Telomeres in cancer and ageing

Targeting shelterin proteins for cancer therapy

As a global health challenge, cancer prompts continuous exploration for innovative therapies that are also based on new targets. One promising avenue is targeting the shelterin protein complex, a safeguard for telomeres crucial in preventing DNA damage. The role of shelterin in modulating ataxia-telangiectasia mutated (ATM) and ataxia-telangiectasia and Rad3-related (ATR) kinases, key players in the DNA damage response (DDR), establishes its significance in cancer cells. Disrupting these defence mechanisms of shelterins, especially in cancer cells, renders telomeres vulnerable, potentially leading to genomic instability and hindering cancer cell survival. In this review, we outline recent approaches exploring shelterins as potential anticancer targets, highlighting the prospect of developing selective molecules to exploit telomere vulnerabilities toward new innovative cancer treatments.

Exploring role of natural compounds in molecular alterations associated with brain ageing: A perspective towards nutrition for ageing brain

Aging refers to complete deterioration of physiological integrity and function. By midcentury, adults over 60 years of age and children under 15 years will begin to outnumber people in working age. This shift will bring multiple global challenges for economy, health, and society. Eventually, aging is a natural process playing a vital function in growth and development during pediatric stage, maturation during adult stage, and functional depletion. Tissues experience negative consequences with enhanced genomic instability, deregulated nutrient sensing, mitochondrial dysfunction, and decline in performance on cognitive tasks. As brain ages, its volume decreases, neurons & glia get inflamed, vasculature becomes less developed, blood pressure increases with a risk of stroke, ischemia, and cognitive deficits. Diminished cellular functions leads to progressive reduction in functional and emotional capacity with higher possibility of disease and finally death. This review overviews cellular as well as molecular aspects of aging, biological pathway related to accelerated brain aging, and strategies minimizing cognitive aging. Age-related changes include altered bioenergetics, decreased neuroplasticity and flexibility, aberrant neural activity, deregulated Ca2+ homeostasis in neurons, buildup of reactive oxygen species, and neuro-inflammation. Unprecedented progress has been achieved in recent studies, particularly in terms of how herbal or natural substances affect genetic pathways and biological functions that have been preserved through evolution. Herein, the present work provides an overview of ageing and age-related disorders and explore the molecular mechanisms that underlie therapeutic effects of herbal and natural chemicals on neuropathological signs of brain aging.

Chromosome ends and the theory of marginotomy: implications for reproduction

Telomeres are the protective structures located at the ends of linear chromosomes. They were first described in the 1930s, but their biology remained unexplored until the early 70s, when Alexey M. Olovnikov, a theoretical biologist, suggested that telomeres cannot be fully copied during DNA replication. He proposed a theory that linked this phenomenon with the limit of cell proliferation capacity and the "duration of life" (theory of marginotomy), and suggested a potential of telomere lenghthening for the prevention of aging (anti-marginotomy). The impact of proliferative telomere shortening on life expectancy was later confirmed. In humans, telomere shortening is counteracted by telomerase, an enzyme that is undetectable in most adult somatic cells, but present in cancer cells and adult and embryonic stem and germ cells. Although telomere length dynamics are different in male and female gametes during gametogenesis, telomere lengths are reset at the blastocyst stage, setting the initial length of the species. The role of the telomere pathway in reproduction has been explored for years, mainly because of increased infertility resulting from delayed childbearing. Short telomere length in ovarian somatic cells is associated to decreased fertility and higher aneuploidy rates in embryos. Consequently, there is a growing interest in telomere lengthening strategies, aimed at improving fertility. It has also been observed that lifestyle factors can affect telomere length and improve fertility outcomes. In this review, we discuss the implications of telomere theory in fertility, especially in oocytes, spermatozoa, and embryos, as well as therapies to enhance reproductive success.

Genetically determined telomere length and its association with chronic obstructive pulmonary disease and interstitial lung disease in biobank Japan: A Mendelian randomization study

Importance

Chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD) have been linked to shorter telomere length (TL). While understanding this association has critical clinical implications for respiratory diseases, previous studies exploring these associations were conducted in European populations. The present study aims to investigate this relationship in an Asian population.

Objective

To examine the causal relationship between leukocyte TL and COPD and ILD in an Asian population.

Design

Setting, and Participants: We used a genome-wide association study summary statistics-based two-sample Mendelian randomization (MR) design to investigate the association between leukocyte TL, genetically predicted by nine single-nucleotide polymorphisms and the risk of COPD and ILD. Participants were Japanese individuals enrolled in the Biobank Japan Project, including 3315 COPD patients and 806 ILD patients.

Exposure

Leukocyte TL was genetically predicted by nine single-nucleotide polymorphisms.

Results

The inverse-variance weighted estimates showed a significant inverse association between leukocyte TL and COPD (odds ratio [OR] = 0.78; 95 % confidence interval [CI]: 0.64, 0.95; P = 0.01) and ILD (OR = 0.29; 95 % CI: 0.14, 0.61; P = 0.001), respectively. All sensitivity analyses yielded consistent results. The MR-Egger regression intercept test showed no evidence of horizontal pleiotropy (Pintercept: COPD, 0.56; ILD: 0.70).

Conclusion

and Relevance: Our findings suggest that leukocyte telomere shortening may causally increase the risk of COPD and ILD. These results highlight the potential importance of TL for these respiratory diseases.

Premature aging and reduced cancer incidence associated with near-complete body-wide Myc inactivation

MYC proto-oncogene dysregulation alters metabolism, translation, and other functions in ways that support tumor induction and maintenance. Although Myc+/- mice are healthier and longer-lived than control mice, the long-term ramifications of more complete Myc loss remain unknown. We now describe the chronic consequences of body-wide Myc inactivation initiated postnatally. "MycKO" mice acquire numerous features of premature aging, including altered body composition and habitus, metabolic dysfunction, hepatic steatosis, and dysregulation of gene sets involved in functions that normally deteriorate with aging. Yet, MycKO mice have extended lifespans that correlate with a 3- to 4-fold lower lifetime cancer incidence. Aging tissues from normal mice and humans also downregulate Myc and gradually alter many of the same Myc target gene sets seen in MycKO mice. Normal aging and its associated cancer predisposition are thus highly linked via Myc.

Impaired telomere pathway and fertility in Senescence-Accelerated Mice Prone 8 females with reproductive senescence

Ovarian aging is the main cause of infertility and telomere attrition is common to both aging and fertility disorders. Senescence-Accelerated Mouse Prone 8 (SAMP8) model has shortened lifespan and premature infertility, reflecting signs of reproductive senescence described in middle-aged women. Thus, our objective was to study SAMP8 female fertility and the telomere pathway at the point of reproductive senescence. The lifespan of SAMP8 and control mice was monitored. Telomere length (TL) was measured by in situ hybridization in blood and ovary. Telomerase activity (TA) was analyzed by telomere-repeat amplification protocol, and telomerase expression, by real-time quantitative PCR in ovaries from 7-month-old SAMP8 and controls. Ovarian follicles at different stages of maturation were evaluated by immunohistochemistry. Reproductive outcomes were analyzed after ovarian stimulation. Unpaired t-test or Mann-Whitney test were used to calculate p-values, depending on the variable distribution. Long-rank test was used to compare survival curves and Fisher's exact test was used in contingency tables. Median lifespan of SAMP8 females was reduced compared to SAMP8 males (p = 0.0138) and control females (p < 0.0001). In blood, 7-month-old SAMP8 females presented lower mean TL compared to age-matched controls (p = 0.041). Accordingly, the accumulation of short telomeres was higher in 7-month-old SAMP8 females (p = 0.0202). Ovarian TA was lower in 7-month-old SAMP8 females compared to controls. Similarly, telomerase expression was lower in the ovaries of 7-month-old SAMP8 females (p = 0.04). Globally, mean TL in ovaries and granulosa cells (GCs) were similar. However, the percentage of long telomeres in ovaries (p = 0.004) and GCs (p = 0.004) from 7-month-old SAMP8 females was lower compared to controls. In early-antral and antral follicles, mean TL of SAMP8 GCs was lower than in age-matched controls (p = 0.0156 for early-antral and p = 0.0037 for antral follicles). Middle-aged SAMP8 showed similar numbers of follicles than controls, although recovered oocytes after ovarian stimulation were lower (p = 0.0068). Fertilization rate in oocytes from SAMP8 was not impaired, but SAMP8 mice produced significantly more morphologically abnormal embryos than controls (27.03% in SAMP8 vs. 1.22% in controls; p < 0.001). Our findings suggest telomere dysfunction in SAMP8 females, at the time of reproductive senescence.

Telomeres and oocyte maturation rate are not reduced by COVID-19 except in severe cases

In brief

COVID-19 does not affect the telomeres or fertility outcomes in mild cases. However, in women with severe symptoms, telomeres of granulosa cells are shorter, and the oocyte maturation rate is decreased.

Abstract

The coronavirus SARS-CoV-2 causes COVID-19 disease and affects primarily the lungs and also other organs, causing accelerated cell aging. One of the main pathways involved in aging is telomere attrition, which ultimately leads to defective tissue regeneration and organ dysfunction. Indeed, short telomeres in aged people aggravate the COVID-19 symptoms, and COVID-19 survivors showed shorter telomeres in blood cells. The SARS-CoV-2 has been detected in testis, but the ovaries, which express the viral entry factors, have not been fully explored. Our objective was to analyze telomeres and reproductive outcomes in women who had COVID-19 and controls. In this prospective cohort study, granulosa cells (GCs) and blood were collected from 65 women. Telomere length (TL) was measured by high-throughput in situ hybridization. Mean TL of GCs and peripheral blood mononuclear cells (PBMCs) was alike in control and mild cases. However, mean TL of GCs was lower in severe cases compared to controls (P = 0.017). Control and COVID groups had similar ovarian reserve and number of total oocytes after puncture. However, the oocyte maturation rate was lower in severe cases (P = 0.018). Interestingly, a positive correlation between the oocyte maturation rate and TL of GCs was found in the control group (P = 0.024). Our findings point to a potential impact of the coronavirus infection on telomeres and reproductive outcomes in severe cases. This might be considered upon possible new SARS-CoV threats, to favor treatments that enhance oocyte maturation in women severely affected by coronavirus undergoing ART.

Association between telomere length in human umbilical cord tissues and polychlorinated biphenyls in maternal and cord serum

Environmental exposure to persistent organic pollutants during pregnancy has potential adverse health effects on the fetus. One of the environmental pollutants is polychlorinated biphenyl (PCB). Earlier, we reported the presence of PCBs in fetal tissues such as the umbilical cord. Telomere length (TL) is a biomarker of aging because it shortens with each cell division. According to the Developmental Origins of Health and Disease hypothesis, fetal exposure to environmental pollutants during pregnancy affects the occurrence of non-communicable diseases in later life. In the current study, we investigated the association between cord tissue TL and serum levels of PCBs. The subjects were 114 mother-child pairs participating in a birth cohort study, the Chiba Study of Mother and Child Health (C-MACH). Maternal serum was collected during pregnancy, and cord serum and tissue were obtained at birth. TL was assessed by qPCR using genomic DNA extracted from the cord tissue. Maternal and cord serum PCB congener levels were assessed using gas chromatography and negative ion chemical ionization qMS. In male fetuses, serum levels of PCB74 in the cord blood were significantly associated with TL following covariate adjustment, but no significant association was found in female fetuses. These data suggest that the TL of the umbilical cord is affected by fetal exposure to PCBs.

Cellular senescence, rejuvenation and potential immortality

Ageing, death, and potential immortality lie at the heart of biology, but two seemingly incompatible paradigms coexist in different research communities and have done since the nineteenth century. The universal senescence paradigm sees senescence as inevitable in all cells. Damage accumulates. The potential immortality paradigm sees some cells as potentially immortal, especially unicellular organisms, germ cells and cancerous cells. Recent research with animal cells, yeasts and bacteria show that damaged cell constituents do in fact build up, but can be diluted by growth and cell division, especially by asymmetric cell division. By contrast, mammalian embryonic stem cells and many cancerous and 'immortalized' cell lines divide symmetrically, and yet replicate indefinitely. How do they acquire their potential immortality? I suggest they are rejuvenated by excreting damaged cell constituents in extracellular vesicles. If so, our understanding of cellular senescence, rejuvenation and potential immortality could be brought together in a new synthesis, which I call the cellular rejuvenation hypothesis: damaged cell constituents build up in all cells, but cells can be rejuvenated either by growth and cell division or, in 'immortal' cell lines, by excreting damaged cell constituents. In electronic supplementary material, appendix, I outline nine ways in which this hypothesis could be tested.

Insights into POT1 structural dynamics revealed by cryo-EM

Telomeres are protein-DNA complexes that protect the ends of linear eukaryotic chromosomes. Mammalian telomeric DNA consists of 5′-(TTAGGG)n-3′ double-stranded repeats, followed by up to several hundred bases of a 3′ single-stranded G-rich overhang. The G-rich overhang is bound by the shelterin component POT1 which interacts with TPP1, the component involved in telomerase recruitment. A previously published crystal structure of the POT1 N-terminal half bound to the high affinity telomeric ligand 5′-TTAGGGTTAG-3′ showed that the first six nucleotides, TTAGGG, are bound by the OB1 fold, while the adjacent OB2 binds the last four, TTAG. Here, we report two cryo-EM structures of full-length POT1 bound by the POT1-binding domain of TPP1. The structures differ in the relative orientation of the POT1 OB1 and OB2, suggesting that these two DNA-binding OB folds take up alternative conformations. Supporting DNA binding studies using telomeric ligands in which the OB1 and OB2 binding sites were spaced apart, show that POT1 binds with similar affinities to spaced or contiguous binding sites, suggesting plasticity in DNA binding and a role for the alternative conformations observed. A likely explanation is that the structural flexibility of POT1 enhances binding to the tandemly arranged telomeric repeats and hence increases telomere protection.

Ageing, Age-Related Cardiovascular Risk and the Beneficial Role of Natural Components Intake

Ageing, in a natural way, leads to the gradual worsening of the functional capacity of all systems and, eventually, to death. This process is strongly associated with higher metabolic and oxidative stress, low-grade inflammation, accumulation of DNA mutations and increased levels of related damage. Detrimental changes that accumulate in body cells and tissues with time raise the vulnerability to environmental challenges and enhance the risk of major chronic diseases and mortality. There are several theses concerning the mechanisms of ageing: genetic, free radical telomerase, mitochondrial decline, metabolic damage, cellular senescence, neuroendocrine theory, Hay-flick limit and membrane theories, cellular death as well as the accumulation of toxic and non-toxic garbage. Moreover, ageing is associated with structural changes within the myocardium, cardiac conduction system, the endocardium as well as the vasculature. With time, the cardiac structures lose elasticity, and fibrotic changes occur in the heart valves. Ageing is also associated with a higher risk of atherosclerosis. The results of studies suggest that some natural compounds may slow down this process and protect against age-related diseases. Animal studies imply that some of them may prolong the lifespan; however, this trend is not so obvious in humans.

Short-term elevations in glucocorticoids do not alter telomere lengths: A systematic review and meta-analysis of non-primate vertebrate studies

Background

The neuroendocrine stress response allows vertebrates to cope with stressors via the activation of the Hypothalamic-Pituitary-Adrenal (HPA) axis, which ultimately results in the secretion of glucocorticoids (GCs). Glucocorticoids have pleiotropic effects on behavior and physiology, and might influence telomere length dynamics. During a stress event, GCs mobilize energy towards survival mechanisms rather than to telomere maintenance. Additionally, reactive oxygen species produced in response to increased GC levels can damage telomeres, also leading to telomere shortening. In our systematic review and meta-analysis, we tested whether GC levels impact telomere length and if this relationship differs among time frame, life history stage, or stressor type. We hypothesized that elevated GC levels are linked to a decrease in telomere length.

Methods

We conducted a literature search for studies investigating the relationship between telomere length and GCs in non-human vertebrates using four search engines: Web of Science, Google Scholar, Pubmed and Scopus, last searched on September 27th, 2020. This review identified 31 studies examining the relationship between GCs and telomere length. We pooled the data using Fisher’s Z for 15 of these studies. All quantitative studies underwent a risk of bias assessment. This systematic review study was registered in the Open Science Framework Registry (https://osf.io/rqve6).

Results

The pooled effect size from fifteen studies and 1066 study organisms shows no relationship between GCs and telomere length (Fisher’s Z = 0.1042, 95% CI = 0.0235; 0.1836). Our meta-analysis synthesizes results from 15 different taxa from the mammalian, avian, amphibian groups. While these results support some previous findings, other studies have found a direct relationship between GCs and telomere dynamics, suggesting underlying mechanisms or concepts that were not taken into account in our analysis. The risk of bias assessment revealed an overall low risk of bias with occasional instances of bias from missing outcome data or bias in the reported result.

Conclusion

We highlight the need for more targeted experiments to understand how conditions, such as experimental timeframes, stressor(s), and stressor magnitudes can drive a relationship between the neuroendocrine stress response and telomere length.

Telomeric zinc-finger associated protein (TZAP) in cancer biology: friend or foe?

The new identified protein telomeric zinc-finger associated protein (TZAP) is a negative regulator of telomere length. Since telomere length and telomere maintenance mechanisms are essential to cancer progression, TZAP is considered a new player in cancer biology. Here we aimed to analyze TZAP using the Cancer Genome Atlas data in a Pan-Cancer approach. We gathering data from TCGA Pan-Cancer studies utilizing cBioPortal, GEPIA and UALCAN. In total we analyzed 33 types of cancer (n=9664) and their respective controls (n=711). TZAP is transcribed in all cancers but less than 5% of all tumors show any somatic changes. TZAP was downregulated in kidney chromophobe carcinoma, and upregulated in esophageal cancer, head and neck squamous cell carcinomas, kidney renal clear cell carcinoma and in liver hepatocellular carcinoma. Globally, TZAP expression is related to favorable prognosis, associated to better overall and disease-free survival. Looking to specific tumors, TZAP expression has a dual behavior. Its downregulation is associated with poor prognosis in cervical squamous cell carcinoma, in kidney renal clear cell carcinoma, kidney papillary cell carcinoma, lung adenocarcinoma and pancreas adenocarcinoma. On the contrary, in adrenocortical carcinoma, colon and rectal cancer, brain lower grade glioma and prostate adenocarcinoma the upregulation of TZAP is related with poor prognosis. TZAP expression has a positive correlation with TRF1 and TRF2 in normal tissue but not in cancer. Our analyses indicate that TZAP has an important role in oncology and may be considered as a potential biomarker.

Constitutional variants in POT1, TERF2IP, and ACD genes in patients with melanoma in the Polish population

Evaluation of the prevalence of POT1, ACD, and TERF2IP mutations among Polish melanoma patients. A cohort of 60 patients from melanoma-prone families, 1500 unselected cases and 1500 controls were genotyped. Methodology included Sanger sequencing, in-silico software predilection, and TaqMan assays. We identified three nonsynonymous variants: POT1 c.903 G>T; TERF2IP c.970 A>G; and ACD c.1544 T>C and a splice site variant ACD c.645 G>A. The c.903 G>T was predicted to be pathogenic according to PolyPhen-2, benign according to Mutation Taster, PROVEAN, AGVGD, and SIFT. The c.645 G>A was defined as disease caused by Mutation Taster and Human Splicing Finder and as variant of unknown significance by ClinVar. The other detected variants were described as benign. The c.903 G>T variant was present in two unselected cases and one control [P = 0.57, odds ratio (OR) = 2.00]; the c.645 G>A variant was not detected among the unselected cases and the controls; the c.970 A>G variant was present in 110 cases and 133 controls (P = 0.14, OR = 0.81); the c.1544 T>C variant was present in 687 cases and 642 controls (P = 0.11, OR = 1.07). We found no loss of heterozygosity of the c.903 G>T, c.970 A>G, and c.645 G>A variants. C.645 G>A variant had no effect on splicing or expression. The changes in POT1 c.903 G>T and ACD c.645 G>A can be classified as rare variants of unknown significance, the other variants appear to be polymorphisms. Germline mutations in POT1, ACD, and TERF2IP are infrequent among Polish melanoma patients.

Reproductive aging and telomeres: Are women and men equally affected?

Successful reproduction is very important for individuals and for society. Currently, the human health span and lifespan are the object of intense and productive investigation with great achievements, compared to the last century. However, reproduction span does not progress concomitantly with lifespan. Reproductive organs age, decreasing the levels of sexual hormones, which are protectors of health through their action on several organs of the body. Thus, this is the starting point of the organismal decay and infertility. This starting point is easily detected in women. In men, it goes under the surface, undetected, but it goes, nevertheless. Regarding fertility, aging alters the hormonal equilibrium, decreases the potential of reproductive organs, diminishes the quality of the gametes and worsen the reproductive outcomes. All these events happen at a different pace and affecting different organs in women and men. The question is what molecular pathways are involved in reproductive aging and if there is a possible halting or even reversion of the aging events. Answers to all these points will be explained in the present review.

Fructose Causes Liver Damage, Polyploidy, and Dysplasia in the Setting of Short Telomeres and p53 Loss

Studies in humans and model systems have established an important role of short telomeres in predisposing to liver fibrosis through pathways that are incompletely understood. Recent studies have shown that telomere dysfunction impairs cellular metabolism, but whether and how these metabolic alterations contribute to liver fibrosis is not well understood. Here, we investigated whether short telomeres change the hepatic response to metabolic stress induced by fructose, a sugar that is highly implicated in non-alcoholic fatty liver disease. We find that telomere shortening in telomerase knockout mice (TKO) imparts a pronounced susceptibility to fructose as reflected in the activation of p53, increased apoptosis, and senescence, despite lower hepatic fat accumulation in TKO mice compared to wild type mice with long telomeres. The decreased fat accumulation in TKO is mediated by p53 and deletion of p53 normalizes hepatic fat content but also causes polyploidy, polynuclearization, dysplasia, cell death, and liver damage. Together, these studies suggest that liver tissue with short telomers are highly susceptible to fructose and respond with p53 activation and liver damage that is further exacerbated when p53 is lost resulting in dysplastic changes.

Mathematical modelling of ageing acceleration of the human follicle due to oxidative stress and other factors

There is a gradual telomere shortening due to the inability of the replication machinery to copy the very ends of chromosomes. Additionally, other factors such as high levels of oxidation (free radicals or reactive oxygen species (ROS)), e.g. due to cumulated stress, inflammation or tobacco smoke, accelerate telomere shortening. In humans, the average telomere length is about 10-15 kb at birth and telomeres shorten at a pace of 70 bp per year. However, when cells are exposed to ROS, telomere attrition happens at a faster pace, generating a wide variety of telomere size distribution in different length percentiles, which are different to what is expected just by age. In this work, the generational age of a cell is associated with its telomere length (TL), from certain maximum to the minimal TL that allows replication. In order to study the accumulation of aged granulosa cells in human follicles, from preantral to preovulatory size, a mathematical model is proposed, regarding different degrees of accelerated telomere shortening, which reflect the action of ROS in addition to the telomere shortening that happens after cell division. In cases of cells with TL shorter than cells with average TL, with low telomerase activity and accelerated telomere shortening, the mathematical model predicts an aged outcome in preovulatory follicles. The model provides a plausible explanation for what has been observed in oocytes from older women, which have been exposed to ROS for a longer period of time and have bad outcomes after in vitro fertilization.

On Broken Ne(c)ks and Broken DNA: The Role of Human NEKs in the DNA Damage Response

NIMA-related kinases, or NEKs, are a family of Ser/Thr protein kinases involved in cell cycle and mitosis, centrosome disjunction, primary cilia functions, and DNA damage responses among other biological functional contexts in vertebrate cells. In human cells, there are 11 members, termed NEK1 to 11, and the research has mainly focused on exploring the more predominant roles of NEKs in mitosis regulation and cell cycle. A possible important role of NEKs in DNA damage response (DDR) first emerged for NEK1, but recent studies for most NEKs showed participation in DDR. A detailed analysis of the protein interactions, phosphorylation events, and studies of functional aspects of NEKs from the literature led us to propose a more general role of NEKs in DDR. In this review, we express that NEK1 is an activator of ataxia telangiectasia and Rad3-related (ATR), and its activation results in cell cycle arrest, guaranteeing DNA repair while activating specific repair pathways such as homology repair (HR) and DNA double-strand break (DSB) repair. For NEK2, 6, 8, 9, and 11, we found a role downstream of ATR and ataxia telangiectasia mutated (ATM) that results in cell cycle arrest, but details of possible activated repair pathways are still being investigated. NEK4 shows a connection to the regulation of the nonhomologous end-joining (NHEJ) repair of DNA DSBs, through recruitment of DNA-PK to DNA damage foci. NEK5 interacts with topoisomerase IIβ, and its knockdown results in the accumulation of damaged DNA. NEK7 has a regulatory role in the detection of oxidative damage to telomeric DNA. Finally, NEK10 has recently been shown to phosphorylate p53 at Y327, promoting cell cycle arrest after exposure to DNA damaging agents. In summary, this review highlights important discoveries of the ever-growing involvement of NEK kinases in the DDR pathways. A better understanding of these roles may open new diagnostic possibilities or pharmaceutical interventions regarding the chemo-sensitizing inhibition of NEKs in various forms of cancer and other diseases.

Targeting senescent cells and tumor therapy (Review)

Cell senescence is caused by the activation of cell cycle inhibition pathways induced by an accumulation of cellular damage, where cells permanently leave the cell cycle. Senescent cells undergo changes in cell morphology, transcription, protein homeostasis, metabolism and other characteristic alterations. At the same time, senescent cells are able to resist apoptosis and accumulate in multiple organs and tissues in vivo. Senescent cells are capable of activating inflammatory factor secretion pathways, generating local, non-infectious inflammatory microenvironments within tissues, leading to organ degeneration and the development of aging-associated diseases. A large number of recently published studies have demonstrated that removing senescent cells from the body delays the occurrence of various aging-associated diseases. Therefore, the targeted killing of senescent cells potentially has important clinical applications in the treatment of various aging-associated diseases, aiming to improve the life span of patients. The present review summarizes recent progress that has been made in the field of senescent cell clearance and various anti-aging strategies. The history of cell senescence research is briefly reviewed, along with the association between cell senescence and tumor therapy. Furthermore, the potential of senescent cells to be used as therapeutic targets in various senescence-associated diseases is primarily discussed, and the limitations, as well as the future prospects of this line of research, are reviewed.

Shelterin Complex at Telomeres: Implications in Ageing

Different factors influence the development‎ and control of ageing. It is well known that progressive telomere shorting is one of the molecular mechanisms underlying ageing. The shelterin complex consists of six telomere-specific proteins which are involved in the protection of chromosome ends. More particularly, this vital complex protects the telomeres from degradation, prevents from activation of unwanted repair systems, regulates the activity of telomerase, and has a crucial role in cellular senescent and ageing-related pathologies. This review explores the organization and function of telomeric DNA along with the mechanism of telomeres during ageing, followed by a discussion of the critical role of shelterin components and their changes during ageing.

Comparative Transcriptomics Reveals Patterns of Adaptive Evolution Associated with Depth and Age Within Marine Rockfishes (Sebastes)

The genetic underpinnings that contribute to ecological adaptation and speciation are not completely understood, especially within marine ecosystems. These evolutionary processes can be elucidated by studying adaptive radiations, because they provide replicates of divergence within a given environment or time-frame. Marine rockfishes (genus Sebastes) are an adaptive radiation and unique model system for studying adaptive evolution in the marine realm. We investigated molecular evolution associated with ecological (depth) and life history (lifespan) divergence in 2 closely related clades of Sebastes. Brain transcriptomes were sequenced via RNA-Seq from 3 species within the subgenus Pteropodus and a pair of related congeners from the subgenus Sebastosomus in order to identify patterns of adaptive evolution. De novo assemblies from these transcriptomes were used to identify 3867 orthologous clusters, and genes subject to positive selection were identified based on all 5 species, depth, and lifespan. Within all our analyses, we identified hemoglobin subunit α to be under strong positive selection and is associated with the depth of occurrence. In our lifespan analysis we identified immune function genes under positive selection in association with maximum lifespan. This study provides insight on the molecular evolution of rockfishes and these candidate genes may provide a better understanding of how these subgenera radiated within the Northeast Pacific.

Distinct telomere length and molecular signatures in seminoma and non-seminoma of testicular germ cell tumor

Testicular germ cell tumors (TGCTs) are classified into two main subtypes, seminoma (SE) and non-seminoma (NSE), but their molecular distinctions remain largely unexplored. Here, we used expression data for mRNAs and microRNAs (miRNAs) from The Cancer Genome Atlas (TCGA) to perform a systematic investigation to explain the different telomere length (TL) features between NSE (n = 48) and SE (n = 55). We found that TL elongation was dominant in NSE, whereas TL shortening prevailed in SE. We further showed that both mRNA and miRNA expression profiles could clearly distinguish these two subtypes. Notably, four telomere-related genes (TelGenes) showed significantly higher expression and positively correlated with telomere elongation in NSE than SE: three telomerase activity-related genes (TERT, WRAP53 and MYC) and an independent telomerase activity gene (ZSCAN4). We also found that the expression of genes encoding Yamanaka factors was positively correlated with telomere lengthening in NSE. Among them, SOX2 and MYC were highly expressed in NSE versus SE, while POU5F1 and KLF4 had the opposite patterns. These results suggested that enhanced expression of both TelGenes (TERT, WRAP53, MYC and ZSCAN4) and Yamanaka factors might induce telomere elongation in NSE. Conversely, the relative lack of telomerase activation and low expression of independent telomerase activity pathway during cell division may be contributed to telomere shortening in SE. Taken together, our results revealed the potential molecular profiles and regulatory roles involving the TL difference between NSE and SE, and provided a better molecular understanding of this complex disease.

Clinical utility of telomere length measurements in cancer

Cancer remains one of the leading causes of death in the developed world and despite impressive advances in therapeutic modalities, only a small subset of patients are currently cured. The underlying genetic heterogeneity of cancers clearly plays a crucial role in determining both the clinical course of individual pathologies and their responses to standard treatments. Although every tumour is to some extent distinct, there are recurrent features of cancers that can be exploited as therapeutic targets and as prognostic and predictive biomarkers; one such attribute is telomere length. Here we discuss the utility of telomere length evaluation in cancer and describe some of the promise and challenges of bringing this into clinical practice.

Inhibition of DNA Methyltransferase by RG108 Promotes Pluripotency-Related Character of Porcine Bone Marrow Mesenchymal Stem Cells

Mesenchymal stem/stromal cells (MSCs) have been identified in almost all adult human tissues and been used in numerous clinical trials for a variety of diseases. Studies have shown that MSCs would undergo cellular senescence when cultured over a long term, which is brought on by increased epigenetic modifications, including DNA methylation. However, the mechanism of MSCs senescence is not well studied. In this study, the effects of RG108, a DNA methyltransferase inhibitor (DNMTi), on senescence, apoptosis, and pluripotency gene expressions in porcine bone marrow (pBM)-MSCs were investigated. First, we determined the optimized dose and time of RG108 treatment in pBM-MSCs to be 10 μM for 48 hours, respectively. Under these conditions, the pluripotency genes (NANOG, POU5F1), the anti-senescence genes (TERT, bFGF), and the anti-apoptosis gene (BCL2) were increased, whereas the apoptotic gene (BAX) was decreased. RG108 protected against apoptosis when pBM-MSC induces apoptosis with H₂O₂ for 1.5 hours. We also found that RG108 significantly induced the expression of NANOG and POU5F1 by decreasing DNA methylation in gene promoter regions. These results indicate that an optimized dose of RG108 may promote the pluripotency-related character of pBM-MSCs through improving cellular anti-senescence, anti-apoptosis, and pluripotency, which provide a better cell origin for stem cell therapy.

Endothelial senescence-associated secretory phenotype (SASP) is regulated by Makorin-1 ubiquitin E3 ligase

BACKGROUND

Disturbed flow (d-flow)-induced senescence and activation of endothelial cells (ECs) have been suggested to have critical roles in promoting atherosclerosis. Telomeric repeat-binding factor 2 (TERF2)-interacting protein (TERF2IP), a member of the shelterin complex at the telomere, regulates the senescence-associated secretory phenotype (SASP), in which EC activation and senescence are engendered simultaneously by p90RSK-induced phosphorylation of TERF2IP S205 and subsequent nuclear export of the TERF2IP-TERF2 complex. In this study, we investigated TERF2IP-dependent gene expression and its role in regulating d-flow-induced SASP.

METHODS

A principal component analysis and hierarchical clustering were used to identify genes whose expression is regulated by TERF2IP in ECs under d-flow conditions. Senescence was determined by reduced telomere length, increased p53 and p21 expression, and increased apoptosis; EC activation was detected by NF-κB activation and the expression of adhesion molecules. The involvement of TERF2IP S205 phosphorylation in d-flow-induced SASP was assessed by depletion of TERF2IP and mutation of the phosphorylation site.

RESULTS

Our unbiased transcriptome analysis showed that TERF2IP caused alteration in the expression of a distinct set of genes, including rapamycin-insensitive companion of mTOR (RICTOR) and makorin-1 (MKRN1) ubiquitin E3 ligase, under d-flow conditions. In particular, both depletion of TERF2IP and overexpression of the TERF2IP S205A phosphorylation site mutant in ECs increased the d-flow and p90RSK-induced MKRN1 expression and subsequently inhibited apoptosis, telomere shortening, and NF-κB activation in ECs via suppression of p53, p21, and telomerase (TERT) induction.

CONCLUSIONS

MKRN1 and RICTOR belong to a distinct reciprocal gene set that is both negatively and positively regulated by p90RSK. TERF2IP S205 phosphorylation, a downstream event of p90RSK activation, uniquely inhibits MKRN1 expression and contributes to EC activation and senescence, which are key events for atherogenesis.

Epigallocatechin-3-gallate induces telomere shortening and clastogenic damage in glioblastoma cells

Epigallocatechingallate (EGCG) is the major polyphenol in green tea, to which many anticancer features, such as antioxidative, antigenotoxic, and antiangiogenetic properties, are attributed. Moreover, it is also well known as a telomerase inhibitor. In this work, we have chronically treated U251 glioblastoma cells with low, physiologically realistic concentrations, of EGCG, in order to investigate its effects both on telomeres and on genome integrity. Inhibition of telomerase activity caused telomere shortening, ultimately leading to senescence and telomere dysfunction at 98 days. Remarkably, we have observed DNA damage through an increase of phosphorylation of γ-H2AX histone and micronuclei also with doses and at timepoints when telomere shortening was not present. Therefore, we concluded that this DNA damage was not correlated with telomere shortening and that EGCG treatment induced not only an increase of telomere-shortening-induced senescence but also telomere-independent genotoxicity. This study questions the common knowledge about EGCG properties, but confirms the few works that indicated the clastogenic properties of this molecule, probably due to DNA reductive damage and topoisomerase II poisoning. Environ. Mol. Mutagen., 60:683-692, 2019. © 2019 Wiley Periodicals, Inc.

Association between hTERT Polymorphisms and Female Papillary Thyroid Carcinoma

BACKGROUND

A previous genome-wide association study showed that hTERT rs10069690 and rs2736100 polymorphisms were associated with thyroid cancer risk.

OBJECTIVE

This study further investigated the association between increased risk and clinicopathologic characteristics for Papillary Thyroid Carcinoma (PTC) and hTERT polymorphisms rs10069690 or rs2736100 in a Chinese female population.

METHODS

The hTERT genotypes of 276 PTC patients and 345 healthy subjects were determined with regard to SNPs rs10069690 and rs2736100. The association between these SNPs and the risk of PTC and clinicopathologic characteristics was investigated by logistic regression.

RESULTS

We found a significant difference between PTC and rs10069690 (Odds Ratio (OR) = 1.515; P = 0.005), but not between PTC and rs2736100. When the analysis was limited to females, rs10069690 and rs2736100 were both associated with increased risk for PTC in female individuals (OR = 1.647, P = 0.007; OR = 1.339, P = 0.041, respectively). Further haplotype analysis revealed a stimulative effect of haplotypes TC and CA of TERT rs10069690-rs2736100, which increased risk for PTC in female individuals (OR = 1.579, P = 0.014; OR = 0.726, P = 0.025, respectively). Furthermore, the heterozygote A/C of rs2736100 showed significant difference for age (OR = 0.514, P = 0.047).

CONCLUSION

Our finding suggests that hTERT polymorphisms rs10069690 and rs2736100 are associated with increased risk for PTC in Chinese female population and rs2736100 may be related to age. Consistent with US20170360914 and US20170232075, they are expected to be a potential molecular target for anti-cancer therapy.

Telomere length and cancer mortality in American Indians: the Strong Heart Study

The objective of this study was to investigate whether leukocyte telomere length (LTL) predicts the risk for cancer mortality among American Indians participating in the Strong Heart Study (1989-1991). Participants (aged 45-74 years) were followed annually until December 2015 to collect information on morbidity/mortality. LTL was measured by qPCR using genomic DNA isolated from peripheral blood. The association between LTL and risk for cancer mortality was examined using a multivariable Cox proportional hazard model, adjusting for age, gender, education, study site, smoking, alcohol use, physical activity, systolic blood pressure, fasting blood glucose, obesity, and low- and high-density lipoprotein. Of 1945 participants (mean age 56.10 ± 8.17 at baseline, 57% women) followed for an average 20.5 years, 220 died of cancer. Results showed that longer LTL at baseline significantly predicts an increased risk of cancer death among females (HR 1.57, 95% CI 1.08-2.30), but not males (HR 0.74, 95% CI 0.49-1.12) (p for interaction 0.009). Specifically, compared with the women with the longest LTL (fourth quartile), those in the third, second, and first quartiles showed 53%, 41%, and 44% reduced risk for cancer death, respectively. The findings highlight the importance of sex-specific analysis in future telomere research.

Association between leukocyte telomere length and hostility in US army service members

Hostility is a common form of emotionally charged anger which can lead to maladaptive and unhealthy behaviors. Significant association between shortened telomeres and greater levels of hostility has been observed in civilian populations, but has not yet been comprehensively studied in military populations. Our study investigates the relationship between hostility, post-traumatic stress disorder (PTSD), and leukocyte telomere length (LTL) in a sample of United States Army Special Operations personnel (n = 474) who deployed to Iraq and/or Afghanistan as part of combat operations. Hostility was measured with five items from the Brief Symptom Inventory (BSI). PTSD was determined using the PTSD Checklist (PCL) total score. The LTL was assessed using quantitative polymerase chain reaction methods and regression analyses were conducted to determine the association of hostility and telomere length. PTSD subjects reported higher hostility scores compared with those without PTSD. Among the participants with PTSD, those with medium or high level of hostility had shorter LTL than those with low level hostility (P < 0.01). Stepwise regression indicated that hostility level and age, but not gender and PTSD, were negatively correlated with LTL. Univariate regression showed that total hostility score was negatively associated with LTL (CI= -0.06 to -0.002, Beta= -0.095, p < 0.039) as well as a significant correlation between LTL and hostility impulses (HI) (CI= -0.108 to -0.009, Beta= -0.106, p < 0.021) and hostility controlling (HC) (CI= -0.071 to -0.002, Beta= -0.095, p < 0.004). Multiple regression analyses revealed that, while HC has no significant association with LTL, HI was still negatively correlated with LTL (p = 0.021). Our data indicates that LTL is associated with HI levels. Prevention and treatment efforts designed to reduce hostility may help mitigate risk for LTL shortening, a process of cellular aging, and thus slow accelerated aged-related health outcomes.

Should we consider telomere length and telomerase activity in male factor infertility?

PURPOSE OF REVIEW

The purpose of this review is to analyze what is known to date about the relation between telomeres and male fertility, and if it is possible for telomeres, or elements related to them, to be used as new prognostic biomarkers in fertility treatment.

RECENT FINDINGS

Cells in germ series, including spermatozoids, have longer telomeres (10-20 kb), and do not seem to undergo the shortening that takes place in somatic cells with age as they present telomerase activity. Longer telomere length found in the sperm of older fathers, influences their offspring possessing cells with longer telomere length. Infertile patients have spermatozoids with shorter telomere length than fertile people, but telomere length does neither correlate with the sperm concentration, mobility or morphology, nor with the DNA fragmentation indices (DFI) of spermatozoids. Embryo quality rate and transplantable embryo rate are related with the telomere length of spermatozoids (STL), but pregnancy rates are not affected.

SUMMARY

Telomere length and telomerase levels can be used as biomarkers of male fertility. Higher STL can have beneficial effects on fertility, thus the use of spermatozoids with longer telomere length in an assisted reproduction technique (ART) could be one way of solving some infertility cases.

Reflections on telomere dynamics and ageing-related diseases in humans

Epidemiological studies have principally relied on measurements of telomere length (TL) in leucocytes, which reflects TL in other somatic cells. Leucocyte TL (LTL) displays vast variation across individuals—a phenomenon already observed in newborns. It is highly heritable, longer in females than males and in individuals of African ancestry than European ancestry. LTL is also longer in offspring conceived by older men. The traditional view regards LTL as a passive biomarker of human ageing. However, new evidence suggests that a dynamic interplay between selective evolutionary forces and TL might result in trade-offs for specific health outcomes. From a biological perspective, an active role of TL in ageing-related human diseases could occur because short telomeres increase the risk of a category of diseases related to restricted cell proliferation and tissue degeneration, including cardiovascular disease, whereas long telomeres increase the risk of another category of diseases related to increased proliferative growth, including major cancers. To understand the role of telomere biology in ageing-related diseases, it is essential to expand telomere research to newborns and children and seek further insight into the underlying causes of the variation in TL due to ancestry and geographical location.

This article is part of the theme issue ‘Understanding diversity in telomere dynamics’.

Comparison of several commonly used detection indicators of cell senescence

Cell senescence is the state of irreversible growth arrest that can be triggered by a variety of different cellular stresses. Currently, the commonly used detection indicators involved in the study of cell senescence include senescence-associated β-galactosidase, Clusterin, Telomeres/Telomerase, senescence-associated heterochromatin foci, senescence-associated secretory phenotype, senescence marker protein-30, tumor suppressor genes p53 and p16, and other indicators such as Ki67 and decoy receptor 2. These indicators are widely used in the study of cell senescence, each with its own characteristics, advantages, and disadvantages. This review summarizes several commonly used cell senescence indicators and compares their accuracy, credibility, specificity, and the scope of their potential application.

Mathematical model to study the aging of the human follicle according to the telomerase activity

The aim of this work is to study the aging rate at which human follicles reach the preovulatory state. To this end, both telomere length and telomerase activity effects on granulosa cells (GCs) aging has been studied. GCs are somatic cells which determine the development of the oocyte. A human preantral follicle takes approximately 85 days to achieve the preovulatory size, going through several stages (Gougeon, 1996). The telomere length of GCs of each class of follicles, during folliculogenesis, are modelled using a chemical master equation formalism similar to the one in Wesch et al. (2016). Seven differential ordinary systems of equations, corresponding to seven stages of the follicule maturation, concatenated in time, are considered. The mitotic and death rates are approximated by using the mean number of GCs in each class of follicles and the time they remain on each stage. The influence of different telomerase activity rates and the telomere shortening of the preovulatory follicle is studied. Some cases of infertility are associated with low levels of telomerase activity and short telomeres in GCs. The method aims at understanding how low levels of telomerase activity in preovulatory stages lead to the accumulation of aged GCs. In the case of higher telomerase activities, the mathematical model predicts a more juvenile outcome in preovulatory follicles. Juvenile GCs, could be critical for embryo development if the oocyte were fertilized, since GCs, transformed in corpus luteum, must divide and increase their size (Alila and Hansel, 1984) to sustain early pregnancy (Csapo et al., 1972).

Blood Markers in Healthy-Aged Nonagenarians: A Combination of High Telomere Length and Low Amyloidβ Are Strongly Associated With Healthy Aging in the Oldest Old

Many factors may converge in healthy aging in the oldest old, but their association and predictive power on healthy or functionally impaired aging has yet to be demonstrated. By detecting healthy aging and in turn, poor aging, we could take action to prevent chronic diseases associated with age. We conducted a pilot study comparing results of a set of markers (peripheral blood mononuclear cell or PBMC telomere length, circulating Aβ peptides, anti-Aβ antibodies, and ApoE status) previously associated with poor aging or cognitive deterioration, and their combinations, in a cohort of “neurologically healthy” (both motor and cognitive) nonagenarians (n = 20) and functionally impaired, institutionalized nonagenarians (n = 38) recruited between 2014 and 2015. We recruited 58 nonagenarians (41 women, 70.7%; mean age: 92.37 years in the neurologically healthy group vs. 94.13 years in the functionally impaired group). Healthy nonagenarians had significantly higher mean PBMC telomere lengths (mean = 7, p = 0.001), this being inversely correlated with functional impairment, and lower circulating Aβ40 (total in plasma fraction or TP and free in plasma fraction or FP), Aβ42 (TP and FP) and Aβ17 (FP) levels (FP40 131.35, p = 0.004; TP40 299.10, p = 0.007; FP42 6.29, p = 0.009; TP42 22.53, p = 0.019; FP17 1.32 p = 0.001; TP17 4.47, p = 0.3), after adjusting by age. Although healthy nonagenarians had higher anti-Aβ40 antibody levels (net adsorbed signal or NAS ± SD: 0.211 ± 0.107), the number of participants that pass the threshold (NAS > 3) to be considered as positive did not show such a strong association. There was no association with ApoE status. Additionally, we propose a “Composite Neurologically Healthy Aging Score” combining TP40 and mean PBMC telomere length, the strongest correlation of measured biomarkers with neurologically healthy status in nonagenarians (AUC = 0.904).

Effect of therapies-mediated modulation of telomere and/or telomerase on cancer cells radiosensitivity

Cancer is one of the leading causes of death in the world. Many strategies of cancer treatment such as radiotherapy which plays a key role in cancer treatment are developed and used nowadays. However, the side effects post-cancer radiotherapy and cancer radioresistance are two major causes of the limitation of cancer radiotherapy effectiveness in the cancer patients. Moreover, reduction of the limitation of cancer radiotherapy effectiveness by reducing the side effects post-cancer radiotherapy and cancer radioresistance is the aim of several radiotherapy-oncologic teams. Otherwise, Telomere and telomerase are two cells components which play an important role in cancer initiation, cancer progression and cancer therapy resistance such as radiotherapy resistance. For resolving the problems of the limitation of cancer radiotherapy effectiveness especially the cancer radio-resistance problems, the radio-gene-therapy strategy which is the use of gene-therapy via modulation of gene expression combined with radiotherapy was developed and used as a new strategy to treat the patients with cancer. In this review, we summarized the information concerning the implication of telomere and telomerase modulation in cancer radiosensitivity.

Terc is dispensable for most of the short-term HPV16 oncogene-mediated phenotypes in mice

High-risk human papillomaviruses (HPVs) have been shown in vitro to impinge on telomere homeostasis in a number of ways. However, the in vivo interaction of viruses with the telomere homeostasis apparatus has not been previously explored. Since E6 and E7 are the main viral oncogenes and key for viral replication, we have explored here the short-term phenotypes of the genes in the context of defective telomere homeostasis. We examined the short-term phenotypes of E6 and E7 in a context where the Terc component of the telomerase holoenzyme was knocked out. We determined that Terc was dispensable for most oncogene-mediated phenotypes. Surprisingly, E7-mediated reduction of label retaining cells was found to be in part dependent on the presence of Terc. Under the conditions examined here, there appears to be no compelling evidence Terc is required for most short-term viral oncogene mediated phenotypes. Further studies will elucidate its role in longer-term phenotypes.

Deletion of Rap1 disrupts redox balance and impairs endothelium-dependent relaxations

AIMS

Repressor activator protein 1 (Rap1) is conventionally known as a static structural component of the telomere, but recent evidence indicates that it exerts functions within and outside the nucleus taking part in metabolic regulation and promoting inflammatory responses. The present study investigated whether or not Rap1 deletion affects oxidative stress and nitric oxide (NO) bioavailability in the vascular wall, thus modulating endothelial function.

METHODS AND RESULTS

Vascular responsiveness was studied in wire myographs in aortae from Rap1 wildtype and knockout mice. Deletion of Rap1 impaired endothelium-dependent relaxations elicited by acetylcholine. Rap1 deficiency did not affect the activation of endothelial NO synthase or the sensitivity of vascular smooth muscle to NO donors. The blunted acetylcholine-mediated relaxations in Rap1 deficient aortae were restored with nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors, apocynin or VAS2870. Rap1 deletion lowered cellular thiol-redox status and diminished activities of thiol-redox enzymes, thioredoxin 1 and glutaredoxin 1.

CONCLUSIONS

The capacity of thioredoxin 1 and glutaredoxin 1 to reduce intra-protein disulfide bridges is weakened in Rap1 deficient mice, resulting in hyper-activation of NADPH oxidase and greater reactive oxygen species generation. The high oxidative stress in Rap1 deficient mice is implicated with greater oxidative breakdown of NO, explaining the blunted acetylcholine-mediated relaxations in this animal. These findings imply that Rap1 plays an unanticipated role in regulating the fate of NO (a pivotal determinant of vascular homeostasis) and thus identify a new physiological importance of the telomere-associated protein.

CRISPR-Cas9 Mediated Telomere Removal Leads to Mitochondrial Stress and Protein Aggregation

Aging is considered the major risk factor for neurodegenerative diseases including Parkinson’s disease (PD). Telomere shortening is associated with cellular senescence. In this regard, pharmacological or genetic inhibition of telomerase activity has been used to model cellular aging. Here, we employed CRISPR-Cas9 technology to instantly remove the telomere to induce aging in a neuroblastoma cell line. Expression of both Cas9 and guide RNA targeting telomere repeats ablated the telomere, leading to retardation of cell proliferation. Instant deletion of telomere in SH-SY5Y cells impaired mitochondrial function with diminished mitochondrial respiration and cell viability. Supporting the pathological relevance of cell aging by CRISPR-Cas9 mediated telomere removal, alterations were observed in the levels of PD-associated proteins including PTEN-induced putative kinase 1, peroxisome proliferator-activated receptor γ coactivator 1-α, nuclear respiratory factor 1, parkin, and aminoacyl tRNA synthetase complex interacting multifunctional protein 2. Significantly, α-synuclein expression in the background of telomere removal led to the enhancement of protein aggregation, suggesting positive feed-forward interaction between aging and PD pathogenesis. Collectively, our results demonstrate that CRISPR-Cas9 can be used to efficiently model cellular aging and PD.

Persistent Herpesvirus Infections and Telomere Attrition Over 3 Years in the Whitehall II Cohort

The determinants of telomere attrition, a potential marker of cellular aging, are not well understood. Persistent herpesvirus infections including cytomegalovirus (CMV) infection may be particularly important for telomere dynamics via mechanisms such as inflammation, oxidative stress, and their impact on peripheral blood lymphocyte composition. This study examined the association of 4 human herpesviruses (CMV, herpes simplex virus type 1, human herpesvirus type 6, and Epstein-Barr virus) with change in leukocyte telomere length (LTL) over 3 years in 400 healthy individuals (aged 53-76 years) from the Whitehall II cohort. CMV, herpes simplex virus type 1, and human herpesvirus 6 infection were independently associated with greater 3-year LTL attrition, with no association found for Epstein-Barr virus. The magnitudes of these associations were large, for example, the equivalent of almost 12 years of chronological age for those CMV seropositive. Seropositivity to more herpesviruses was additively associated with greater LTL attrition (3 herpesviruses vs none, β = -0.07 and P = .02; 4 infections vs none, β = -0.14 and P < .001). Higher immunoglobulin G antibody levels among those seropositive to CMV were also associated with shorter LTL at follow-up. These associations were robust to adjustment for age, sex, employment grade, body mass index, and smoking status. These results suggest that exposure to infectious agents should be an important consideration in future studies of telomere dynamics.

Regulated expression of the lncRNA TERRA and its impact on telomere biology

The telomere protects against genomic instability by minimizing the accelerated end resection of the genetic material, a phenomenon that results in severe chromosome instability that could favor the transformation of a cell by enabling the emergence of tumor-promoting mutations. Some mechanisms that avoid this fate, such as capping and loop formation, have been very well characterized; however, telomeric non-coding transcripts, such as long non-coding RNAs (lncRNAs), should also be considered in this context because they play roles in the organization of telomere dynamics, involving processes such as replication, degradation, extension, and heterochromatin stabilization. Although the mechanism through which the expression of telomeric transcripts regulates telomere dynamics is not yet clear, a non-coding RNA component opens the research options in telomere biology and the impact that it can have on telomere-associated diseases such as cancer.

Phosphorothioate‑modified antisense oligonucleotides against human telomerase reverse transcriptase sensitize cancer cells to radiotherapy

Emergence of resistance, unavoidable systemic toxicity and unsatisfactory efficacy arethe main obstacles for traditional cancer therapy. Combination with phosphorothioate modified antisense oligonucleotides (PS‑ASODN) against human telomerase reverse transcriptase (hTERT) may enhance the therapeutic effect of irradiation. However, the effect of PS‑ASODN against hTERT on the anti‑tumor effects of irradiation in liver cancer remain unclear. In the current study, Walker 256 cells were transfected with hTERT PS‑ASODN. Cell proliferation and cell viability were measured using the MTT assay and cell senescence was examined by SA‑β‑gal staining. Telomerase activity was determined by telomeric repeat amplification protocol‑polymerase chain reaction‑ELISA. Cell apoptosis was assayed by flow cytometry and DNA damage was determined by the comet assay.The PS‑ASODN was demonstrated to have an inhibitory effect on cell proliferation and accelerated effect on cell senescence by inhibiting telomerase activity. PS‑ASODN promoted the irradiation‑induced inhibition of cell viability and telomerase activity, and irradiation‑induced DNA damage and cell apoptosis via the activation of apoptosis‑associated proteins. Taken together, these results indicated that combined treatment of PS‑ASODN with irradiation significantly enhanced tumor inhibition. Therefore, PS‑ASODN provides an experimental foundation for gene therapy and is proposed for application in clinical treatment of liver cancer combined with radiotherapy.

Telomerase and N-Cadherin Differential Importance in Adrenocortical Cancers and Adenomas

Adrenocortical carcinomas (ACC) are most frequently highly aggressive tumors. We assessed the telomerase reverse transcriptase (TERT) and N-cadherin role in the biology of ACC and their potential utility as molecular biomarkers, in different types of tumoral adrenocortical tissue. A total of 48 adrenal cortex samples (39 tumoral and 9 normal adrenal glands) were studied. TERT promoter mutations were searched by PCR and Sanger sequencing in two hotspots positions (-124 and -146). Also, telomerase and N-cadherin expression were evaluated by immunohistochemistry. TERT promoter mutations were not detected in any of the samples either malignant or benign. Telomerase nuclear expression was present in 26.6% of ACC and in 45.5% of non-functioning adenomas. It was absent in benign Cushing's lesions and in normal adrenal glands. Contrarily, N-cadherin was always expressed in the cellular membranes of benign adenomas or normal adrenals but no expression was detected in the majority of ACC. Nuclear telomerase and membrane N-cadherin expression were positively correlated in ACCs. We conclude that in ACC, the loss of N-cadherin is a frequent phenomenon while the existence of TERT promoter mutations is not and nuclear telomerase expression is present in only a minority of cases. Since the loss of N-cadherin expression was identified in both high and low proliferative ACC, this marker should be considered important for diagnostic application. Our study also suggests the existence of a TERT non-canonical function in cell adhesion. J. Cell. Biochem. 118: 2064-2071, 2017. © 2017 Wiley Periodicals, Inc.

Telomerase and telomere biology in hematological diseases: A new therapeutic target

Telomeres are structures confined at the ends of eukaryotic chromosomes. With each cell division, telomeric repeats are lost because DNA polymerases are incapable to fully duplicate the very ends of linear chromosomes. Loss of repeats causes cell senescence, and apoptosis. Telomerase neutralizes loss of telomeric sequences by adding telomere repeats at the 3' telomeric overhang. Telomere biology is frequently associated with human cancer and dysfunctional telomeres have been proved to participate to genetic instability. This review covers the information on telomerase expression and genetic alterations in the most relevant types of hematological diseases. Telomere erosion hampers the capability of hematopoietic stem cells to effectively replicate, clinically resulting in bone marrow failure. Furthermore, telomerase mutations are genetic risk factors for the occurrence of some hematologic cancers. New discoveries in telomere structure and telomerase functions have led to an increasing interest in targeting telomeres and telomerase in anti-cancer therapy.

A Theory for the Origin of Human Menopause

A complete and compelling evolutionary explanation for the origin of human menopause is wanting. Menopause onset is defined clinically as the final menses, confirmed after 1 year without menstruation. The theory proposed herein explains at multiple levels - ultimately genetic but involving (1) behavioral, (2) life history, and (3) social changes - the origin and evolution of menopause in women. Individuals in Lower Paleolithic human populations were characterized by short lifespans with diminished late-age survival and fertility, similar to contemporary chimpanzees, and thence were subject to three changes. (1) A mating behavior change was established in which only young women reproduced, thereby rendering as effectively neutral female-specific late-onset fertility-diminishing mutations, which accumulated subsequently. (2) A lifespan increase was manifested adaptively, revealing the reproductive senescence phenotype encoded in late-onset fertility-diminishing mutation genotypes, which, heretofore, had been unexpressed in the shorter lifespan. (3) A social interaction change emerged exaptively, when older non-reproductive women exclusively started assisting in rearing grandchildren rather than giving birth to and caring for their own children, ultimately leading to menstrual cycle cessation. The changes associate in a one-to-one manner with existing, non-mutually exclusive hypotheses for the origin of human menopause. Evidence for each hypothesis and its associated change having occurred are reviewed, and the hypotheses are combined in a synthetic theory for the origin of human menopause. The new theory simultaneously addresses the main theoretical problem with each hypothesis and yields predictions for future testing.

Telomeres in health and disease

Telomeres are repetitive ribonucleoprotein complexes present at ends of chromosomes. To synthesize this manuscript, a thorough literature search was done using PubMed, MEDLINE and Cochrane review for English-language literature and data available from the period of 2005–2016 were analyzed for manuscript writing. Telomeres help in maintaining the cellular health, inbuilt cellular mechanisms, metabolism and normal cell cycle. Telomerase is a specialized enzyme that possesses catalytic subunits - reverse transcriptase, Terc and dyskerin. Mutations affecting telomere or any component of telomerase enzyme result in disorders such as dyskeratosis congenita, aplastic anemia, myelodysplastic syndromes and leukemias. Thus, it is important to understand the telomere biology so as to deal with normal physiologic processes such as apoptosis, aging and senescence and tumor development.

Interplay between Top1 and Mms21/Nse2 mediated sumoylation in stable maintenance of long chromosomes

Genetic information in cells is encrypted in DNA molecules forming chromosomes of varying sizes. Accurate replication and partitioning of chromosomes in the crowded cellular milieu is a complex process involving duplication, folding and movement. Longer chromosomes may be more susceptible to mis-segregation or DNA damage and there may exist specialized physiological mechanisms preventing this. Here, we present genetic evidence for such a mechanism which depends on Mms21/Nse2 mediated sumoylation and topoisomerase-1 (Top1) for maintaining stability of longer chromosomes. While mutations inactivating Top1 or the SUMO ligase activity of Mms21 (mms21sl) individually destabilized yeast artificial chromosomes (YACs) to a modest extent, the mms21sl top1 double mutant exhibited a synthetic-sick phenotype, and showed preferential destabilization of the longer chromosome relative to shorter chromosomes. In contrast, an smc6-56 top1 mutant defective in Smc6, another subunit of the Smc5/6 complex, of which Mms21 is a component, did not show such a preferential enhancement in frequency of loss of the longer YAC, indicating that this defect may be specific to the deficiency in SUMO ligase activity of Mms21 in the mms21sl top1 mutants. In addition, mms21sl top1 double mutants harboring a longer fusion derivative of natural yeast chromosomes IV and XII displayed reduced viability, consistent with enhanced chromosome instability, relative to single mutants or the double mutant having the natural (shorter) non-fused chromosomes. Our findings reveal a functional interplay between Mms21 and Top1 in maintenance of longer chromosomes, and suggest that lack of sumoylation of Mms21 targets coupled with Top1 deficiency is a crucial requirement for accurate inheritance of longer chromosomes.

Fibroblast-Derived Extracellular Matrix Induces Chondrogenic Differentiation in Human Adipose-Derived Mesenchymal Stromal/Stem Cells in Vitro

Mesenchymal stromal/stem cells (MSCs) represent an area being intensively researched for tissue engineering and regenerative medicine applications. MSCs may provide the opportunity to treat diseases and injuries that currently have limited therapeutic options, as well as enhance present strategies for tissue repair. The cellular environment has a significant role in cellular development and differentiation through cell-matrix interactions. The aim of this study was to investigate the behavior of adipose-derived MSCs (ad-MSCs) in the context of a cell-derived matrix so as to model the in vivo physiological microenvironment. The fibroblast-derived extracellular matrix (fd-ECM) did not affect ad-MSC morphology, but reduced ad-MSC proliferation. Ad-MSCs cultured on fd-ECM displayed decreased expression of integrins α2 and β1 and subsequently lost their multipotency over time, as shown by the decrease in CD44, Octamer-binding transcription factor 4 (OCT4), SOX2, and NANOG gene expression. The fd-ECM induced chondrogenic differentiation in ad-MSCs compared to control ad-MSCs. Loss of function studies, through the use of siRNA and a mutant Notch1 construct, revealed that ECM-mediated ad-MSCs chondrogenesis requires Notch1 and β-catenin signaling. The fd-ECM also showed anti-senescence effects on ad-MSCs. The fd-ECM is a promising approach for inducing chondrogenesis in ad-MSCs and chondrogenic differentiated ad-MSCs could be used in stem cell therapy procedures.