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Zhang N, Baker EC, Welsh TH, Riley DG. Telomere Dynamics in Livestock. BIOLOGY 2023; 12:1389. [PMID: 37997988 PMCID: PMC10669808 DOI: 10.3390/biology12111389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 10/26/2023] [Accepted: 10/27/2023] [Indexed: 11/25/2023]
Abstract
Telomeres are repeated sequences of nucleotides at the end of chromosomes. They deteriorate across mitotic divisions of a cell. In Homo sapiens this process of lifetime reduction has been shown to correspond with aspects of organismal aging and exposure to stress or other insults. The early impetus to characterize telomere dynamics in livestock related to the concern that aged donor DNA would result in earlier cell senescence and overall aging in cloned animals. Telomere length investigations in dairy cows included breed effects, estimates of additive genetic control (heritability 0.12 to 0.46), and effects of external stressors on telomere degradation across animal life. Evaluation of telomeres with respect to aging has also been conducted in pigs and horses, and there are fewer reports of telomere biology in beef cattle, sheep, and goats. There were minimal associations of telomere length with animal productivity measures. Most, but not all, work in livestock has documented an inverse relationship between peripheral blood cell telomere length and age; that is, a longer telomere length was associated with younger age. Because livestock longevity affects productivity and profitability, the role of tissue-specific telomere attrition in aging may present alternative improvement strategies for genetic improvement while also providing translational biomedical knowledge.
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Affiliation(s)
- Nan Zhang
- Department of Animal Science, Texas A&M University, College Station, TX 77843, USA; (N.Z.); (T.H.W.J.)
| | - Emilie C. Baker
- Department of Agricultural Sciences, West Texas A&M University, Canyon, TX 79016, USA;
| | - Thomas H. Welsh
- Department of Animal Science, Texas A&M University, College Station, TX 77843, USA; (N.Z.); (T.H.W.J.)
- Texas A&M AgriLife Research, College Station, TX 77843, USA
| | - David G. Riley
- Department of Animal Science, Texas A&M University, College Station, TX 77843, USA; (N.Z.); (T.H.W.J.)
- Texas A&M AgriLife Research, College Station, TX 77843, USA
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Cherdyntseva V, Gagos S. Chromosome extremities under the microscopy lens: molecular cytogenetics in telomere research. Curr Opin Genet Dev 2020; 60:69-76. [PMID: 32193147 DOI: 10.1016/j.gde.2020.02.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 02/03/2020] [Accepted: 02/06/2020] [Indexed: 02/07/2023]
Abstract
At the crossroads of DNA damage repair and genomic instability, telomere research significantly expands our knowledge on fundamental mechanisms involved in cancer initiation and progression, pledging novel tools for targeted and universal onco-therapies. Molecular cytogenetics through the application of a battery of fluorescent hybridization technologies plays an important role toward understanding telomere homeostasis. Herein, we review distinct molecular cytogenetic phenotypes associated with telomere repair, functionality, and elongation. We discuss the underlying mechanisms responsible for their formation or repair, focusing on Break-induced-Replication (BIR)-mediated conservative telomeric neo-synthesis, recently shown to drive the enigmatic Alternative Lengthening of Telomeres in neoplasia.
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Affiliation(s)
- Veronica Cherdyntseva
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, 11527, Greece
| | - Sarantis Gagos
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, 11527, Greece.
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Bolzán AD. Interstitial telomeric sequences in vertebrate chromosomes: Origin, function, instability and evolution. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2017; 773:51-65. [PMID: 28927537 DOI: 10.1016/j.mrrev.2017.04.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 03/13/2017] [Accepted: 04/17/2017] [Indexed: 12/21/2022]
Abstract
By definition, telomeric sequences are located at the very ends or terminal regions of chromosomes. However, several vertebrate species show blocks of (TTAGGG)n repeats present in non-terminal regions of chromosomes, the so-called interstitial telomeric sequences (ITSs), interstitial telomeric repeats or interstitial telomeric bands, which include those intrachromosomal telomeric-like repeats located near (pericentromeric ITSs) or within the centromere (centromeric ITSs) and those telomeric repeats located between the centromere and the telomere (i.e., truly interstitial telomeric sequences) of eukaryotic chromosomes. According with their sequence organization, localization and flanking sequences, ITSs can be classified into four types: 1) short ITSs, 2) subtelomeric ITSs, 3) fusion ITSs, and 4) heterochromatic ITSs. The first three types have been described mainly in the human genome, whereas heterochromatic ITSs have been found in several vertebrate species but not in humans. Several lines of evidence suggest that ITSs play a significant role in genome instability and evolution. This review aims to summarize our current knowledge about the origin, function, instability and evolution of these telomeric-like repeats in vertebrate chromosomes.
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Affiliation(s)
- Alejandro D Bolzán
- Laboratorio de Citogenética y Mutagénesis, Instituto Multidisciplinario de Biología Celular (IMBICE, CICPBA-UNLP-CONICET La Plata), C.C. 403, 1900 La Plata, Argentina; Facultad de Ciencias Naturales y Museo, UNLP, Calle 60 y 122, 1900 La Plata, Argentina.
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Kong Q, Ji G, Xie B, Li J, Mao J, Wang J, Liu S, Liu L, Liu Z. Telomere elongation facilitated by trichostatin a in cloned embryos and pigs by somatic cell nuclear transfer. Stem Cell Rev Rep 2014; 10:399-407. [PMID: 24510582 DOI: 10.1007/s12015-014-9499-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Telomere attrition and genomic instability are associated with organism aging. Concerns still exist regarding telomere length resetting in cloned embryos and ntES cells, and possibilities of premature aging of cloned animals achieved by somatic cell nuclear transfer (SCNT). Trichostatin A (TSA), a histone deacetylase inhibitor, effectively improves the developmental competence of cloned embryos and animals, and recently contributes to successful generation of human ntES cells by SCNT. To test the function of TSA on resetting telomere length, we analyzed telomeres in cloned blastocysts and pigs following treatment of SCNT embryos with TSA. Here, we show that telomeres of cloned pigs generated by standard SCNT methods are not effectively restored, compared with those of donor cells, however TSA significantly increases telomere lengths in cloned pigs. Telomeres elongate in cloned porcine embryos during early cleavage from one-cell to four-cell stages. Notably, TSA facilitates telomere lengthening of cloned embryos mainly at morula-blastocyst stages. Knockdown of pTert by shRNA in donor cells reduces telomerase activity in cloned blastocysts but does not abrogate telomere elongation in the TSA-treated embryos (p > 0.05). However, genes associated with recombination or telomerase-independent mechanism of alternative lengthening of telomeres (ALT) Rad50 and BLM show increased expression in TSA-treated embryos. These data suggest that TSA may promote telomere elongation of cloned porcine embryos by ALT. Together, TSA can elongate telomeres in cloned embryos and piglets, and this could be one of the mechanisms underlying improved development of cloned embryos and animals treated with TSA.
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Affiliation(s)
- Qingran Kong
- Laboratory of Embryo Biotechnology, College of Life Science, Northeast Agricultural University, Harbin, China,
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Alternative lengthening of telomeres: recurrent cytogenetic aberrations and chromosome stability under extreme telomere dysfunction. Neoplasia 2014; 15:1301-13. [PMID: 24339742 DOI: 10.1593/neo.131574] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 10/17/2013] [Accepted: 10/21/2013] [Indexed: 12/23/2022] Open
Abstract
Human tumors using the alternative lengthening of telomeres (ALT) exert high rates of telomere dysfunction. Numerical chromosomal aberrations are very frequent, and structural rearrangements are widely scattered among the genome. This challenging context allows the study of telomere dysfunction-driven chromosomal instability in neoplasia (CIN) in a massive scale. We used molecular cytogenetics to achieve detailed karyotyping in 10 human ALT neoplastic cell lines. We identified 518 clonal recombinant chromosomes affected by 649 structural rearrangements. While all human chromosomes were involved in random or clonal, terminal, or pericentromeric rearrangements and were capable to undergo telomere healing at broken ends, a differential recombinatorial propensity of specific genomic regions was noted. We show that ALT cells undergo epigenetic modifications rendering polycentric chromosomes functionally monocentric, and because of increased terminal recombinogenicity, they generate clonal recombinant chromosomes with interstitial telomeric repeats. Losses of chromosomes 13, X, and 22, gains of 2, 3, 5, and 20, and translocation/deletion events involving several common chromosomal fragile sites (CFSs) were recurrent. Long-term reconstitution of telomerase activity in ALT cells reduced significantly the rates of random ongoing telomeric and pericentromeric CIN. However, the contribution of CFS in overall CIN remained unaffected, suggesting that in ALT cells whole-genome replication stress is not suppressed by telomerase activation. Our results provide novel insights into ALT-driven CIN, unveiling in parallel specific genomic sites that may harbor genes critical for ALT cancerous cell growth.
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Gao Y, Guo Y, Duan A, Cheng D, Zhang S, Wang H. Optimization of culture conditions for maintaining porcine induced pluripotent stem cells. DNA Cell Biol 2013; 33:1-11. [PMID: 24256201 DOI: 10.1089/dna.2013.2095] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Ground state porcine induced pluripotent stem cells (piPSCs), which retain the potential to generate chimeric animal and germline transmission, are difficult to produce. This study investigated morphological and biological progression at the early stage of porcine somatic cell reprogramming, and explored suitable conditions to increase the induction efficiency of piPSCs. A cocktail of defined transcription factors was used to generate piPSCs. The amphotropic retrovirus, which carried human OCT4 (O), SOX2 (S), KLF4 (K), C-MYC (M), TERT (T), and GFP, were used to infect porcine embryonic fibroblasts (PEFs). The number of clones derived from OSKM (4F) and OSKMT (4F+T) was significantly higher than that from SKM (3F) and SKMT (3F+T), suggesting that OCT4 played a critical role in regulating porcine cell reprogramming. The number of alkaline phosphatase-positive clones from a medium with leukemia inhibitory factor (LIF) and basic fibroblast growth factor (bFGF) (M1 medium) was significantly higher than that with insulin and 2i PD0325901/CHIR99021 (M2 medium), indicating that insulin and 2i could not effectively maintain piPSC propagation. In the M1 medium, piPSC lines could not maintain the typical self-renewal morphology on gelatin-coated and Matrigel-coated plates. Without the mouse embryonic fibroblast (MEF) feeder, piPSCs started to simultaneously differentiate. Based on the potential for self-renewal and activation of pluripotent markers, we found that the culture condition of 4F+T plus LIF and bFGF plus MEF feeder promoted PEF reprogramming more efficiently than the other conditions tested here. Two piPSC lines (IB-1 and IB-2) were derived and maintained for up to 20 passages in vitro.
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Affiliation(s)
- Yi Gao
- Department of Animal Biotechnology, College of Veterinary Medicine , Northwest A&F University, Yangling, Shaanxi, China
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Telomere reprogramming and maintenance in porcine iPS cells. PLoS One 2013; 8:e74202. [PMID: 24098638 PMCID: PMC3787036 DOI: 10.1371/journal.pone.0074202] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 07/29/2013] [Indexed: 01/12/2023] Open
Abstract
Telomere reprogramming and silencing of exogenous genes have been demonstrated in mouse and human induced pluripotent stem cells (iPS cells). Pigs have the potential to provide xenotransplant for humans, and to model and test human diseases. We investigated the telomere length and maintenance in porcine iPS cells generated and cultured under various conditions. Telomere lengths vary among different porcine iPS cell lines, some with telomere elongation and maintenance, and others telomere shortening. Porcine iPS cells with sufficient telomere length maintenance show the ability to differentiate in vivo by teratoma formation test. IPS cells with short or dysfunctional telomeres exhibit reduced ability to form teratomas. Moreover, insufficient telomerase and incomplete telomere reprogramming and/or maintenance link to sustained activation of exogenous genes in porcine iPS cells. In contrast, porcine iPS cells with reduced expression of exogenous genes or partial exogene silencing exhibit insufficient activation of endogenous pluripotent genes and telomerase genes, accompanied by telomere shortening with increasing passages. Moreover, telomere doublets, telomere sister chromatid exchanges and t-circles that presumably are involved in telomere lengthening by recombination also are found in porcine iPS cells. These data suggest that both telomerase-dependent and telomerase-independent mechanisms are involved in telomere reprogramming during induction and passages of porcine iPS cells, but these are insufficient, resulting in increased telomere damage and shortening, and chromosomal instability. Active exogenes might compensate for insufficient activation of endogenous genes and incomplete telomere reprogramming and maintenance of porcine iPS cells. Further understanding of telomere reprogramming and maintenance may help improve the quality of porcine iPS cells.
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