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PubMed2026

Epigenetic safety of in vitro maturation in PCOS: genome-wide DNA methylation profiling of cord blood from a randomized controlled trial.

BACKGROUND: In vitro maturation (IVM) provides a safer alternative to conventional in vitro fertilization (IVF) for women with polycystic ovary syndrome (PCOS) by mitigating the risk of ovarian hyperstimulation. However, concerns persist regarding whether IVM perturbs epigenetic reprogramming in the offspring. Current evidence is constrained by candidate-gene approaches or a lack of parental controls. This study aimed to evaluate the genome-wide DNA methylation safety of IVM compared with conventional IVF using a rigorous trio-based design. METHODS: This secondary epigenetic analysis was nested within a randomized controlled trial (RCT) (ClinicalTrials.gov: NCT03463772). We included 10 nuclear families (trios), comprising five IVM-conceived and five IVF-conceived singleton offspring alongside their biological parents. Both groups utilized a uniform freeze-only single-blastocyst transfer strategy to minimize hormonal confounding. Genomic DNA from umbilical cord blood (UCB) and parental peripheral blood was analyzed using reduced representation bisulfite sequencing (RRBS). Genome-wide methylation patterns and differentially methylated regions (DMRs) were subsequently compared between the groups. RESULTS: Clinical characteristics were comparable between the IVM and IVF groups. Genome-wide analyses demonstrated high concordance in UCB methylation patterns, revealing no significant differences in global CpG methylation levels or distributions across key genomic features (promoters, CpG islands, and gene bodies). Only three rare DMRs were identified in UCB (representing ~ 0.0001% of the genome), none of which mapped to imprinted or developmentally critical loci. Furthermore, methylation variability remained consistent between the groups. CONCLUSIONS: Our findings provide robust mechanistic evidence supporting the epigenetic safety of IVM. The remarkable stability of the neonatal methylome confirms that specific IVM conditions do not compromise early developmental programming, thereby endorsing IVM as a safe and viable alternative for women with PCOS. TRIAL REGISTRATION: ClinicalTrials.gov registry, NCT03463772. Registered on March 13, 2018.

Humans↗

PubMed2026

DNA Methylation and Proteomic Profiling of Postmortem Brain Tissue Reveals Epigenetic Dysregulation and Neuroinflammatory in Fragile X-associated Tremor/Ataxia Syndrome (FXTAS).

BACKGROUND: Fragile X-associated Tremor/Ataxia Syndrome (FXTAS) is a late-onset neurodegenerative disorder caused by FMR1 premutation CGG repeat expansions (55-200 repeats). The epigenetic landscape of the FXTAS brain remains uncharacterized. We performed genome-wide DNA methylation profiling of postmortem prefrontal cortex tissue to identify differentially methylated positions (DMPs) and candidate genes, and sought protein-level support for a neuroinflammatory signal. METHODS: DNA methylation was profiled in postmortem prefrontal cortex (Brodmann area 9) from 27 male FXTAS cases and 29 male controls using the Illumina MethylationEPIC array (EPICv1 and EPICv2 platforms), merging 721,802 common probes. Surrogate variable analysis (SVA) controlled for confounders. DMPs were defined by |Δβ| > 0.10 and FDR < 0.05; exploratory Reactome 2024 pathway analysis was performed on the DMP-associated gene list. Targeted proteomic profiling was performed in the same brain region using the Olink (proximity extension assay) Inflammation panel in 9 FXTAS cases and 12 controls, with SVA-adjusted differential abundance analysis, and concordance assessment against a prior mass spectrometry dataset. RESULTS: We identified 108 significant cg-type DMPs mapping to 80 genes (50 hypermethylated, 58 hypomethylated in FXTAS). The strongest signal was CYP2E1 (7 concordant hypomethylated DMPs, mean Δβ = -0.143), an oxidative stress gene also implicated in Parkinson's disease. FTCD, a one-carbon cycle enzyme, carried 5 hypermethylated DMPs (mean Δβ = +0.210). A cluster of DMP-associated genes with established roles in innate immune and NF-κB signaling, TRAF3 (the single most significant DMP among the inflammation genes, hypermethylated), BATF, RCOR1, and MSI2; they pointed toward neuroinflammatory dysregulation. Additional genes included LINGO1 (myelination inhibitor), SYT3 (synaptic vesicle), and SLC39A4 (zinc transporter). Exploratory Reactome enrichment using the DMP-associated gene set nominated themes including neuroinflammation resolution, axonal growth inhibition, zinc homeostasis, and CYP2E1 metabolism at nominal significance (p<0.05); however, the gene-to-pathway mapping rate was low and no pathway survived correction for multiple testing. Olink proteomic analysis independently identified 60 significantly altered inflammation proteins (59 downregulated), including CXCL8, CXCL10, IL6, IL15, IL18, TLR3, IRAK1/4, and complement C1QA, which were directionally concordant with prior mass spectrometry data. CONCLUSIONS: This integrated study reveals a genome-wide epigenetic signature in the FXTAS prefrontal cortex implicating oxidative stress, myelination failure, zinc dysregulation, one-carbon cycle disruption, and most notably a coordinated set of epigenetically altered genes governing innate immune and NF-κB signaling. Convergence of TRAF3 hypermethylation with independent downregulation of TLR3 and NF-κB-pathway proteins at the protein level supports a coherent, cross-platform model of dysregulated neuroinflammatory signaling in FXTAS, identified here through individual gene- and protein-level convergence rather than formal pathway enrichment. FTCD hypermethylation proposes a self-reinforcing epigenetic loop via SAM depletion. These multi-omic findings establish FXTAS as a disorder of pervasive epigenetic reprogramming and nominate candidate genes for future mechanistic and therapeutic investigation.

CYP2E1↗

PubMed2006

Competitive signal discrimination, methylation reprogramming and genomic imprinting.

Genomic imprinting (parent-of-origin-dependent gene regulation) is associated with intra-genomic evolutionary conflict over the optimal pattern of gene expression. Most theoretical models of imprinting focus on the conflict between the maternally and paternally derived alleles at an imprinted locus. Recently, however, more attention has been focused on multi-directional conflicts involving not only the imprinted gene itself, but also the genes that encode the regulatory machinery responsible for establishing and maintaining imprinted gene expression. In this paper, I examine the conflict involved in epigenetic reprogramming of imprinted genes in early mammalian embryonic development. In the earliest phase of development, maternal-store proteins are responsible for most regulatory activity in the embryo. These proteins are under selection to maximize the mother's inclusive fitness, which is not identical to that of either of the sets of genes present in the embryo. Both the maternally and paternally derived genomes in the embryo favor maintenance of the epigenetic modifications established in the female and male germlines, respectively. Maternal-store proteins favor maintenance of some of these modifications, but erasure of others. Here I consider the logical structure of the machinery responsible for these two activities. Methylation maintenance is most effectively performed by AND-linked architectures, which may explain the unusual trafficking behavior of the oocyte-specific DNA methyltransferase, Dnmt1o. By contrast, demethylation is better supported by OR-linked architectures, which may explain the difficulty in identifying the factor(s) responsible for the active demethylation of the paternal genome following fertilization.

Alleles↗

PubMed2025

Epigenetic orchestration of cancer-immune dynamics: mechanisms, technologies, and clinical advancements.

BACKGROUND: Epigenetic dysregulation plays a pivotal role in cancer immune evasion by orchestrating tumour antigen silencing, immune cell dysfunction, and the formation of an immunosuppressive microenvironment. By disrupting successive phases of the cancer-immunity cycle-from antigen presentation to T cell exhaustion-these aberrations facilitate immune escape and tumour progression, highlighting the need for targeted epigenetic intervention. AIM OF REVIEW: This review systematically dissects how epigenetic alterations impair anti-tumour immunity at each stage of the CI cycle. It not only integrates fragmented mechanistic evidence but also emphasizes underexplored crosstalk between specific epigenetic regulators and immune cell types. It further highlights emerging technologies-such as single-cell epigenomics, spatial multi-omics, and CRISPR-based screens-that are driving discovery of novel therapeutic targets and refining patient stratification. Key scientific concepts of review. We discuss how epigenetic interventions, alone or in combination with immunotherapies, can reinvigorate immune responses and overcome resistance to current treatments. A particular focus is given to how integrative high-resolution platforms are mapping immunoepigenetic landscapes, enabling mechanism-informed, precision immunotherapy strategies. By bridging epigenetic regulation with translational immuno-oncology, this review outlines a future where epigenetic reprogramming becomes central to overcoming immune evasion in cancer.

Humans↗

PubMed2006

Stem cell fusion as an ultimate line of defense against xenobiotics.

There are several indications that the potential of stem cells to fuse with somatic cells is extremely high and, what's more exciting, in some instances goes as far as reprogramming and/or rescuing altered cells. It remains unclear, however, how frequent this mechanism is and what patho-physiological role it might play in nature. A plausible hypothesis, discussed in this paper, suggests that stem cell niches might provide a safeguard for the intact genome and epigenome. By fusing with somatic de-differentiated cells, stem cells might consent epigenetic reprogramming and/or genetic recovery of genes which otherwise could drive altered cells to malignancy. If the many sophisticated mechanisms of metabolism, cell repair, programmed cell death and tissue regeneration should fail, stem cells might represent a final attempt to recover dedifferentiated cells to avoid inflowing in cancer. In the current reappraisal of the different mechanisms of defense against xenobiotics, even the incidence of cancer itself is considered an evolving mechanism which, through a kind of programmed death of individuals exhibiting defective mutations, favors advancement of the phenotypes which adapt best. Additionally, with regard to the mechanisms of transmitting somatic mutations, based on stem cells' capacity to migrate and to fuse, here it is speculated that stem cells might be capable of carrying acquired somatic mutations from peripheral tissues to the gonads, and transmit that information into the germinal line. If appropriately demonstrated, these mechanisms might delineate a novel therapeutic area to be explored. The use of stem cells to reprogram/recover irreversibly damaged cells or to transmit beneficial mutations might be a valuable therapeutic approach in the future.

Animals↗

PubMed2002

The novel BORIS + CTCF gene family is uniquely involved in the epigenetics of normal biology and cancer.

CTCF is a ubiquitous 11 zinc finger (ZF) protein with highly versatile functions: in addition to transcriptional silencing or activating in a context-dependent fashion, it organizes epigenetically controlled chromatin insulators that regulate imprinted genes in soma. Recently, we have identified a CTCF paralogue, termed BORIS for Brother of the Regulator of Imprinted Sites, that is expressed only in the testis. BORIS has the same exons encoding the 11 ZF domain as mammalian CTCF genes, and hence interacts with similar cis elements, but encodes amino and carboxy termini distinct from those in CTCF. Normally, CTCF and BORIS are expressed in a mutually exclusive pattern that correlates with re-setting of methylation marks during male germ cell differentiation. The antagonistic features of these two gene siblings are underscored by showing that while CTCF overexpression blocks cell proliferation, expression of BORIS in normally BORIS-negative cells promotes cell growth which can lead to transformation. The suggestion that BORIS directs epigenetic reprogramming at CTCF target sites impinges on the observations that human BORIS is not only abnormally activated in a wide range of human cancers, but also maps to the cancer-associated amplification region at 20q13. The sibling rivalry occasioned by aberrant expression of BORIS in cancer may interfere with normal functions of CTCF including growth suppression, and contribute to epigenetic dysregulation which is a common feature in human cancer.

Animals↗

PubMed2005

Animal cloning: problems and prospects.

An efficient animal cloning technology would provide many new opportunities for livestock agriculture, human medicine, and animal conservation. Nuclear cloning involves the production of animals that are genetically identical to the donor cells used in a technique known as nuclear transfer (NT). However, at present it is an inefficient process: in cattle, only around 6% of the embryos transferred to the reproductive tracts of recipient cows result in healthy, longterm surviving clones. Of concern are the high losses throughout gestation, during birth and in the post-natal period through to adulthood. Many of the pregnancy losses relate to failure of the placenta to develop and function correctly. Placental dysfunction may also have an adverse influence on postnatal health. These anomalies are probably due to incorrect epigenetic reprogramming of the donor genome following NT, leading to inappropriate patterns of gene expression during the development of clones. Whilst some physiological tests on surviving clones suggest normality, other reports indicate a variety of post-natal clone-associated abnormalities. This variability in outcome may reflect species-specific and/or cloning methodological differences. Importantly, to date it appears that these clone-associated phenotypes are not transmitted to offspring following sexual reproduction. This indicates that they represent epigenetic errors, rather than genetic errors, which are corrected during gametogenesis. Whilst this needs confirmation at the molecular level, it provides initial confidence in the first application of NT in agriculture, namely, the production of small numbers of cloned sires from genetically elite bulls, for natural mating, to effectively disseminate genetic gain. In addition to the animal welfare concerns with the technology, the underlying health of the animals and the consequential effect on food safety are critical aspects that require investigation to gain regulatory and consumer acceptance. Future improvements in animal cloning will largely arise from a greater understanding of the molecular mechanisms of reprogramming.

Animal Welfare↗

PubMed2026

Metabolic convergence of diabetes and prostate cancer: from dysglycemia to tumor microenvironment reprogramming.

The relationship between diabetes mellitus and prostate cancer (PC) represents one of the most intriguing paradoxes in cancer epidemiology, with diabetic individuals exhibiting a reduced incidence of PC yet poorer prognosis following diagnosis. This apparent contradiction underscores the need for an integrated understanding of how systemic metabolic dysfunction influences prostate carcinogenesis and disease progression. The present review critically synthesizes contemporary epidemiological, mechanistic, and translational evidence to establish metabolic convergence as a unifying framework linking diabetes-associated metabolic abnormalities with PC biology. Current evidence indicates that chronic dysglycemia, hyperinsulinemia, insulin resistance, and endocrine perturbations orchestrate interconnected intracellular signaling networks involving PI3K-AKT-mTOR, AMPK, AGE-RAGE signaling, oxidative stress, mitochondrial dysfunction, and epigenetic reprogramming, collectively driving metabolic adaptation and tumor evolution. Beyond tumor-intrinsic mechanisms, diabetes profoundly remodels the prostate tumor microenvironment through alterations in stromal metabolism, cancer-associated fibroblast activation, adipocyte-tumor crosstalk, extracellular matrix (ECM) remodeling, hypoxic adaptation, and vascular dysfunction, while simultaneously promoting immunometabolic reprogramming characterized by macrophage polarization, T-cell dysfunction, immune checkpoint activation, and immune evasion. The review further examines the bidirectional interactions between antidiabetic therapies and PC treatment, critically evaluating the translational potential of metformin and emerging glucose-lowering agents within the context of precision metabolic therapeutics. Finally, future directions encompassing biomarker-guided patient stratification, longitudinal metabolic profiling, multi-omics integration, artificial intelligence, and clinically relevant mechanistic validation are discussed as essential components of next-generation precision oncology. Collectively, this review reframes diabetes as an active metabolic determinant of PC rather than a coincidental comorbidity and highlights metabolism-centered precision strategies as promising avenues for improving risk stratification, therapeutic decision-making, and clinical outcomes in diabetes-associated PC.

Humans↗

PubMed2004

Methylation reprogramming and chromosomal aneuploidy in in vivo fertilized and cloned rabbit preimplantation embryos.

Active demethylation of the paternal genome but not of the maternal genome occurs in fertilized mouse, rat, pig, and bovine zygotes. To study whether this early demethylation wave is important for embryonic development, we have analyzed the global methylation patterns of both in vivo-fertilized and cloned rabbit embryos. Anti-5-methylcytosine immunofluorescence of in vivo-fertilized rabbit embryos revealed that the equally high methylation levels of the paternal and maternal genomes are largely maintained from the zygote up to the 16-cell stage. The lack of detectable methylation changes in rabbit preimplantation embryos suggests that genome-wide demethylation is not an obligatory requirement for epigenetic reprogramming. The methylation patterns of embryos derived from fibroblast and cumulus cell nuclear transfer were similar to those of in vivo-fertilized rabbit embryos. Fluorescence in situ hybridization with chromosome-specific BACs demonstrated significantly increased chromosomal aneuploidy rates in cumulus cell nuclear transfer rabbit embryos and embryos derived from nuclear transfer of rabbit fibroblasts into bovine oocytes compared with in vivo-fertilized rabbit embryos. The incidence of chromosomal abnormalities was correlated with subsequent developmental failure. We propose that postzygotic mitotic errors are one important explanation of why mammalian cloning often fails.

Aneuploidy↗

PubMed2003

Growth restricted in vitro culture conditions alter the imprinted gene expression patterns of mouse embryonic stem cells.

Embryonic stem (ES) cell-derived clones and chimeras are often associated with growth abnormalities during fetal development, leading to the production of over/under-weight offspring that show elevated neonatal mortality and morbidity. Due to the role played by imprinted genes in controlling fetal growth, much of the blame is pointed at improper epigenetic reprogramming of cells used in the procedures. We have analyzed the expression pattern of two growth regulatory imprinted genes, namely insulin like growth factor II (Igf2) and H19, in mouse ES cells cultured under growth restricted conditions and after in vitro aging. Culture of cells with serum-depleted media (starvation) and at high cell density (confluence) increased the expression of both imprinted genes and led to aberrant methylation profiles of differentially methylated regions in key regulatory sites of Igf2 and H19. These findings confirm that growth constrained cultures of ES cells are associated with alterations to methylation of the regulatory domains and the expression patterns of imprinted genes, suggesting a possible role of epigenetic factors in the loss of developmental potential.

Animals↗

PubMed2006

Gene expression dynamics during germline specification in mice identified by quantitative single-cell gene expression profiling.

Germ cell fate in mice is induced in proximal epiblast cells at Embryonic Day (E) 6.5 by signaling molecules. Prdm1(also known as Blimp1)-positive lineage-restricted precursors of primordial germ cells (PGCs) initiate the formation of a cluster that differentiates into Dppa3 (also known as stella)-positive PGCs from around E7.0 onwards in the extra-embryonic mesoderm. Around E7.5, these PGCs begin migrating towards the definitive endoderm, with concomitant extensive epigenetic reprogramming. To gain a more precise insight into the mechanism of PGC specification and its subsequent development, we exploited quantitative, single-cell, gene expression profiling to explore gene expression dynamics during the 36 h of PGC differentiation from E6.75 to E8.25, in comparison with the corresponding profiles of somatic neighbors. This analysis revealed that the transitions from Prdm1-positive PGC precursors to Dppa3-positive PGCs and to more advanced migrating PGCs involve a highly dynamic, stage-dependent transcriptional orchestration that begins with the regaining of the pluripotency-associated gene network, followed by stepwise activation of PGC-specific genes, differential repression of the somatic mesodermal program, as well as potential modulations of signal transduction capacities and unique control of epigenetic regulators. The information presented here regarding the cascade of events involved in PGC development should serve as a basis for detailed functional analyses of the gene products associated with this process, as well as for appropriate reconstitution of PGCs and their descendant cells in culture.

Animals↗

PubMed2001

Conservation of methylation reprogramming in mammalian development: aberrant reprogramming in cloned embryos.

Mouse embryos undergo genome-wide methylation reprogramming by demethylation in early preimplantation development, followed by remethylation thereafter. Here we show that genome-wide reprogramming is conserved in several mammalian species and ask whether it also occurs in embryos cloned with the use of highly methylated somatic donor nuclei. Normal bovine, rat, and pig zygotes showed a demethylated paternal genome, suggesting active demethylation. In bovine embryos methylation was further reduced during cleavage up to the eight-cell stage, and this reduction in methylation was followed by de novo methylation by the 16-cell stage. In cloned one-cell embryos there was a reduction in methylation consistent with active demethylation, but no further demethylation occurred subsequently. Instead, de novo methylation and nuclear reorganization of methylation patterns resembling those of differentiated cells occurred precociously in many cloned embryos. Cloned, but not normal, morulae had highly methylated nuclei in all blastomeres that resembled those of the fibroblast donor cells. Our study shows that epigenetic reprogramming occurs aberrantly in most cloned embryos; incomplete reprogramming may contribute to the low efficiency of cloning.

Animals↗

PubMed2026

How the microbiome shapes epigenetic trained memory in neuroinflammation: Implications for neurodegenerative diseases.

Neurodegenerative diseases are increasingly recognized as disorders involving immune dysregulation. However, the mechanisms underlying this dysfunction remain poorly characterized. Trained immunity has recently emerged as a potential contributor to immune dysregulation, particularly in neuroinflammation and neurodegenerative diseases, where trained immunity is the epigenetic reprogramming of innate immune responses following an initial inflammatory stimulus, which increases responses to subsequent exposures. In parallel, although the brain has traditionally been viewed as an immune-privileged organ, growing evidence indicates that peripheral immune activity exerts significant influence on neuroinflammation in the brain. A major driver of peripheral immunity is the microbiome. Therefore, this perspective aims to present a conceptual framework for a relationship between the microbiome, trained immunity, and neurodegenerative diseases. We first summarize evidence of trained immunity in the brain and its role in neurodegeneration. Next, we highlight the role of the microbiome in peripheral immune modulation and in trained immunity. Finally, we propose potential mechanisms through which the microbiome may induce or modulate trained immunity in the brain. These include: 1) immunogenic microbial metabolites that cross the blood-brain barrier and alter host cell epigenetics; 2) migration of peripherally trained myeloid cells into the brain; 3) viral infection-induced trained immunity that may predispose to neurodegeneration. Together, this perspective suggests that microbiome-induced trained immunity offers a novel mechanism linking peripheral immune regulation with neuroinflammation and neurodegeneration with implications for therapeutic targeting of epigenetic modification as a molecular prevention strategy for progression of neurodegeneration.

Humans↗

PubMed2006

A unique configuration of genome-wide DNA methylation patterns in the testis.

In the mammalian lifecycle, the two periods of genome-wide epigenetic reprogramming are in the early embryo, when somatic patterns are set, and during germ cell development. Although some differences between the reprogrammed states of somatic and germ cells have been reported, overall patterns of genomic methylation are considered to be similar. Using restriction landmark genomic scanning to examine approximately 2,600 loci distributed randomly throughout the genome, we find that the methylation status of testicular DNA is highly distinct, displaying eightfold the number of hypomethylated loci relative to somatic tissues. Identification and analysis of >300 loci show that these regions are generally located within nonrepetitive sequences that are away from CpG islands and 5' regions of genes. We show that a contributing factor for these differences is that the methylation state of non-CpG-island DNA is correlated with the regional level of GC content within chromosomes and that this relationship is inverted between the testis and somatic tissues. We also show that in Dnmt3L-deficient mice, which exhibit infertility associated with abnormal chromosomal structures in germ cells, this unique testicular DNA methylation pattern is not established. These special properties of testicular DNA point to a broad, distinct epigenetic state that may be involved in maintaining a unique chromosomal structure in male germ cells.

Animals↗

PubMed2026

Epigenetic regulation of fatty acid chain elongation in MAFLD and its implications in the liver-brain axis dysfunction.

Lipid metabolism plays a crucial role in cellular health and physiology by acting as an energy storehouse, cell membrane component, brain development and signaling molecules. Crucial steps to metabolize dietary fat take place within the hepatic tissue. Any abnormalities in the hepatic fatty metabolic pathways cause abnormal accumulation of lipid inside the liver, causing MAFLD, ranging from simple steatosis to more complex steatohepatitis and fibrosis. During high-fat-diet-induced hepatic inflammation, systemic proinflammatory cytokines disrupt the blood-brain barrier, resulting in neuroinflammation, cognitive impairment, brain damage and even neurodegeneration. Further, during this altered metabolic scenario, circulating metabolites pass through the impaired BBR and deregulate the epigenetic landscape of the central nervous system. Thus, it becomes crucial to understand the epi-metabolic crosstalk between two crucial organs of our body: the liver and the brain. Here in this chapter, we demonstrate the approach that we are using in our laboratory to study the epigenetic reprogramming in the context of metabolic gene expression in the liver, which is the causal for life style disorders like MAFLD. Remarkably, we intend to understand how liver dysfunction can have an implication in the brain function. Here, we discuss the concept of developing a diet-induced steatosis and steatohepatitis mouse model to understand the disease progression and its interconnection with brain physiology. Further, we also demonstrate 2D and 3D cell culture models to study the liver-brain cross-talk in greater molecular detail. Collectively, these approaches can provide a template for studying the role of epi-metabolic cross-talk in liver-guided brain dysfunction upon MAFLD.

Animals↗

PubMed2004

Effect of limited DNA methylation reprogramming in the normal sheep embryo on somatic cell nuclear transfer.

Active demethylation of cytosine residues in the sperm genome before forming a functional zygotic nucleus is thought to be an important function of the oocyte cytoplasm for subsequent embryonic development in the mouse. Conversely, this event does not occur in the sheep or rabbit zygote and occurs only partially in the cow. The aim of this study was to investigate the effect of limited methylation reprogramming in the normal sheep embryo on reprogramming somatic nuclei. Sheep fibroblast somatic nuclei were partially demethylated after electrofusion with recipient sheep oocytes and undergo a stepwise passive loss of DNA methylation during early development, as determined by 5-methylcytosine immunostaining on interphase embryonic nuclei. A similar decrease takes place with in vivo-derived sheep embryos up to the eight-cell stage, although nuclear transfer embryos exhibit a consistently higher level of methylation at each stage. Between the eight-cell and blastocyst stages, DNA methylation levels in nuclear transfer embryos are comparable with those derived in vivo, but the distribution of methylated DNA is abnormal in a high proportion. By correlating DNA methylation with developmental potential at individual stages, our results suggest that somatic nuclei that do not undergo rapid reorganization of their DNA before the first mitosis fail to develop within two to three cell cycles and that the observed methylation defects in early cleavage stages more likely occur as a direct consequence of failed nuclear reorganization than in failed demethylation capacity. However, because only embryos with reorganized chromatin appear to survive the 16-cell and morula stages, failure to demethylate the trophectoderm cells of the blastocyst is likely to directly impact on developmental potential by altering programmed patterns of gene expression in extra-embryonic tissues. Thus, both remodeling of DNA and epigenetic reprogramming appear critical for development of both fertilized and nuclear transfer embryos.

Animals↗

PubMed2005

Conditional expression of the CTCF-paralogous transcriptional factor BORIS in normal cells results in demethylation and derepression of MAGE-A1 and reactivation of other cancer-testis genes.

Brother of the Regulator of Imprinted Sites (BORIS) is a mammalian CTCF paralog with the same central 11Zn fingers (11ZF) that mediate specific interactions with varying approximately 50-bp target sites. Regulated in vivo occupancy of such sites may yield structurally and functionally distinct CTCF/DNA complexes involved in various aspects of gene regulation, including epigenetic control of gene imprinting and X chromosome inactivation. The latter functions are mediated by meCpG-sensitive 11ZF binding. Because CTCF is normally present in all somatic cells, whereas BORIS is active only in CTCF- and 5-methylcytosine-deficient adult male germ cells, switching DNA occupancy from CTCF to BORIS was suggested to regulate site specificity and timing of epigenetic reprogramming. In addition to 11ZF-binding paternal imprinting control regions, cancer-testis gene promoters also undergo remethylation during CTCF/BORIS switching in germ cells. Only promoters of cancer testis genes are normally silenced in all somatic cells but activated during spermatogenesis when demethylated in BORIS-positive germ cells and are found aberrantly derepressed in various tumors. We show here that BORIS is also expressed in multiple cancers and is thus itself a cancer-testis gene and that conditional expression of BORIS in normal fibroblasts activates cancer-testis genes selectively. We tested if replacement of CTCF by BORIS on regulatory DNA occurs in vivo on activation of a prototype cancer-testis gene, MAGE-A1. Transition from a hypermethylated/silenced to a hypomethylated/activated status induced in normal cells by 5-aza-2'-deoxycytidine (5-azadC) was mimicked by conditional input of BORIS and is associated with complete switching from CTCF to BORIS occupancy at a single 11ZF target. This site manifested a novel type of CTCF/BORIS 11ZF binding insensitive to CpG methylation. Whereas 5-azadC induction of BORIS takes only few hours, derepression of MAGE-A1 occurred 1 to 2 days later, suggesting that BORIS mediates cancer-testis gene activation by 5-azadC. Indeed, infection of normal fibroblasts with anti-BORIS short hairpin RNA retroviruses before treatment with 5-azadC blocked reactivation of MAGE-A1. We suggest that BORIS is likely tethering epigenetic machinery to a novel class of CTCF/BORIS 11ZF target sequences that mediate induction of cancer-testis genes.

Animals↗

PubMed1996

Role of programmed (apoptotic) cell death during the progression and therapy for prostate cancer.

Cells possess within their epigenetic repertoire the ability to undergo an active process of cellular suicide termed programmed (or apoptotic) cell death. This programmed cell death process involves an epigenetic reprogramming of the cell that results in an energy-dependent cascade of biochemical and morphologic changes (also termed apoptosis) within the cell, resulting in its death and elimination. Although the final steps (i.e., DNA and cellular fragmentation) are common to cells undergoing programmed cell death, the activation of this death process is initiated either by sufficient injury to the cell induced by various exogenous damaging agents (e.g., radiation, chemicals, viruses) or by changes in the levels of a series of endogenous signals (e.g., hormones and growth/survival factors). Within the prostate, androgens are capable of both stimulating proliferation as well as inhibiting the rate of the glandular epithelial cell death. Androgen withdrawal triggers the programmed cell death pathway in both normal prostate glandular epithelia and androgen-dependent prostate cancer cells. Androgen-independent prostate cancer cells do not initiate the programmed cell death pathway upon androgen ablation; however, they do retain the cellular machinery necessary to activate the programmed cell death cascade when sufficiently damaged by exogenous agents. In the normal prostate epithelium, cell proliferation is balanced by a equal rate of programmed cell death, such that neither involution nor overgrowth normal occurs. In prostatic cancer, however, this balance is lost, such that there is greater proliferation than death producing continuous net growth. Thus, an imbalance in programmed cell death must occur during prostatic cancer progression. The goal of effective therapy for prostatic cancer, therefore, is to correct this imbalance. Unfortunately, this has not been achieved and metastatic prostatic cancer is still a lethal disease for which no curative therapy is currently available. In order to develop such effective therapy, an understanding of the programmed death pathway, and what controls it, is critical. Thus, a review of the present state of knowledge concerning programmed cell death of normal and malignant prostatic cells will be presented.

Androgens↗