The Caenorhabditis elegans LET-418/Mi2 plays a conserved role in lifespan regulation

Therapeutic effects of resveratrol on epigenetic mechanisms in age-related diseases: A comprehensive review

Recently, various studies have shown that epigenetic changes are associated with aging and age-related diseases. Both animal and human models have revealed that epigenetic processes are involved in aging mechanisms. These processes happen at multiple levels and include histone modification, DNA methylation, and changes in noncoding RNA expression. Consequently, changes in the organization of chromatin and DNA accessibility lead to the regulation of gene expression. With increasing awareness of the pivotal function of epigenetics in the aging process, researchers' attention has been drawn to how these epigenetic changes can be modified to prevent, stop, or reverse aging, senescence, and age-related diseases. Among various agents that can affect epigenetic, polyphenols are well-known phytochemicals found in fruits, vegetables, and plants. Polyphenols are found to modify epigenetic-related mechanisms in various diseases and conditions, such as metabolic disorders, obesity, neurodegenerative diseases, cancer, and cardiovascular diseases. Resveratrol (RSV) is a member of the stilbene subgroup of polyphenols which is derived from various plants, such as grapes, apples, and blueberries. Therefore, herein, we aim to summarize how RSV affects different epigenetic processes to change aging-related mechanisms. Furthermore, we discuss its roles in age-related diseases, such as Alzheimer's, Parkinson's, osteoporosis, and cardiovascular diseases.

The chromatin factors SET-26 and HCF-1 oppose the histone deacetylase HDA-1 in longevity and gene regulation in C. elegans

SET-26, HCF-1, and HDA-1 are highly conserved chromatin factors with key roles in development and aging. Here we present mechanistic insights into how these factors regulate gene expression and modulate longevity in C. elegans. We show that SET-26 and HCF-1 cooperate to regulate a common set of genes, and both antagonize the histone deacetylase HDA-1 to limit longevity. HCF-1 localization at chromatin is largely dependent on functional SET-26, whereas SET-26 is only minorly affected by loss of HCF-1, suggesting that SET-26 could recruit HCF-1 to chromatin. HDA-1 opposes SET-26 and HCF-1 on the regulation of a subset of their common target genes and in longevity. Our findings suggest that SET-26, HCF-1, and HDA-1 comprise a mechanism to fine-tune gene expression and longevity and likely have important implications for the mechanistic understanding of how these factors function in diverse organisms, particularly in aging biology.

Regulation of adipogenesis by histone methyltransferases

Epigenetic regulation is a critical component of lineage determination. Adipogenesis is the process through which uncommitted stem cells or adipogenic precursor cells differentiate into adipocytes, the most abundant cell type of the adipose tissue. Studies examining chromatin modification during adipogenesis have provided further understanding of the molecular blueprint that controls the onset of adipogenic differentiation. Unlike histone acetylation, histone methylation has context dependent effects on the activity of a transcribed region of DNA, with individual or combined marks on different histone residues providing distinct signals for gene expression. Over half of the 42 histone methyltransferases identified in mammalian cells have been investigated in their role during adipogenesis, but across the large body of literature available, there is a lack of clarity over potential correlations or emerging patterns among the different players. In this review, we will summarize important findings from studies published in the past 15 years that have investigated the role of histone methyltransferases during adipogenesis, including both protein arginine methyltransferases (PRMTs) and lysine methyltransferases (KMTs). We further reveal that PRMT1/4/5, H3K4 KMTs (MLL1, MLL3, MLL4, SMYD2 and SET7/9) and H3K27 KMTs (EZH2) all play positive roles during adipogenesis, while PRMT6/7 and H3K9 KMTs (G9a, SUV39H1, SUV39H2, and SETDB1) play negative roles during adipogenesis.

Chromatin: the old and young of it

Aging affects nearly all aspects of our cells, from our DNA to our proteins to how our cells handle stress and communicate with each other. Age-related chromatin changes are of particular interest because chromatin can dynamically respond to the cellular and organismal environment, and many modifications at chromatin are reversible. Changes at chromatin occur during aging, and evidence from model organisms suggests that chromatin factors could play a role in modulating the aging process itself, as altering proteins that work at chromatin often affect the lifespan of yeast, worms, flies, and mice. The field of chromatin and aging is rapidly expanding, and high-resolution genomics tools make it possible to survey the chromatin environment or track chromatin factors implicated in longevity with precision that was not previously possible. In this review, we discuss the state of chromatin and aging research. We include examples from yeast, Drosophila, mice, and humans, but we particularly focus on the commonly used aging model, the worm Caenorhabditis elegans, in which there are many examples of chromatin factors that modulate longevity. We include evidence of both age-related changes to chromatin and evidence of specific chromatin factors linked to longevity in core histones, nuclear architecture, chromatin remodeling, and histone modifications.

Genomic Instability and Epigenetic Changes during Aging

Aging is considered the deterioration of physiological functions along with an increased mortality rate. This scientific review focuses on the central importance of genomic instability during the aging process, encompassing a range of cellular and molecular changes that occur with advancing age. In particular, this revision addresses the genetic and epigenetic alterations that contribute to genomic instability, such as telomere shortening, DNA damage accumulation, and decreased DNA repair capacity. Furthermore, the review explores the epigenetic changes that occur with aging, including modifications to histones, DNA methylation patterns, and the role of non-coding RNAs. Finally, the review discusses the organization of chromatin and its contribution to genomic instability, including heterochromatin loss, chromatin remodeling, and changes in nucleosome and histone abundance. In conclusion, this review highlights the fundamental role that genomic instability plays in the aging process and underscores the need for continued research into these complex biological mechanisms.

The chromatin factors SET-26 and HCF-1 oppose the histone deacetylase HDA-1 in longevity and gene regulation in C. elegans

SET-26, HCF-1, and HDA-1 are highly conserved chromatin factors with key roles in development and aging. Here we present mechanistic insights into how these factors regulate gene expression and modulate longevity in C. elegans. We show that SET-26 and HCF-1 cooperate to regulate a common set of genes, and both antagonize the histone deacetylase HDA-1 to limit longevity. We propose a model in which SET-26 recruits HCF-1 to chromatin in somatic cells, where they stabilize each other at the promoters of a subset of genes, particularly mitochondrial function genes, and regulate their expression. HDA-1 opposes SET-26 and HCF-1 on the regulation of a subset of their common target genes and in longevity. Our findings suggest that SET-26, HCF-1, and HDA-1 comprise a mechanism to fine-tune gene expression and longevity and likely have important implications for the mechanistic understanding of how these factors function in diverse organisms, particularly in aging biology.

Systematic characterization of chromodomain proteins reveals an H3K9me1/2 reader regulating aging in C. elegans

The chromatin organization modifier domain (chromodomain) is an evolutionally conserved motif across eukaryotic species. The chromodomain mainly functions as a histone methyl-lysine reader to modulate gene expression, chromatin spatial conformation and genome stability. Mutations or aberrant expression of chromodomain proteins can result in cancer and other human diseases. Here, we systematically tag chromodomain proteins with green fluorescent protein (GFP) using CRISPR/Cas9 technology in C. elegans. By combining ChIP-seq analysis and imaging, we delineate a comprehensive expression and functional map of chromodomain proteins. We then conduct a candidate-based RNAi screening and identify factors that regulate the expression and subcellular localization of the chromodomain proteins. Specifically, we reveal an H3K9me1/2 reader, CEC-5, both by in vitro biochemistry and in vivo ChIP assays. MET-2, an H3K9me1/2 writer, is required for CEC-5 association with heterochromatin. Both MET-2 and CEC-5 are required for the normal lifespan of C. elegans. Furthermore, a forward genetic screening identifies a conserved Arginine124 of CEC-5's chromodomain, which is essential for CEC-5's association with chromatin and life span regulation. Thus, our work will serve as a reference to explore chromodomain functions and regulation in C. elegans and allow potential applications in aging-related human diseases.

Divergent regulatory roles of NuRD chromatin remodeling complex subunits GATAD2 and CHD4 in Caenorhabditis elegans

During proteotoxic stress, a pathway known as the heat shock response is induced to maintain protein-folding homeostasis or proteostasis. Previously, we identified the Caenorhabditis elegans GATAD2 ortholog, dcp-66, as a novel regulator of the heat shock response. Here, we extend these findings to show that dcp-66 positively regulates the heat shock response at the cellular, molecular, and organismal levels. As GATAD2 is a subunit of the nucleosome remodeling and deacetylase chromatin remodeling complex, we examined other nucleosome remodeling and deacetylase subunits and found that the let-418 (CHD4) nucleosome repositioning core also regulates the heat shock response. However, let-418 acts as a negative regulator of the heat shock response, in contrast to positive regulation by dcp-66. The divergent effects of these two nucleosome remodeling and deacetylase subunits extend to the regulation of other stress responses including oxidative, genotoxic, and endoplasmic reticulum stress. Furthermore, a transcriptomic approach reveals additional divergently regulated pathways, including innate immunity and embryogenesis. Taken together, this work establishes new insights into the role of nucleosome remodeling and deacetylase subunits in organismal physiology. We incorporate these findings into a molecular model whereby different mechanisms of recruitment to promoters can result in the divergent effects of nucleosome remodeling and deacetylase subunits.

Shared genetic and epigenetic changes link aging and cancer

Aging is a universal biological process that increases the risk of multiple diseases including cancer. Growing evidence shows that alterations in the genome and epigenome, driven by similar mechanisms, are found in both aged cells and cancer cells. In this review, we detail the genetic and epigenetic changes associated with normal aging and the mechanisms responsible for these changes. By highlighting genetic and epigenetic alterations in the context of tumorigenesis, cancer progression, and the aging tumor microenvironment, we examine the possible impacts of the normal aging process on malignant transformation. Finally, we examine the implications of age-related genetic and epigenetic alterations in both tumors and patients for the treatment of cancer.

Epigenetics of Aging and Aging-Associated Diseases

Aging represents the multifactorial decline in physiological function of every living organism. Over the past decades, several hallmarks of aging have been defined, including epigenetic deregulation. Indeed, multiple epigenetic events were found altered across different species during aging. Epigenetic changes directly contributing to aging and aging-related diseases include the accumulation of histone variants, changes in chromatin accessibility, loss of histones and heterochromatin, aberrant histone modifications, and deregulated expression/activity of miRNAs. As a consequence, cellular processes are affected, which results in the development or progression of several human pathologies, including cancer, diabetes, osteoporosis, and neurodegenerative disorders. In this review, we focus on epigenetic mechanisms underlying aging-related processes in various species and describe how these deregulations contribute to human diseases.

New Insights into the Role of Histone Changes in Aging

Aging is the progressive decline or loss of function at the cellular, tissue, and organismal levels that ultimately leads to death. A number of external and internal factors, including diet, exercise, metabolic dysfunction, genome instability, and epigenetic imbalance, affect the lifespan of an organism. These aging factors regulate transcriptome changes related to the aging process through chromatin remodeling. Many epigenetic regulators, such as histone modification, histone variants, and ATP-dependent chromatin remodeling factors, play roles in chromatin reorganization. The key to understanding the role of gene regulatory networks in aging lies in characterizing the epigenetic regulators responsible for reorganizing and potentiating particular chromatin structures. This review covers epigenetic studies on aging, discusses the impact of epigenetic modifications on gene expression, and provides future directions in this area.

Single-cell RNA profiling links ncRNAs to spatiotemporal gene expression during C. elegans embryogenesis

Recent studies show that non-coding RNAs (ncRNAs) can regulate the expression of protein-coding genes and play important roles in mammalian development. Previous studies have revealed that during C. elegans (Caenorhabditis elegans) embryo development, numerous genes in each cell are spatiotemporally regulated, causing the cell to differentiate into distinct cell types and tissues. We ask whether ncRNAs participate in the spatiotemporal regulation of genes in different types of cells and tissues during the embryogenesis of C. elegans. Here, by using marker-free full-length high-depth single-cell RNA sequencing (scRNA-seq) technique, we sequence the whole transcriptomes from 1031 embryonic cells of C. elegans and detect 20,431 protein-coding genes, including 22 cell-type-specific protein-coding markers, and 9843 ncRNAs including 11 cell-type-specific ncRNA markers. We induce a ncRNAs-based clustering strategy as a complementary strategy to the protein-coding gene-based clustering strategy for single-cell classification. We identify 94 ncRNAs that have never been reported to regulate gene expressions, are co-expressed with 1208 protein-coding genes in cell type specific and/or embryo time specific manners. Our findings suggest that these ncRNAs could potentially influence the spatiotemporal expression of the corresponding genes during the embryogenesis of C. elegans.

Aging mechanisms-A perspective mostly from Drosophila

A mechanistic understanding of the natural aging process, which is distinct from aging-related disease mechanisms, is essential for developing interventions to extend lifespan or healthspan. Here, we discuss current trends in aging research and address conceptual and experimental challenges in the field. We examine various molecular markers implicated in aging with an emphasis on the role of heterochromatin and epigenetic changes. Studies in model organisms have been advantageous in elucidating conserved genetic and epigenetic mechanisms and assessing interventions that affect aging. We highlight the use of Drosophila, which allows controlled studies for evaluating genetic and environmental contributors to aging conveniently. Finally, we propose the use of novel methodologies and future strategies using Drosophila in aging research.

Ageing, Drosophila melanogaster and Epigenetics

Ageing is a phenomenon where the accumulation of all the stresses that alter the functions of living organisms, halter them from maintaining their physiological balance and eventually lead to death. The emergence of epigenetic tremendously contributed to the knowledge of ageing. Epigenetic changes in cells or tissues like deoxyribonucleic acid (DNA) methylation, modification of histone proteins, transcriptional modification and also the involvement of non-coding DNA has been documented to be associated with ageing. In order to study ageing, scientists have taken advantage of several potential organisms to aid them in their study. Drosophila melanogaster has been an essential model in establishing current understanding of the mechanism of ageing as they possess several advantages over other competitors like having homologues to more than 75% of human disease genes, having 50% of Drosophila genes are homologues to human genes and most importantly they are genetically amenable. Here, we would like to summarise the extant knowledge about ageing and epigenetic process and the role of Drosophila as an ideal model to study epigenetics in association with ageing process.

The conserved histone chaperone LIN-53 is required for normal lifespan and maintenance of muscle integrity in Caenorhabditis elegans

Whether extension of lifespan provides an extended time without health deteriorations is an important issue for human aging. However, to which degree lifespan and aspects of healthspan regulation might be linked is not well understood. Chromatin factors could be involved in linking both aging aspects, as epigenetic mechanisms bridge regulation of different biological processes. The epigenetic factor LIN‐53 (RBBP4/7) associates with different chromatin‐regulating complexes to safeguard cell identities in Caenorhabditis elegans as well as mammals, and has a role in preventing memory loss and premature aging in humans. We show that LIN‐53 interacts with the nucleosome remodeling and deacetylase (NuRD) complex in C. elegans muscles to ensure functional muscles during postembryonic development and in adults. While mutants for other NuRD members show a normal lifespan, animals lacking LIN‐53 die early because LIN‐53 depletion affects also the histone deacetylase complex Sin3, which is required for a normal lifespan. To determine why lin‐53 and sin‐3 mutants die early, we performed transcriptome and metabolomic analysis revealing that levels of the disaccharide trehalose are significantly decreased in both mutants. As trehalose is required for normal lifespan in C. elegans, lin‐53 and sin‐3 mutants could be rescued by either feeding with trehalose or increasing trehalose levels via the insulin/IGF1 signaling pathway. Overall, our findings suggest that LIN‐53 is required for maintaining lifespan and muscle integrity through discrete chromatin regulatory mechanisms. Since both LIN‐53 and its mammalian homologs safeguard cell identities, it is conceivable that its implication in lifespan regulation is also evolutionarily conserved.

Nuclear Organization in Stress and Aging

The eukaryotic nucleus controls most cellular processes. It is isolated from the cytoplasm by the nuclear envelope, which plays a prominent role in the structural organization of the cell, including nucleocytoplasmic communication, chromatin positioning, and gene expression. Alterations in nuclear composition and function are eminently pronounced upon stress and during premature and physiological aging. These alterations are often accompanied by epigenetic changes in histone modifications. We review, here, the role of nuclear envelope proteins and histone modifiers in the 3-dimensional organization of the genome and the implications for gene expression. In particular, we focus on the nuclear lamins and the chromatin-associated protein BAF, which are linked to Hutchinson–Gilford and Nestor–Guillermo progeria syndromes, respectively. We also discuss alterations in nuclear organization and the epigenetic landscapes during normal aging and various stress conditions, ranging from yeast to humans.

Dysregulation of Neuronal Gαo Signaling by Graphene Oxide in Nematode Caenorhabditis elegans

Exposure to graphene oxide (GO) induced some dysregulated microRNAs (miRNAs), such as the increase in mir-247, in nematode Caenorhabditis elegans. We here further identified goa-1 encoding a Gαo and pkc-1 encoding a serine/threonine protein kinase as the targets of neuronal mir-247 in the regulation of GO toxicity. GO exposure increased the expressions of both GOA-1 and PKC-1. Mutation of goa-1 or pkc-1 induced a susceptibility to GO toxicity, and suppressed the resistance of mir-247 mutant to GO toxicity. GOA-1 and PKC-1 could also act in the neurons to regulate the GO toxicity, and neuronal overexpression of mir-247 could not affect the resistance of nematodes overexpressing neuronal goa-1 or pkc-1 lacking 3'-UTR to GO toxicity. In the neurons, GOA-1 acted upstream of diacylglycerol kinase/DGK-1 and PKC-1 to regulate the GO toxicity. Moreover, DGK-1 and GOA-1 functioned synergistically in the regulation of GO toxicity. Our results highlight the crucial role of neuronal Gαo signaling in response to GO in nematodes.

CFP-1 interacts with HDAC1/2 complexes in C. elegans development

CXXC finger binding protein 1 (CFP-1) is an evolutionarily conserved protein that binds to non-methylated CpG-rich promoters in mammals and Caenorhabditis elegans. This conserved epigenetic regulator is part of the COMPASS complex that contains the H3K4me3 methyltransferase SET1 in mammals and SET-2 in C. elegans. Previous studies have indicated the importance of CFP1 in embryonic stem cell differentiation and cell fate specification. However, neither the function nor the mechanism of action of CFP1 is well understood at the organismal level. Here, we have used cfp-1(tm6369) and set-2(bn129) C. elegans mutants to investigate the function of CFP-1 in gene induction and development. We have characterised C. elegansCOMPASS mutants cfp-1(tm6369) and set-2(bn129) and found that both cfp-1 and set-2 play an important role in the regulation of fertility and development of the organism. Furthermore, we found that both cfp-1 and set-2 are required for H3K4 trimethylation and play a repressive role in the expression of heat shock and salt-inducible genes. Interestingly, we found that cfp-1 but not set-2 genetically interacts with histone deacetylase (HDAC1/2) complexes to regulate fertility, suggesting a function of CFP-1 outside of the COMPASS complex. Additionally, we found that cfp-1 and set-2 independently regulate fertility and development of the organism. Our results suggest that CFP-1 genetically interacts with HDAC1/2 complexes to regulate fertility, independent of its function within the COMPASS complex. We propose that CFP-1 could cooperate with the COMPASS complex and/or HDAC1/2 in a context-dependent manner.

Epigenetic changes during aging and their reprogramming potential

The aging process results in significant epigenetic changes at all levels of chromatin and DNA organization. These include reduced global heterochromatin, nucleosome remodeling and loss, changes in histone marks, global DNA hypomethylation with CpG island hypermethylation, and the relocalization of chromatin modifying factors. Exactly how and why these changes occur is not fully understood, but evidence that these epigenetic changes affect longevity and may cause aging, is growing. Excitingly, new studies show that age-related epigenetic changes can be reversed with interventions such as cyclic expression of the Yamanaka reprogramming factors. This review presents a summary of epigenetic changes that occur in aging, highlights studies indicating that epigenetic changes may contribute to the aging process and outlines the current state of research into interventions to reprogram age-related epigenetic changes.

Emerging topics in C. elegans aging research: Transcriptional regulation, stress response and epigenetics

Key discoveries in aging research have been made possible with the use of model organisms. Caenorhabditis elegans is a short-lived nematode that has become a well-established system to study aging. The practicality and powerful genetic manipulations associated with this metazoan have revolutionized our ability to understand how organisms age. 25 years after the publication of the discovery of the daf-2 gene as a genetic modifier of lifespan, C. elegans remains as relevant as ever in the quest to understand the process of aging. Nematode aging research has proven useful in identifying transcriptional regulators, small molecule signals, cellular mechanisms, epigenetic modifications associated with stress resistance and longevity, and lifespan-extending compounds. Here, we review recent discoveries and selected topics that have emerged in aging research using this incredible little worm.

Chromatin Architectural Changes during Cellular Senescence and Aging

Chromatin 3D structure is highly dynamic and associated with many biological processes, such as cell cycle progression, cellular differentiation, cell fate reprogramming, cancer development, cellular senescence, and aging. Recently, by using chromosome conformation capture technologies, tremendous findings have been reported about the dynamics of genome architecture, their associated proteins, and the underlying mechanisms involved in regulating chromatin spatial organization and gene expression. Cellular senescence and aging, which involve multiple cellular and molecular functional declines, also undergo significant chromatin structural changes, including alternations of heterochromatin and disruption of higher-order chromatin structure. In this review, we summarize recent findings related to genome architecture, factors regulating chromatin spatial organization, and how they change during cellular senescence and aging.

An integrative system biology approach to unravel potential drug candidates for multiple age related disorders

Aging, though an inevitable part of life, is becoming a worldwide social and economic problem. Healthy aging is usually marked by low probability of age related disorders. Good therapeutic approaches are still in need to cure age related disorders. Occurrence of more than one ARD in an individual, expresses the need of discovery of such target proteins, which can affect multiple ARDs. Advanced scientific and medical research technologies throughout last three decades have arrived to the point where lots of key molecular determinants affect human disorders can be examined thoroughly. In this study, we designed and executed an approach to prioritize drugs that may target multiple age related disorders. Our methodology, focused on the analysis of biological pathways and protein protein interaction networks that may contribute to the pharmacology of age related disorders, included various steps such as retrieval and analysis of data, protein-protein interaction network analysis, and statistical and comparative analysis of topological coefficients, pathway, and functional enrichment analysis, and identification of drug-target proteins. We assume that the identified molecular determinants may be prioritized for further screening as novel drug targets to cure multiple ARDs. Based on the analysis, an online tool named as 'ARDnet' has been developed to construct and demonstrate ARD interactions at the level of PPI, ARDs and ARDs protein interaction, ARDs pathway interaction and drug-target interaction. The tool is freely made available at http://genomeinformatics.dtu.ac.in/ARDNet/Index.html.

A Network of Chromatin Factors Is Regulating the Transition to Postembryonic Development in Caenorhabditis elegans

Mi2 proteins are evolutionarily conserved, ATP-dependent chromatin remodelers of the CHD family that play key roles in stem cell differentiation and reprogramming. In Caenorhabditis elegans, the let-418 gene encodes one of the two Mi2 homologs, which is part of at least two chromatin complexes, namely the Nucleosome Remodeling and histone Deacetylase (NuRD) complex and the MEC complex, and functions in larval development, vulval morphogenesis, lifespan regulation, and cell fate determination. To explore the mechanisms involved in the action of LET-418/Mi2, we performed a genome-wide RNA interference (RNAi) screen for suppressors of early larval arrest associated with let-418 mutations. We identified 29 suppressor genes, of which 24 encode chromatin regulators, mostly orthologs of proteins present in transcriptional activator complexes. The remaining five genes vary broadly in their predicted functions. All suppressor genes could suppress multiple aspects of the let-418 phenotype, including developmental arrest and ectopic expression of germline genes in the soma. Analysis of available transcriptomic data and quantitative PCR revealed that LET-418 and the suppressors of early larval arrest are regulating common target genes. These suppressors might represent direct competitors of LET-418 complexes for chromatin regulation of crucial genes involved in the transition to postembryonic development.

SKN-1-independent transcriptional activation of glutathione S-transferase 4 (GST-4) by EGF signaling

In C. elegans research, transcriptional activation of glutathione S-transferase 4 (gst-4) is often used as a read-out for SKN-1 activity. While many heed an assumed non-exclusivity of the GFP reporter signal driven by the gst-4 promoter to SKN-1, this is also often ignored. We here show that gst-4 can also be transcriptionally activated by EOR-1, a transcription factor mediating effects of the epidermal growth factor (EGF) pathway. Along with enhancing exogenous oxidative stress tolerance, EOR-1 inde-pendently of SKN-1 increases gst-4 transcription in response to augmented EGF signaling. Our findings caution researchers within the C. elegans community to always rely on sufficient experimental controls when assaying SKN-1 transcriptional activity with a gst-4_p::gfp reporter, such as SKN-1 loss-of-function mutants and/or additional target genes next to gst-4.

Epigenetics and aging

Over the past decade, a growing number of studies have revealed that progressive changes to epigenetic information accompany aging in both dividing and nondividing cells. Functional studies in model organisms and humans indicate that epigenetic changes have a huge influence on the aging process. These epigenetic changes occur at various levels, including reduced bulk levels of the core histones, altered patterns of histone posttranslational modifications and DNA methylation, replacement of canonical histones with histone variants, and altered noncoding RNA expression, during both organismal aging and replicative senescence. The end result of epigenetic changes during aging is altered local accessibility to the genetic material, leading to aberrant gene expression, reactivation of transposable elements, and genomic instability. Strikingly, certain types of epigenetic information can function in a transgenerational manner to influence the life span of the offspring. Several important conclusions emerge from these studies: rather than being genetically predetermined, our life span is largely epigenetically determined; diet and other environmental influences can influence our life span by changing the epigenetic information; and inhibitors of epigenetic enzymes can influence life span of model organisms. These new findings provide better understanding of the mechanisms involved in aging. Given the reversible nature of epigenetic information, these studies highlight exciting avenues for therapeutic intervention in aging and age-associated diseases, including cancer.

The nucleosome remodeling and deacetylase complex in development and disease

The nucleosome remodeling and deacetylase (NuRD) complex is one of the major chromatin remodeling complexes found in cells. It plays an important role in regulating gene transcription, genome integrity, and cell cycle progression. Through its impact on these basic cellular processes, increasing evidence indicates that alterations in the activity of this macromolecular complex can lead to developmental defects, oncogenesis, and accelerated aging. Recent genetic and biochemical studies have elucidated the mechanisms of NuRD action in modifying the chromatin landscape. These advances have the potential to lead to new therapeutic approaches to birth defects and cancer.

The GATA transcription factor/MTA-1 homolog egr-1 promotes longevity and stress resistance in Caenorhabditis elegans

Aging is associated with a large number of both phenotypic and molecular changes, but for most of these, it is not known whether these changes are detrimental, neutral, or protective. We have identified a conserved Caenorhabditis elegans GATA transcription factor/MTA-1 homolog egr-1 (lin-40) that extends lifespan and promotes resistance to heat and UV stress when overexpressed. Expression of egr-1 increases with age, suggesting that it may promote survival during normal aging. This increase in expression is dependent on the presence of the germline, raising the possibility that egr-1 expression is regulated by signals from the germline. In addition, loss of egr-1 suppresses the long lifespan of insulin receptor daf-2 mutants. The DAF-16 FOXO transcription factor is required for the increased stress resistance of egr-1 overexpression mutants, and egr-1 is necessary for the proper regulation of sod-3 (a reporter for DAF-16 activity). These results indicate that egr-1 acts within the insulin signaling pathway. egr-1 can also activate the expression of its paralog egl-27, another factor known to extend lifespan and increase stress resistance, suggesting that the two genes act in a common program to promote survival. These results identify egr-1 as part of a longevity-promoting circuit that changes with age in a manner that is beneficial for the lifespan of the organism.