Measuring vertebrate telomeres: applications and limitations

Telomeres are short tandem repeated sequences of DNA found at the ends of eukaryotic chromosomes that function in stabilizing chromosomal end integrity. In vivo studies of somatic tissue of mammals and birds have shown a correlation between telomere length and organismal age within species, and correlations between telomere shortening rate and lifespan among species. This result presents the tantalizing possibility that telomere length could be used to provide much needed information on age, ageing and survival in natural populations where longitudinal studies are lacking. Here we review methods available for measuring telomere length and discuss the potential uses and limitations of telomeres as age and ageing estimators in the fields of vertebrate ecology, evolution and conservation

Aberrant Epigenetic Silencing Is Triggered by a Transient Reduction in Gene Expression

Aberrant epigenetic silencing plays a major role in cancer formation by inactivating tumor suppressor genes. While the endpoints of aberrant silencing are known, i.e., promoter region DNA methylation and altered histone modifications, the triggers of silencing are not known. We used the tet-off system to test the hypothesis that a transient reduction in gene expression will sensitize a promoter to undergo epigenetic silencing.The tet responsive promoter (P(TRE)) was used to drive expression of the selectable human HPRT cDNA in independent transfectants of an Hprt deficient mouse cell line. In this system, high basal HPRT expression is greatly reduced when doxycycline (Dox) is added to the culture medium. Exposure of the P(TRE)-HPRT transfectants to Dox induced HPRT deficient clones in a time dependent manner. A molecular analysis demonstrated promoter region DNA methylation, loss of histone modifications associated with expression (i.e., H3 lysine 9 and 14 acetylation and lysine 4 methylation), and acquisition of the repressive histone modification H3 lysine 9 methylation. These changes, which are consistent with aberrant epigenetic silencing, were not present in the Dox-treated cultures, with the exception of reduced H3 lysine 14 acetylation. Silenced alleles readily reactivated spontaneously or after treatment of cells with inhibitors of histone deacetylation and/or DNA methylation, but re-silencing of reactivated alleles did not require a new round of Dox exposure. Inhibition of histone deacetylation inhibited both the induction of silencing and re-silencing, whereas inhibition of DNA methylation had no such effect.This study demonstrates that a transient reduction in gene expression triggers a pathway for aberrant silencing in mammalian cells and identifies histone deacetylation as a critical early step in this process. DNA methylation, in contrast, is a secondary step in the silencing pathway under study. A model to explain these observations is offered

VEZF1 elements mediate protection from DNA methylation

There is growing consensus that genome organization and long-range gene regulation involves partitioning of the genome into domains of distinct epigenetic chromatin states. Chromatin insulator or barrier elements are key components of these processes as they can establish boundaries between chromatin states. The ability of elements such as the paradigm β-globin HS4 insulator to block the range of enhancers or the spread of repressive histone modifications is well established. Here we have addressed the hypothesis that a barrier element in vertebrates should be capable of defending a gene from silencing by DNA methylation. Using an established stable reporter gene system, we find that HS4 acts specifically to protect a gene promoter from de novo DNA methylation. Notably, protection from methylation can occur in the absence of histone acetylation or transcription. There is a division of labor at HS4; the sequences that mediate protection from methylation are separable from those that mediate CTCF-dependent enhancer blocking and USF-dependent histone modification recruitment. The zinc finger protein VEZF1 was purified as the factor that specifically interacts with the methylation protection elements. VEZF1 is a candidate CpG island protection factor as the G-rich sequences bound by VEZF1 are frequently found at CpG island promoters. Indeed, we show that VEZF1 elements are sufficient to mediate demethylation and protection of the APRT CpG island promoter from DNA methylation. We propose that many barrier elements in vertebrates will prevent DNA methylation in addition to blocking the propagation of repressive histone modifications, as either process is sufficient to direct the establishment of an epigenetically stable silent chromatin stat

Towards a Model of Corporate and Social Stakeholder Engagement: Analyzing the Relations Between a French Mutual Bank and Its Members

International audienceThe aim of this article is to develop a new classification of stakeholders based on the concept of corporate and social engagement. Engagement is analyzed as an organizational learning process between the managers of an organization and its stakeholders. It is a necessary condition to improve the organization's impact on its economic, social, and natural environment. Applied to the membership of a French mutual bank in order to identify the members' varying levels of engagement, this new mapping technique may help managers to adapt their practices to the degree of engagement of each identified group of members, and to modify their financial products and communications to foster engagement among as many of these groups as possible

How Do Employees Perceive Corporate Responsibility? Development and Validation of a Multidimensional Corporate Stakeholder Responsibility Scale

Recent research on the microfoundations of corporate social responsibility (CSR) has highlighted the need for improved measures to evaluate how stakeholders perceive and subsequently react to CSR initiatives. Drawing on stakeholder theory and data from five samples of employees (N = 3,772), the authors develop and validate a new measure of corporate stakeholder responsibility (CStR), which refers to an organization’s context-specific actions and policies designed to enhance the welfare of various stakeholder groups by accounting for the triple bottom line of economic, social, and environmental performance; it is conceptualized as a superordinate, multidimensional construct. Results from exploratory factor analyses, first- and second-order confirmatory factor analyses, and structural equation modeling provide strong evidence of the convergent, discriminant, incremental, and criterion-related validities of the proposed CStR scale. Two-wave longitudinal studies further extend prior theory by demonstrating that the higher-order CStR construct relates positively and directly to organizational pride and perceived organizational support, as well as positively and indirectly to organizational identification, job satisfaction, and affective commitment, beyond the contribution of overall organizational justice, ethical climate, and prior measures of perceived CSR

An Sp1/Sp3 Binding Polymorphism Confers Methylation Protection

Hundreds of genes show aberrant DNA hypermethylation in cancer, yet little is known about the causes of this hypermethylation. We identified RIL as a frequent methylation target in cancer. In search for factors that influence RIL hypermethylation, we found a 12-bp polymorphic sequence around its transcription start site that creates a long allele. Pyrosequencing of homozygous tumors revealed a 2.1-fold higher methylation for the short alleles (P<0.001). Bisulfite sequencing of cancers heterozygous for RIL showed that the short alleles are 3.1-fold more methylated than the long (P<0.001). The comparison of expression levels between unmethylated long and short EBV-transformed cell lines showed no difference in expression in vivo. Electrophorectic mobility shift assay showed that the inserted region of the long allele binds Sp1 and Sp3 transcription factors, a binding that is absent in the short allele. Transient transfection of RIL allele-specific transgenes showed no effects of the additional Sp1 site on transcription early on. However, stable transfection of methylation-seeded constructs showed gradually decreasing transcription levels from the short allele with eventual spreading of de novo methylation. In contrast, the long allele showed stable levels of expression over time as measured by luciferase and ∼2–3-fold lower levels of methylation by bisulfite sequencing (P<0.001), suggesting that the polymorphic Sp1 site protects against time-dependent silencing. Our finding demonstrates that, in some genes, hypermethylation in cancer is dictated by protein-DNA interactions at the promoters and provides a novel mechanism by which genetic polymorphisms can influence an epigenetic state

The development of a stakeholder-based scale for measuring corporate social responsibility in the banking industry.

ABSTRACT: Research on corporate social responsibility (CSR) has notably increased in recent years and many scales for measuring CSR image have been developed in academic literature. Due to the contextual character recognized in the implementation of CSR strategies, in this paper a new scale based on stakeholder theory is developed to evaluate customers’ perception regarding the CSR performance of their banking service providers. The proposal of reliable measurement tools for evaluating customers’ perception is especially relevant for companies because of their significant role in influencing the design and implementation of corporate strategies. Results demonstrate the reliability and validity of this new scale in two different samples. In the banking industry, CSR includes corporate responsibilities toward customers, shareholders, employees, society, and all legal and ethical requirements of banking institutions. Nevertheless, different kinds of banking institutions have specific CSR images, which reveal different strategic approaches to CSR

DNA repair modulates the vulnerability of the developing brain to alkylating agents

Neurons of the developing brain are especially vulnerable to environmental agents that damage DNA (i.e., genotoxicants), but the mechanism is poorly understood. The focus of the present study is to demonstrate that DNA damage plays a key role in disrupting neurodevelopment. To examine this hypothesis, we compared the cytotoxic and DNA damaging properties of the methylating agents methylazoxymethanol (MAM) and dimethyl sulfate (DMS) and the mono- and bifunctional alkylating agents chloroethylamine (CEA) and nitrogen mustard (HN2), in granule cell neurons derived from the cerebellum of neonatal wild type mice and three transgenic DNA repair strains. Wild type cerebellar neurons were significantly more sensitive to the alkylating agents DMS and HN2 than neuronal cultures treated with MAM or the half-mustard CEA. Parallel studies with neuronal cultures from mice deficient in alkylguanine DNA glycosylase (Aag[superscript −/−]) or O6-methylguanine methyltransferase (Mgmt[superscript −/−]), revealed significant differences in the sensitivity of neurons to all four genotoxicants. Mgmt−/− neurons were more sensitive to MAM and HN2 than the other genotoxicants and wild type neurons treated with either alkylating agent. In contrast, Aag[superscript −/−] neurons were for the most part significantly less sensitive than wild type or Mgmt[superscript −/−] neurons to MAM and HN2. Aag[superscript −/−] neurons were also significantly less sensitive than wild type neurons treated with either DMS or CEA. Granule cell development and motor function were also more severely disturbed by MAM and HN2 in Mgmt[superscript −/−] mice than in comparably treated wild type mice. In contrast, cerebellar development and motor function were well preserved in MAM-treated Aag[superscript −/−] or MGMT-overexpressing (Mgmt[superscript Tg+]) mice, even as compared with wild type mice suggesting that AAG protein increases MAM toxicity, whereas MGMT protein decreases toxicity. Surprisingly, neuronal development and motor function were severely disturbed in Mgmt[superscript Tg+] mice treated with HN2. Collectively, these in vitro and in vivo studies demonstrate that the type of DNA lesion and the efficiency of DNA repair are two important factors that determine the vulnerability of the developing brain to long-term injury by a genotoxicant.United States. Army Medical Research and Materiel Command (Contract/Grant/Intergovernmental Project Order DAMD 17-98-1-8625)United States. National Institutes of Health (grants CA075576)United States. National Institutes of Health (RO1 C63193)United States. National Institutes of Health (P30 CA043703