 2010; 107:13842-7. [PMID: 20643931 PMCID: PMC2922273 DOI: 10.1073/pnas.0913834107] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In various types of stem cells, including embryonic stem (ES) cells and hematopoietic stem cells, telomerase functions to ensure long-term self-renewal capacity via maintenance of telomere reserve. Expression of the catalytic component of telomerase, telomerase reverse transcriptase (Tert), which is essential for telomerase activity, is limiting in many types of cells and therefore plays an important role in establishing telomerase activity levels. However, the mechanisms regulating expression of Tert in cells, including stem cells, are presently poorly understood. In the present study, we sought to identify genes involved in the regulation of Tert expression in stem cells by performing a screen in murine ES (mES) cells using a shRNA expression library targeting murine transcriptional regulators. Of 18 candidate transcriptional regulators of Tert expression identified in this screen, only one candidate, hypoxia inducible factor 1 alpha (Hif1alpha), did not have a significant effect on mES cell morphology, survival, or growth rate. Direct shRNA-mediated knockdown of Hif1alpha expression confirmed that suppression of Hif1alpha levels was accompanied by a reduction in both Tert mRNA and telomerase activity levels. Furthermore, gradual telomere attrition was observed during extensive proliferation of Hif1alpha-targeted mES cells. Switching Hif1alpha-targeted mES cells to a hypoxic environment largely restored Hif1alpha levels, as well as Tert expression, telomerase activity levels, and telomere length. Together, these findings suggest a direct effect of Hif1alpha on telomerase regulation in mES cells, and imply that Hif1alpha may have a physiologically relevant role in maintenance of functional levels of telomerase in stem cells.
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Affiliation(s)
- Matthew Coussens
- Institute for Biogenesis Research, University of Hawaii, Honolulu, HI 96813; and
| | - Philip Davy
- Institute for Biogenesis Research, University of Hawaii, Honolulu, HI 96813; and
| | | | | | | | - Melissa Nagata
- Institute for Biogenesis Research, University of Hawaii, Honolulu, HI 96813; and
| | - Richard Allsopp
- Institute for Biogenesis Research, University of Hawaii, Honolulu, HI 96813; and
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57
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Turner S, Wong HP, Rai J, Hartshorne GM. Telomere lengths in human oocytes, cleavage stage embryos and blastocysts. Mol Hum Reprod 2010; 16:685-94. [PMID: 20573647 PMCID: PMC2930518 DOI: 10.1093/molehr/gaq048] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Telomeres are repeated sequences that protect the ends of chromosomes and harbour DNA repair proteins. Telomeres shorten during each cell division in the absence of telomerase. When telomere length becomes critically short, cell senescence occurs. Telomere length therefore reflects both cellular ageing and capacity for division. We have measured telomere length in human germinal vesicle (GV) oocytes and preimplantation embryos, by quantitative fluorescence in situ hybridization (Q-FISH), providing baseline data towards our hypothesis that telomere length is a marker of embryo quality. The numbers of fluorescent foci suggest that extensive clustering of telomeres occurs in mature GV stage oocytes, and in preimplantation embryos. When calculating average telomere length by assuming that each signal presents one telomere, the calculated telomere length decreased from the oocyte to the cleavage stages, and increased between the cleavage stages and the blastocyst (11.12 versus 8.43 versus 12.22 kb, respectively, P < 0.001). Other methods of calculation, based upon expected maximum and minimum numbers of telomeres, confirm that telomere length in blastocysts is significantly longer than cleavage stages. Individual blastomeres within an embryo showed substantial variation in calculated average telomere length. This study implies that telomere length changes according to the stage of preimplantation embryo development.
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Affiliation(s)
- S Turner
- Warwick Medical School, Clinical Sciences Research Institute, University of Warwick, Clifford Bridge Road, Coventry CV2 2DX, UK
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58
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O'Connor MS, Carlson ME, Conboy IM. Differentiation rather than aging of muscle stem cells abolishes their telomerase activity. Biotechnol Prog 2009; 25:1130-7. [PMID: 19455648 DOI: 10.1002/btpr.223] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A general feature of stem cells is the ability to routinely proliferate to build, maintain, and repair organ systems. Accordingly, embryonic and germline, as well as some adult stem cells, produce the telomerase enzyme at various levels of expression. Our results show that, while muscle is a largely postmitotic tissue, the muscle stem cells (satellite cells) that maintain this biological system throughout adult life do indeed display robust telomerase activity. Conversely, primary myoblasts (the immediate progeny of satellite cells) quickly and dramatically downregulate telomerase activity. This work thus suggests that satellite cells, and early transient myoblasts, may be more promising therapeutic candidates for regenerative medicine than traditionally utilized myoblast cultures. Muscle atrophy accompanies human aging, and satellite cells endogenous to aged muscle can be triggered to regenerate old tissue by exogenous molecular cues. Therefore, we also examined whether these aged muscle stem cells would produce tissue that is "young" with respect to telomere maintenance. Interestingly, this work shows that the telomerase activity in muscle stem cells is largely retained into old age wintin inbred "long" telomere mice and in wild-derived short telomere mouse strains, and that age-specific telomere shortening is undetectable in the old differentiated muscle fibers of either strain. Summarily, this work establishes that young and old muscle stem cells, but not necessarily their progeny, myoblasts, are likely to produce tissue with normal telomere maintenance when used in molecular and regenerative medicine approaches for tissue repair.
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Affiliation(s)
- Matthew S O'Connor
- Department of Bioengineering, University of California, Berkeley, CA 94720, USA
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59
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Butts S, Riethman H, Ratcliffe S, Shaunik A, Coutifaris C, Barnhart K. Correlation of telomere length and telomerase activity with occult ovarian insufficiency. J Clin Endocrinol Metab 2009; 94:4835-43. [PMID: 19864453 PMCID: PMC2795650 DOI: 10.1210/jc.2008-2269] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Occult ovarian insufficiency is associated with infertility, impaired response to ovarian stimulation, and reduced live birth rates in women treated with assisted reproductive technologies. Although a decline in ovarian follicle number is expected with age, the proximate causes of occult ovarian insufficiency in young women remain poorly understood. Abnormalities in telomere length and telomerase activity in human granulosa cells may serve as molecular markers for this condition. METHODS A cross-sectional study was performed. Subjects (37 yr old or less) undergoing in vitro fertilization were classified as cases of occult ovarian insufficiency or controls with mechanical infertility (male or tubal factor). Granulosa cells were acquired at the time of oocyte retrieval to quantify telomere length and telomerase activity. RESULTS Fifty-four women were enrolled. Human granulosa cell telomerase activity was demonstrated, and lack of granulosa cell telomerase activity was associated with occult ovarian insufficiency (odds ratio, 11.0; 95% confidence interval, 1.3-495.6; P = 0.02). Telomeres were shorter in women with occult ovarian insufficiency than in controls (relative telomere/single copy gene ratio, 1.88 vs. 3.15; P = 0.039). CONCLUSIONS Aberrant telomere homeostasis is associated with occult ovarian insufficiency in young women. This finding is consistent with the presence of telomeric attenuation that has been shown in multiple age-related conditions.
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Affiliation(s)
- Samantha Butts
- Division of Infertility and Reproductive Endocrinology, University of Pennsylvania Medical School, 3701 Market Street, Suite 800, Philadelphia, Pennsylvania 19104, USA.
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60
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Hashimoto H, Sudo T, Mikami Y, Otani M, Takano M, Tsuda H, Itamochi H, Katabuchi H, Ito M, Nishimura R. Germ cell specific protein VASA is over-expressed in epithelial ovarian cancer and disrupts DNA damage-induced G2 checkpoint. Gynecol Oncol 2008; 111:312-9. [PMID: 18805576 DOI: 10.1016/j.ygyno.2008.08.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2008] [Revised: 08/10/2008] [Accepted: 08/12/2008] [Indexed: 01/31/2023]
Abstract
OBJECTIVE Cancer cells have characteristics, such as high telomerase activity and high levels of migration activity and proliferation, which are very similar to those of germ cell lineages. In this study, we examined the expression of VASA, a germ cell lineage specific marker and evaluated its clinical significance in epithelial ovarian cancer (EOC). METHODS We investigated VASA expression in 75 EOC tissues by immunohistochemistry, correlating results with clinicopathological factors. To clarify the effects of VASA on cellular phenotypes, we compared the protein expression profiles between SKOV-3 cells stably expressing VASA (SKOV-3-VASA) and vector-control cell lines by coupling 2D fingerprinting and identification of proteins by mass spectrometry. RESULTS VASA expression in tumor cells was found in 21 of 75 cases and was positively correlated with high age and serous histology. Significant down-regulation of 14-3-3sigma was observed in SKOV-3-VASA versus control cells. Over-expression of VASA abrogates the G2 checkpoint, induced by DNA damage, by down-regulating the expression of 14-3-3sigma. CONCLUSIONS These results suggest that VASA may either play a direct role in the progression of EOC or serve as a valuable marker of tumorigenesis.
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61
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Alexander B, Coppola G, Perrault SD, Peura TT, Betts DH, King WA. Telomere length status of somatic cell sheep clones and their offspring. Mol Reprod Dev 2008; 74:1525-37. [PMID: 17455196 DOI: 10.1002/mrd.20735] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This study was carried out to determine the telomere length status of sheep clones and their offspring, and to examine telomere dynamics and chromosomal abnormalities in culture propagated donor cells. Skin samples were collected from somatic cell nuclear transfer-derived sheep clones, and three of their progeny generated by natural mating. Samples were collected from control animals (n = 35), spanning in age from 1 month to 36 months of age. Genomic DNA was extracted from cell/tissue samples and their telomere lengths were assessed by terminal restriction fragment (TRF) analysis. Results revealed: that (a) sheep clones derived from cultured somatic cells have shortened telomere lengths compared to age-matched controls; (b) the offspring derived from natural mating between clones had normal telomere lengths compared to their age-matched counterparts; and donor cell cultures beyond 20 population doublings had significantly (P < 0.05) shortened telomeres and exhibited a higher numerical and structural chromosomal abnormalities.
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Affiliation(s)
- Basil Alexander
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
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62
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Abstract
Telomeres are essential for genomic stability and their dysfunction has been implicated in cancer and ageing. The most prominent function of the telomeres is to protect chromosome ends against degradation and fusion, which, in turn, requires maintenance of telomere DNA to a critical length that allows assembly of end-capping structures. During early meiosis, telomeres play the distinctive function of anchoring chromosomes to the inner nuclear membrane. Subsequently, as a consequence of the nuclear membrane polarization, telomeres cluster together into a bouquet configuration, which facilitates pairing and recombination of the homologous chromosomes. Here we review how the two fundamental aspects of telomere maintenance, elongation and protection, contribute to the essential functions performed by telomeres during meiosis.
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63
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Abstract
The traditional view in respect to female reproduction is that the number of oocytes at birth is fixed and continuously declines towards the point when no more oocytes are available after menopause. In this review we briefly discuss the embryonic development of female germ cells and ovarian follicles. The ontogeny of the hypothalamic-pituitary-gonadal axis is then discussed, with a focus on pubertal transition and normal ovulatory menstrual cycles during female adult life. Biochemical markers of menopausal transition are briefly examined. We also examine the effects of age on female fertility, the contribution of chromosomal abnormalities of the oocyte to the observed decline in female fertility with age and the possible biological basis for the occurrence of such abnormalities. Finally, we consider the effects of maternal age on obstetric complications and perinatal outcome. New data that have the potential to revolutionize our understanding of mammalian oogenesis and follicular formation, and of the female reproductive ageing process, are also briefly considered.
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Affiliation(s)
- O Djahanbakhch
- Academic Unit for Women's Health, Barts and The London, Queen Mary's School of Medicine and Dentistry, University of London, UK
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64
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Abstract
Ageing is often defined in the context of telomerase activity and telomere length regulation. Most somatic cells have limited replication ability and undergo senescence eventually. Stem cells are unique as they possess more abundant telomerase activity and are able to maintain telomere lengths for a longer period. Embryonic stem cells are particularly resistant to ageing and can be propagated indefinitely. Remarkably, adult somatic cells can be reprogrammed to an ESC-like state by various means including cell fusion, exposure to ESC cell-free extracts, enforced expression of specific molecules, and somatic cell nuclear transfer. Thus, the rejuvenation of an 'aged' state can be effected by the activation of specific key molecules in the cell. Here, we argue that cellular ageing is a reversible process, and this is determined by the balance of biological molecules which directly or indirectly control telomere length and telomerase activity, either through altering gene expression and/or modulating the epigenetic state of the chromatin.
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Affiliation(s)
- Wai-Leong Tam
- Stem Cell & Developmental Biology, Genome Institute of Singapore, Singapore 138672, Singapore
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65
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Coussens M, Yamazaki Y, Moisyadi S, Suganuma R, Yanagimachi R, Allsopp R. Regulation and effects of modulation of telomerase reverse transcriptase expression in primordial germ cells during development. Biol Reprod 2006; 75:785-91. [PMID: 16899651 DOI: 10.1095/biolreprod.106.052167] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Telomere length maintenance in the germ line from generation to generation is essential for the perpetuation of eukaryotic organisms. This task is performed by a specialized reverse transcriptase called telomerase. While this critical function of telomerase has been well established, the mechanisms that regulate telomerase in the germ line are still poorly understood. We now show, using a Pou5f1-GFP transgenic mouse model, that telomerase suppression in quiescent male primordial germ cells (PGCs) is accompanied by a decrease in expression of murine telomerase reverse transcriptase (TERT). To further assess the role of TERT in quiescent PGCs, we developed a chicken Actb gene promoter/cytomegalovirus enhancer (CAG)-Tert transgenic mouse strain that constitutively expresses murine TERT. Telomerase activity was detected in quiescent PGCs from CAG-Tert transgenic embryos, demonstrating that re-activation of TERT expression is sufficient to restore telomerase activity in these cells and implying that TERT expression is an important mechanism of telomerase regulation in PGCs. Fluorescence-activated cell-sorting (FACS) analysis of PGC frequency and cell cycle status revealed no effect of either overexpression or deficiency of TERT in CAG-Tert transgenic mice or Tert knock-out mice respectively. These results demonstrate that TERT per se does not affect proliferation or development of PGCs, in contrast with recent studies that suggest that TERT has a telomere-independent effect in certain stem cells. It is possible that the direct effect of TERT on cell behavior may be dependent on cell type.
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Affiliation(s)
- Matthew Coussens
- Institute for Biogenesis Research, University of Hawaii, Honolulu, Hawaii 96822, USA
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66
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Abstract
PURPOSE OF REVIEW A unifying theory of reproductive aging, based on telomere shortening, is proposed. RECENT FINDINGS Telomere shortening may mediate both 'hits' involved in reproductive aging, that is late exit from the fetal production line and long interval to ovulation in the adult. SUMMARY As women age egg dysfunction increases, with meiotic nondisjunction, embryonic arrest, apoptosis, and miscarriage. Egg dysfunction results from two 'hits' - reduced formation of chiasmata during fetal oogenesis, and accumulation of reactive oxygen damage during the prolonged interval until ovulation. Late exit from a production line during oogenesis presumably contributes to the first hit. The later insult also involves meiotic spindle abnormalities. Telomeres, repetitive sequences of DNA, cap chromosome ends and dissipate during divisions. Oocytes do not divide, but oogonia do, and telomerase, the enzyme responsible for maintaining telomere length, is inefficient, and remains inactive in oocytes and embryos until blastocyst stage. Reactive oxygen also shortens telomeres, so the prolonged interval between birth and ovulation would further shorten telomeres from chronic exposure to reactive oxygen. In support of this theory, experimental shortening of telomeres in mice produced a phenotype similar to reproductive aging in women, with abnormal chiasmata, spindles, cell cycles, apoptosis, and genomic instability, and telomere length in human eggs correlated with in-vitro fertilization outcome.
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Affiliation(s)
- David L Keefe
- University of South Florida, Department of Obstetrics and Gynecology, Tampa, Florida 33606, USA.
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67
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Baird DM, Britt-Compton B, Rowson J, Amso NN, Gregory L, Kipling D. Telomere instability in the male germline. Hum Mol Genet 2005; 15:45-51. [PMID: 16311252 DOI: 10.1093/hmg/ddi424] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Telomeres play a key role in upholding the integrity of the genome, and telomerase expression in spermatogonial stem cells is responsible for the maintenance of telomere length in the human male germline. We have previously described extensive allelic variation in somatic cell telomere length that is set in the zygote, the ultimate source of which may be the germline. This implies that despite telomerase activity, substantial telomere length variation can be generated and tolerated in the germline; in order to investigate this further, we have examined the nature of telomere length variation in the human male germline. Here, we describe an analysis of both genome-wide telomere length and single molecule analysis of specific chromosome ends in human sperm. We observed individual specific differences in genome-wide telomere length. This variation may result from genetic differences within the components that determine the telomere length setting of each individual. Superimposed on the genome wide telomere length setting was a stochastic component of variation that generates germ-cells containing severely truncated telomeres. If not re-lengthened during early embryogenesis, such telomeres may limit the replicative capacity of cells derived from the zygote and have the potential to create fusagenic chromosomes, unbalanced translocations and terminal micro-deletions. These data may have implications for the genetic determination of ageing, genetic disease and fertility.
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Affiliation(s)
- Duncan M Baird
- Department of Pathology, Cardiff University, Heath Park, Cardiff, UK.
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68
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The Amount of Telomeres and Telomerase Activity on Chicken Embryonic Cells During Developmental Stages. JOURNAL OF ANIMAL SCIENCE AND TECHNOLOGY 2005. [DOI: 10.5187/jast.2005.47.2.187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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69
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Wang CW, Yao DS, Horng SG, Chiu HC, Chen CK, Lee CL, Huang HY, Wang HS, Soong YK, Pao CC. Feasibility of human telomerase reverse transcriptase mRNA expression in individual blastomeres as an indicator of early embryo development. J Assist Reprod Genet 2005; 21:163-8. [PMID: 15279323 PMCID: PMC3455524 DOI: 10.1023/b:jarg.0000031249.37862.3a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
PURPOSE The study was undertaken to test whether human telomerase reverse transcriptase (hTERT) transcripts in an individual blastomere could be used as an indicator for embryo development. METHODS Group A consisted of day 3 normal cleaving embryos at 4- to 8-cell stage, which were surplus and not allocated for uterine transfer. Group B consisted of arrested or fragmented embryos at the same stage, which were considered to be compromised. After blastomere dissociation, RNA purification, reverse transcription, and hTERT PCR amplification, the amplified product was separated by 3% gel electrophoresis. RESULTS Eighty-six (90.5%) of the 95 intact blastomeres in group A and 78 (70.9%) of the 110 blastomeres in group B demonstrated hTERT mRNA expression. The difference was statistically significant (P < 0.05, chi-square). Eight (38.1%) of the 21 embryos in group A and 22 (62.9%) of the 35 embryos in group B had at least one blastomere that did not express hTERT mRNA under this procedure. The difference was not significant (P > 0.05, chi-square). CONCLUSIONS General hTERT mRNA transcripts can be detected in most of the individual blastomeres but cannot be used as an indicator for early embryo development. Further investigations are necessary to elucidate its clinical application.
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Affiliation(s)
- Chia-Woei Wang
- Department of Obstetrics and Gynecology, Chang Gung Memorial Hospital, Lin-Kou Medical Center, 5 Fu-Hsing Street, Kwei-Shan, Tao-Yuan, Taiwan.
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70
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Bekaert S, Derradji H, Baatout S. Telomere biology in mammalian germ cells and during development. Dev Biol 2004; 274:15-30. [PMID: 15355785 DOI: 10.1016/j.ydbio.2004.06.023] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2003] [Revised: 06/18/2004] [Accepted: 06/21/2004] [Indexed: 01/12/2023]
Abstract
The development of an organism is a strictly regulated program in which controlled gene expression guarantees the establishment of a specific phenotype. The chromosome termini or so-called telomeres preserve the integrity of the genome within developing cells. In the germline, during early development, and in highly proliferative organs, human telomeres are balanced between shortening processes with each cell division and elongation by telomerase, but once terminally differentiated or mature the equilibrium is shifted to gradual shortening by repression of the telomerase enzyme. Telomere length is to a large extent genetically determined and the neonatal telomere length equilibrium is, in fact, a matter of evolution. Gradual telomere shortening in normal human somatic cells during consecutive rounds of replication eventually leads to critically short telomeres that induce replicative senescence in vitro and probably in vivo. Hence, a molecular clock is set during development, which determines the replicative potential of cells during extrauterine life. Telomeres might be directly or indirectly implicated in longevity determination in vivo, and information on telomere length setting in utero and beyond should help elucidate presumed causal connections between early growth and aging disorders later in life. Only limited information exists concerning the mechanisms underlying overall telomere length regulation in the germline and during early development, especially in humans. The intent of this review is to focus on recent advances in our understanding of telomere biology in germline cells as well as during development (pre- and postimplantation periods) in an attempt to summarize our knowledge about telomere length determination and its importance for normal development in utero and the occurrence of the aging and abnormal phenotype later on.
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Affiliation(s)
- Sofie Bekaert
- Laboratory for Biochemistry and Molecular Cytology, Department for Molecular Biotechnology, FLTBW-Ghent University, Belgium
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71
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Saikhun J, Sritanaudomchai H, Pavasuthipaisit K, Kitiyanant Y. Telomerase Activity in Swamp Buffalo (Bubalus bubalis) Oocytes and Embryos Derived from In Vitro Fertilization, Somatic Cell Nuclear Transfer and Parthenogenetic Activation. Reprod Domest Anim 2004; 39:162-7. [PMID: 15182292 DOI: 10.1111/j.1439-0531.2004.00495.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The objective of this study was to examine the telomerase activity in swamp buffalo oocytes and pre-implantation stage embryos derived from in vitro fertilization (IVF), somatic cell nuclear transfer (NT) and parthenogenetic activation (PA). Immature and mature oocytes, and embryos at the 2-4 cell, 8-16 cell, morula and blastocyst stages produced by IVF, NT and PA were collected and the telomerase activity was assayed by using a Telomerase PCR ELISA kit. Telomerase activity was detected in all developmental stages evaluated from immature oocytes to blastocyst stage embryos. Telomerase activity was detected in higher amounts in immature as compared with mature oocytes (p < 0.05). Embryos derived from NT showed a profile of telomerase activity similar to that of IVF. In IVF and NT embryos, telomerase activity was low in the 2-4 cell and 8-16 cell stages, but the activity significantly increased (p < 0.05) at the morula stage, reaching its highest level at the blastocyst stage. In PA embryos, low levels of telomerase activity were detected from the 2-4 cell to the morula stage, and the highest level of telomerase activity was found at the blastocyst stage. Telomerase activity in NT blastocysts is higher than that derived from IVF and the activity is highest in PA blastocysts. These results suggest that the successful reprogramming of telomerase activity in buffalo NT embryos follow a pattern similar to that in embryos derived from IVF and PA.
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Affiliation(s)
- J Saikhun
- Department of Anatomy, Faculty of Science, Mahidol University, Bangkok, Thailand
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72
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Schaetzlein S, Lucas-Hahn A, Lemme E, Kues WA, Dorsch M, Manns MP, Niemann H, Rudolph KL. Telomere length is reset during early mammalian embryogenesis. Proc Natl Acad Sci U S A 2004; 101:8034-8. [PMID: 15148368 PMCID: PMC419552 DOI: 10.1073/pnas.0402400101] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The enzyme telomerase is active in germ cells and early embryonic development and is crucial for the maintenance of telomere length. Whereas the different length of telomeres in germ cells and somatic cells is well documented, information on telomere length regulation during embryogenesis is lacking. In this study, we demonstrate a telomere elongation program at the transition from morula to blastocyst in mice and cattle that establishes a specific telomere length set point during embryogenesis. We show that this process restores telomeres in cloned embryos derived from fibroblasts, regardless of the telomere length of donor nuclei, and that telomere elongation at this stage of embryogenesis is telomerase-dependent because it is abrogated in telomerase-deficient mice. These data demonstrate that early mammalian embryos have a telomerase-dependent genetic program that elongates telomeres to a defined length, possibly required to ensure sufficient telomere reserves for species integrity.
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Affiliation(s)
- Sonja Schaetzlein
- Department of Gastroenterology, Hepatology, and Endocrinology, and Institute for Animal Science, Hannover Medical School, 30625 Hannover, Germany
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73
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Xu J, Yang X. Will cloned animals suffer premature aging--the story at the end of clones' chromosomes. Reprod Biol Endocrinol 2003; 1:105. [PMID: 14617371 PMCID: PMC305328 DOI: 10.1186/1477-7827-1-105] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2003] [Accepted: 11/14/2003] [Indexed: 11/10/2022] Open
Affiliation(s)
- Jie Xu
- Evergen Biotechnologies, Inc. 1392 Storrs Road, Unit 4213, University of Connecticut Incubator Program, Storrs, CT 06269, USA
| | - Xiangzhong Yang
- Department of Animal Sciences and the Center for Regenerative Biology, 1392 Storrs Road, University of Connecticut, Storrs, CT 06269, USA
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74
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Abstract
Many regulatory systems operate in the early mammalian embryo. This brief overview surveys several systems and their integration including polarities and axes, left-right differentiation, timers in cells, tissues and in gene expression, and imprinting. Polarities are essential from the very earliest stages of oocyte formation, and maintain their significance until blastocyst stages and beyond. They determine cleavage axes and the distribution of maternal proteins in the oocyte, distinct distributions being identified at the animal pole especially. Left-right axes are no doubt expressed from the earliest embryonic stages, and perhaps even in determining slight differences in the axes of cleavage and of maternal protein distribution. Timers, equally fundamental, have been demonstrated to control many functions in oocytes and embryos. Many fundamental processes in early mammalian oocytes and embryos are closely timed. They are classified into circadian rhythms, hourglass timers, clocks regulating major aspects of development including transcription, longevity via telomere clocks and long-range systems. Imprinting and methylation, increasingly important in establishing stable phenotypes in early embryos, might develop abnormally under some circumstances including intracytoplasmic sperm injection and cloning. A general summary briefly describes some other aspects of regulation, especially chromosomal anomalies in human embryos.
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Affiliation(s)
- R G Edwards
- Reproductive BioMedicine Online, Duck End Farm, Dry Drayton, Cambridge CB3 8DB, UK.
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75
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Liu L, Blasco M, Trimarchi J, Keefe D. An essential role for functional telomeres in mouse germ cells during fertilization and early development. Dev Biol 2002; 249:74-84. [PMID: 12217319 DOI: 10.1006/dbio.2002.0735] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Late generations of telomerase-null (TR(-/-)) mice exhibit progressive defects in highly proliferative tissues and organs and decreased fertility, ultimately leading to sterility. To determine effects of telomerase deficiency on germ cells, we investigated the cleavage and preimplantation development of embryos derived from both in vivo and in vitro fertilization of TR(-/-) or wild-type (TR(+/+)) sperm with either TR(-/-) or TR(+/+) oocytes. Consistently, fertilization of TR(-/-) oocytes with either TR(+/+) or TR(-/-) sperm, and TR(-/-) sperm with TR(+/+) oocytes, resulted in aberrant cleavage and development, in contrast to the normal cleavage and development of TR(+/+) oocytes fertilized by TR(+/+) sperm. Many (>50%) of the fertilized TR(-/-) eggs developed only one pronucleus, coincident with increased incidence of cytofragmentation, in contrast to the normal formation of two pronuclei and equal cleavage of wild-type embryos. These results suggest that both TR(-/-) sperm and oocytes contribute to defective fertilization and cleavage. We further found that a subset (7-9%) of telomeres was undetectable at the ends of some metaphase I chromosomes from TR(-/-) spermatocytes and oocytes, indicating that meiotic germ cells lacking telomerase ultimately resulted in telomere shortening and loss. Dysfunction of meiotic telomeres may contribute to aberrant fertilization of gametes and lead to abnormal cleavage of embryos, implying an important role of functional telomeres for germ cells undergoing fertilization and early cleavage development.
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Affiliation(s)
- Lin Liu
- Department of Immunology and Oncology, National Centre of Biotechnology, Madrid, E-28049, Spain
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