Alterations In DNA Sequence Research Articles

Molecular genetic analysis and structure model of a rare B(A)02 subgroup of the ABO blood group system

BackgroundSerological analysis of ABO blood group has been widely applied in transfusion medicine. However, ABO subgroups with different expression of blood group antigens sometimes cannot be determined by serological methods. Therefore, genotyping is useful to understand the variant ABO phenotypes. Material and MethodsExon 6 to exon 7 and adjacent introns of the ABO gene from a donor with ABO typing discrepancy were amplified and sequenced. Cloning sequencing was also performed to identify the allele. To explore the effect of mutation, three dimensional model of mutant p.Pro234Ala was built and optimized. ResultsThe variant B (c. 700C > G) allele expressed an AweakB phenotype with anti-A in his serum with a ABO*B(A)02/O02 heterozygote genotype. Cloning sequencing confirmed that the c.700C > G single nucleotide polymorphism was associated with a B101 allele. Three dimensional molecular modeling suggested that p.Pro234Ala might affect the conformation of His233, Met266 and Ala268, which were known as critical residues for donor recognition. ConclusionABO genotyping is needed for correct identification subgroups to improve accuracy evaluation of blood typing and increase the safety of blood transfusion. Alteration of DNA sequence in the ABO gene resulted in amino acid substitutions and led to a weak or missing expression of ABO antigens.

Cardiovascular risk prevention in children

Cardiovascular disease (CVD) is the major cause of mortality in industrialized countries. Atherosclerosis is characterized by a long lag time between onset and clinical manifestations. There is evidence that CVD initiate before birth by developmental changes in utero. Genetic and environmental factors may interact in specific periods of life (prenatal, perinatal, early childhood), giving rise to altered developmental plasticity and epigenetic modifications with abnormal phenotypic expression of genetic information without altering DNA sequence. Nutritional imbalances and other environmental clues may cause intrauterine growth delay, decreased gestational age, low birth weight and postnatal catch-up growth. Fetal exposure to maternal hypercholesterolemia has been associated with increased risk and progression of atherosclerosis. Oxidative stress seems to play a major role in the atherosclerotic process by activating both platelets and monocytes forming proinflammatory and proaterogenic substances, resulting in endothelial dysfunction, decreased flow-mediated dilation, and increased carotid intima-media thickness [1,2]. CVD primary prevention should be implemented early. High risk, apparently healthy [3] subjects should be identified , and treated early by healthy eating, physical activity encouragement, healthy lifestyle, the possible addition of nutraceuticals [4] and adding drugs if risk profile is not decreased. Restoration of endothelial function in the reversible phase of atherosclerosis is an essential step. Epigenetics might provide novel and early markers to identify those at risk, thereby developing innovative therapies.

Epigenetic memory in plants.

Epigenetics refers to heritable changes in patterns of gene expression that occur without alterations in DNA sequence. The epigenetic mechanisms involve covalent modifications of DNA and histones, which affect transcriptional activity of chromatin. Since chromatin states can be propagated through mitotic and meiotic divisions, epigenetic mechanisms are thought to provide heritable 'cellular memory'. Here, we review selected examples of epigenetic memory in plants and briefly discuss underlying mechanisms.

Epigenetic Modulation of Myocardial Angiogenic Balance: An Emerging Therapeutic Perspective for Adult Failing Heart

The term "Epigenetics" refers to chromatin-based pathways involved in the regulation of gene expression without altering DNA sequence. Suppression of angiogenesis may be related to cardiac dysfunction following alterations in capillary microvasculature. An understanding of the relationship between angiogenesis and cardiac remodeling remains the major limitation in order to address the weak self-renewal ability of the adult failing heart. In physiological conditions, genes responsible for sustaining the angiogenic ability of the mature endothelial cells can be categorized into pro- and anti-angiogenic genes. The balanced expression of angiogenic genes maintains a state of equilibrium in capillary density of the adult myocardium. In the context of post-ischemic myocardial dysfunction, transcriptional and posttranscriptional modifications of the gene pool are involved in alterations of angiogenic balance in capillary microvasculature, angiogenesis, myocardial perfusion/contractility match and contractile function. The regulation of angiogenic gene expression by different epigenetic modifications may induce the formation of new vessels from coronary mature endothelial cells rather than endothelial progenitor cells. The role of proangiogenic epigenetic activators is emerging as a new actor in the modulation of the angiogenic balance of failing heart. In fact, the development of an ideal method to promote myocardial revascularization, while attenuating cardiac remodeling, is still a challenging issue. The present review will examine emerging studies on the epigenetic mechanisms involved in the regulation of function and angiogenic ability of mature endothelial cells residing in the adult myocardium.

Precision genome engineering and agriculture: opportunities and regulatory challenges.

Plant agriculture is poised at a technological inflection point. Recent advances in genome engineering make it possible to precisely alter DNA sequences in living cells, providing unprecedented control over a plant's genetic material. Potential future crops derived through genome engineering include those that better withstand pests, that have enhanced nutritional value, and that are able to grow on marginal lands. In many instances, crops with such traits will be created by altering only a few nucleotides among the billions that comprise plant genomes. As such, and with the appropriate regulatory structures in place, crops created through genome engineering might prove to be more acceptable to the public than plants that carry foreign DNA in their genomes. Public perception and the performance of the engineered crop varieties will determine the extent to which this powerful technology contributes towards securing the world's food supply.

MethylSig: a whole genome DNA methylation analysis pipeline

DNA methylation plays critical roles in gene regulation and cellular specification without altering DNA sequences. The wide application of reduced representation bisulfite sequencing (RRBS) and whole genome bisulfite sequencing (bis-seq) opens the door to study DNA methylation at single CpG site resolution. One challenging question is how best to test for significant methylation differences between groups of biological samples in order to minimize false positive findings. We present a statistical analysis package, methylSig, to analyse genome-wide methylation differences between samples from different treatments or disease groups. MethylSig takes into account both read coverage and biological variation by utilizing a beta-binomial approach across biological samples for a CpG site or region, and identifies relevant differences in CpG methylation. It can also incorporate local information to improve group methylation level and/or variance estimation for experiments with small sample size. A permutation study based on data from enhanced RRBS samples shows that methylSig maintains a well-calibrated type-I error when the number of samples is three or more per group. Our simulations show that methylSig has higher sensitivity compared with several alternative methods. The use of methylSig is illustrated with a comparison of different subtypes of acute leukemia and normal bone marrow samples. methylSig is available as an R package at http://sartorlab.ccmb.med.umich.edu/software. Supplementary data are available at Bioinformatics online.

Characterising the atypical 5'-CG DNA sequence specificity of 9-aminoacridine carboxamide Pt complexes.

In this study, the DNA sequence specificity of four DNA-targeted 9-aminoacridine carboxamide Pt complexes was compared with cisplatin, using two specially constructed plasmid templates. One plasmid contained 5'-CG and 5'-GA insert sequences while the other plasmid contained a G-rich transferrin receptor gene promoter insert sequence. The damage profiles of each compound on the different DNA templates were quantified via a polymerase stop assay with fluorescently labelled primers and capillary electrophoresis. With the plasmid that contained 5'-CG and 5'-GA dinucleotides, the four 9-aminoacridine carboxamide Pt complexes produced distinctly different damage profiles as compared with cisplatin. These 9-aminoacridine complexes had greatly increased levels of DNA damage at CG and GA dinucleotides as compared with cisplatin. It was shown that the presence of a CG or GA dinucleotide was sufficient to reveal the altered DNA sequence selectivity of the 9-aminoacridine carboxamide Pt analogues. The DNA sequence specificity of the Pt complexes was also found to be similarly altered utilising the transferrin receptor DNA sequence.

DNA Promoter Methylation-dependent Transcription of the Double C2-like Domain β (DOC2B) Gene Regulates Tumor Growth in Human Cervical Cancer

Double C2-like domain β (DOC2B) gene encodes for a calcium-binding protein, which is involved in neurotransmitter release, sorting, and exocytosis. We have identified the promoter region of the DOC2B gene as hypermethylated in pre-malignant, malignant cervical tissues, and cervical cancer cell lines by methylation-sensitive dimethyl sulfoxide-polymerase chain reaction and bisulfite genome sequencing; whereas, it was unmethylated in normal cervical tissues (p < 0.05). The promoter hypermethylation was inversely associated with mRNA expression in SiHa, CaSki, and HeLa cells and treatment with demethylating agent 5-aza-2-deoxycytidine restored DOC2B expression. The region -630 to +25 bp of the DOC2B gene showed robust promoter activity by a luciferase reporter assay and was inhibited by in vitro artificial methylation with Sss1 methylase prior to transient transfections. Overexpression of the DOC2B gene in SiHa cells when compared with controls showed significantly reduced colony formation, cell proliferation, induced cell cycle arrest, and repressed cell migration and invasion (p < 0.05). Ectopic expression of DOC2B resulted in anoikis-mediated cell death and repressed tumor growth in a nude mice xenograft model (p < 0.05). DOC2B expressing cells showed a significant increase in intracellular calcium level (p < 0.05), impaired AKT1 and ERK1/2 signaling, and induced actin cytoskeleton remodeling. Our results show that promoter hypermethylation and silencing of the DOC2B gene is an early and frequent event during cervical carcinogenesis and whose reduced expression due to DNA promoter methylation may lead to selective cervical tumor growth.

Targeting Epigenetics in Drug Discovery

This Special Issue of ChemMedChem on Epigenetics and Drug Discovery brings together a diverse group of papers on a range of topics from bromodomain inhibitors and long noncoding RNAs to classic agents targeting histone deacetylases (HDACs) and less typical HDAC inhibitors, such as the chimeric compounds designed by Greg Thatcher et al. and featured on the Front Cover of the issue that both target HDACs and act as selective estrogen receptor modulators (SERMs).

Unhealthy Nutrigenomic Diets Accelerate NAFLD and Adiposity in Global communities

The understanding of genetic factors involved in the risk for obesity has identified genes that are closely linked to obesity related diseases. A single gene effect versus multiple genes effect may indicate either the interaction unique to various environments that regulate abnormal molecular or cellular events responsible for obesity with several hypotheses proposed in relation to the development of obesity. The understanding of the development of adipogenesis has been the focus of the global community with obesity genetics, epigenetic regulatory mechanisms and transcription factors important to the world-wide obesity epidemic with increased risk for adiposity. The search for specific genes that are sensitive to nutritional regulation, oxidative stress, inflammation, endocrine disease, lipid/ glucose metabolism, insulin resistance and Alzheimer’s disease has been the focus of the current obesity epidemic in various developed countries. Epigenetics is now considered as an important mechanism for the development of obesity and can result from changes in cellular chromatin structure without alterations in DNA sequence, including DNA methylation, histone modifications and chromatin remodelling. Epigenetic modifications induced by unhealthy diets and the environment effect nuclear/mitochondria interactions and implicate nuclear receptors such as Sirt 1 as a single gene effect with interactions with microRNA and transcription factors such as p53 that regulate cellular and immune events with effects on cellular lipid metabolism and energy expenditure that induce senescence with poor DNA repair. Epigenetic modifications in various communities are now closely involved in NAFLD associated with excess transfer of fat to the adipose tissue and the induction of obesity in developed countries. The failure of various anti-obese drugs has encouraged the use of nutrigenomic diets that reverse senescence and assist in the early nutritional intervention that reverses NAFLD with reduced adiposity.

Epigenetic regulation of double c2 like domain beta (Doc2b) in cervical cancer.

Associations of genetic changes and aneuploidy with tumor growth are traditionally attributed to alterations in DNA sequence manifested as mutations, deletions and amplifications. Inactive tumor suppressor genes could serve as drivers of tumor progression due to not only altered or lack of protein function but may also contribute to phenotypic changes that may provide distinct growth advantage in a hostile environment in the host. Human variation is also due to epigenetic alterations and heritable change that leads to altered gene expression; the functional consequence of which may contribute to definitive trait. A number of key regulatory genes associated with epigenetic silencing due to DNA methylation in cervical cancer have been reported. Elucidation of differentially methylated genes may identify new targets and further strengthen our understanding of molecular mechanism governing pathogenesis of cervical cancer. Thus, to identify DNA methylation regulated genes in cervical cancer, we have employed DMH based microarray experiments in pre-malignant and malignant cervical sample. Microarray data analysis and validation using bisulfite genomic sequencing lead to the identification of several CpG island as altered during cervical carcinogenesis and showed the potential for early screening of cervical cancer. One of the candidate gene identified was Double C2 like Domain beta (DOC2B), a key calcium regulator protein whose alteration has never been linked to cancer. We provide evidence that DOC2B is depressed in cervical cancer due to promoter hypermethylation and act as a novel tumor suppressor gene by regulating multiple pathways in cervical cancer.

The frequency of genetic rearrangements during carrot (Daucus carota) somatic embryogenesis is dependent on 2,4-D levels and diminished in its absence

For quantification of genetic variations occurring in plant tissue cultures, DNA sequence alterations and replicon- size changes were monitored through subsequent phases of the model carrot tissue culture system, from the 2,4-D-induced proembryiogenic cell cultures to regenerated plantlets, by RAPD and flow cytometry techniques. Banding patterns of random amplified DNA fragments and ploidy-level distributions of cultured cells were significantly different in the presence and in the absence of 2,4-D. In addition, there were marked differences between the cells induced with lower (1.0 mg/l) and higher (2.5 mg/l) doses of 2,4-D. Among those samples that were cultured in the absence of 2,4-D, the epicotyl (C2), hypocotyl control (H1) and the morphologically normal regenerants (IV2) showed identical banding patterns overlapping with the true-to-type seedling controls (N1, N2). In contrast, treatment of starting explants (H2) with 1.0 mg/l 2,4-D resulted in a marked 82% increase in the number of amplified fragments associated with an appearance of cell lines possessing unusual haploid-like and aneuploid-like DNA contents. The induction with 2.5 mg/l 2,4-D resulted in even greater increase in the number of DNA fragments (~100%) amplified from proembryiogenic cell cultures, while it had no further effect on ploidiy-level distributions compared to the treatment with 1.0 mg/l 2,-D. After the withdrawal of the synthetic auxin, banding patterns and ploidy-level distributions were gradually shifted back to the levels of controls resulting in true-to-type regenerants. Conclusions are in short, the combined use of RAPD and flow cytometry can make quantification of genetic variations typical of dedifferentiated plant cells possible. Quantification opens the window for comprehensive evaluation of different methods, treatments and bioactive compounds.

Overexpression of Cancer-Associated Genes via Epigenetic Derepression Mechanisms in Gynecologic Cancer

Like other cancers, most gynecologic cancers are caused by aberrant expression of cancer-related genes. Epigenetics is one of the most important gene expression mechanisms, which contribute to cancer development and progression by regulating cancer-related genes. Since the discovery of differential gene expression patterns in cancer cells when compared with normal cells, extensive efforts have been made to explore the origins of abnormal gene expression in cancer. Epigenetics, the study of inheritable changes in gene expression that do not alter DNA sequence is a key area of this research. DNA methylation and histone modification are well-known epigenetic mechanisms, while microRNAs and alternative splicing have recently been identified as important regulators of epigenetic mechanisms. These mechanisms not only affect specific target gene expression but also regulate the functioning of other epigenetic mechanisms. Moreover, these diverse epigenetic regulations occur simultaneously. Epigenetic regulation of gene expression is extraordinarily complicated and all epigenetic mechanisms to be studied at once to determine the exact gene regulation mechanisms. Traditionally, the contribution of epigenetics to cancer is thought to be mediated through the inactivation of tumor suppressor genes expression. But recently, it is arising that some oncogenes or cancer-promoting genes (CPGs) are overexpressed in diverse type of cancers through epigenetic derepression mechanism, such as DNA and histone demethylation. Epigenetic derepression arises from diverse epigenetic changes, and all of these mechanisms actively interact with each other to increase oncogenes or CPGs expression in cancer cell. Oncogenes or CPGs overexpressed through epigenetic derepression can initiate cancer development, and accumulation of these abnormal epigenetic changes makes cancer more aggressive and treatment resistance. This review discusses epigenetic mechanisms involved in the overexpression of oncogenes or CPGs via epigenetic derepression in gynecologic cancers. Therefore, improved understanding of these epigenetic mechanisms will provide new targets for gynecologic cancer treatment.

Tumour suppressor gene and protein TP53/P53 in normal endometrium and endometrial carcinoma

Endometrial carcinoma (ECa) is the most common neoplasia of the female genital system. There are two basic types of ECa, endometrioid (estrogen related, indolent) and non-endometrioid (estrogen unrelated, aggressive). The tp53 is a tumour suppressor gene (17pl3) encoding a DNA-binding phosphoprotein P53, 53kDa, a transcription factor that mediates the cell's response to various kinds of genotoxic stress by preventing cell division and/or inducing DNA excise repair or apoptosis. Tp53 alterations results in an aberrant P53 with a longer half-life that accumulates in the cell. A total of 40 archived formalin-fixed and paraffin-embedded human biopsy tissue specimens with normal proliferative endometrium, endometrioid grade G1 and G3 and serous (SC) subtype of ECa were evaluated by immunohistochemistry for P53 expression/accumulation in nuclei of endometrial-epithelial cells; and by molecular biology methods for the exons 5-8 tp53 DNA sequence alterations. The expression/accumulation of tp53/P53 was related only to aggressive (mainly SC) types of ECa. Tp53 mutations (substitutions) were detected in SC only. There is no expression/accumulation of tp53/P53 in normal endometrium. The tp53/P53 expression/accumulation and tp53 mutations presence are associated with aggressive type of ECa. Evaluation of tp53/P53 in ECa could be a relevant component useful in research and clinical practice.

Site-Specific, Insertional Inactivation of incA in Chlamydia trachomatis Using a Group II Intron

Chlamydia trachomatis is an obligate, intracellular bacterial pathogen that has until more recently remained recalcitrant to genetic manipulation. However, the field still remains hindered by the absence of tools to create selectable, targeted chromosomal mutations. Previous work with mobile group II introns demonstrated that they can be retargeted by altering DNA sequences within the intron’s substrate recognition region to create site-specific gene insertions. This platform (marketed as TargeTron™, Sigma) has been successfully employed in a variety of bacteria. We subsequently modified TargeTron™ for use in C. trachomatis and as proof of principle used our system to insertionally inactivate incA, a chromosomal gene encoding a protein required for homotypic fusion of chlamydial inclusions. C. trachomatis incA::GII(bla) mutants were selected with ampicillin and plaque purified clones were then isolated for genotypic and phenotypic analysis. PCR, Southern blotting, and DNA sequencing verified proper GII(bla) insertion, while continuous passaging in the absence of selection demonstrated that the insertion was stable. As seen with naturally occurring IncA− mutants, light and immunofluorescence microscopy confirmed the presence of non-fusogenic inclusions in cells infected with the incA::GII(bla) mutants at a multiplicity of infection greater than one. Lack of IncA production by mutant clones was further confirmed by Western blotting. Ultimately, the ease of retargeting the intron, ability to select for mutants, and intron stability in the absence of selection makes this method a powerful addition to the growing chlamydial molecular toolbox.

Epigenetic regulation and cancer (Review)

'Epigenetics' is defined as the inheritable changes in gene expression with no alterations in DNA sequences. Epigenetics is a rapidly expanding field, and the study of epigenetic regulation in cancer is emerging. Disruption of the epigenome is a fundamental mechanism in cancer, and several epigenetic drugs have been proven to prolong survival and to be less toxic than conventional chemotherapy. Promising results from combination clinical trials with DNA methylation inhibitors and histone deacetylase inhibitors have recently been reported, and data are emerging that describe molecular determinants of clinical responses. Despite significant advances, challenges remain, including a lack of predictive markers, unclear mechanisms of response and resistance, and rare responses in solid tumors. Preclinical studies are ongoing with novel classes of agents that target various components of the epigenetic machinery. In the present review, examples of studies that demonstrate the role of epigenetic regulation in human cancers with the focus on histone modifications and DNA methylation, and the recent clinical and translational data in the epigenetics field that have potential in cancer therapy are discussed.

Reduced Cocaine Reinforcement in the Male Offspring of Cocaine-Experienced Sires

Mounting evidence suggests that parental ingestion of abused drugs influences the physiology and behavior of future generations in the absence of prenatal exposure (Vassoler et al, 2013a). However, few studies have examined potential mechanisms of transmission of addiction-related phenotypes. Therefore, we developed a rat model to delineate a heritable phenotype resulting from the self-administration of cocaine. Our research indicates that the sons of cocaine-experienced male rats find cocaine-less reinforcing, leading them to consume considerably less cocaine than controls (Vassoler et al, 2013b). Increased levels of cortical brain-derived neurotrophic factor (BDNF) may be the underlying cause of the cocaine resistance observed in the sons. These findings show that cocaine-induced changes in physiology can be inherited by sons from their fathers. The reason for the sex specificity is unclear, but may be due to intergenerational effects on gene transcription interacting with subsequent hormonal influences. We usually think about inherited changes in physiology occurring via natural selection on an evolutionary timescale. However, a growing body of evidence indicates that environmental information can be transmitted from one generation to the next. For example, epidemiological data show that a fetus exposed to famine early in pregnancy will tend to be born small but will be more prone to obesity, diabetes, and mental health issues as an adult (Lumey et al, 2011). Some of these health problems also plague the grandchildren of mothers malnourished in early pregnancy (Lumey et al, 2011). The latter is a potential example of epigenetic inheritance, defined as changes in phenotype caused by mechanisms other than alterations in DNA sequence. In our paradigm, male rats self-administered cocaine for 60 days (controls were administered saline) and were then paired with naive females. The offspring of these matings were tested for acquisition of cocaine self-administration. Our results indicated that the male, but not female, offspring of cocaine-experienced sires acquired cocaine self-administration more slowly and had decreased levels of cocaine intake relative to controls. Moreover, control animals were willing to work significantly harder for single cocaine infusions than the cocaine-sired rats, suggesting a decrease in the reinforcing effectiveness of cocaine. The cocaine-sired rats did not have generalized learning deficits, as there was no difference in acquisition of food self-administration. We next looked at BDNF expression in the prefrontal cortex of naive littermates. The cocaine-sired male offspring had increased histone acetylation association with a Bdnf promoter and augmented Bdnf mRNA, which enhanced BDNF protein levels in the prefrontal cortex. Importantly, blocking the action of BDNF reversed the cocaine-resistance phenotype. These findings raise the question of how paternal cocaine exposure influenced the behavior of the male offspring. Intriguingly, our results indicate that there were changes in histone acetylation of Bdnf promoters in the sperm of cocaine-experienced fathers, which might lead to increases in BDNF protein expression in the brains of the offspring. This finding indicates that cocaine causes epigenetic changes in sperm, which may alter the physiology and behavior of offspring in the absence of changes in DNA sequence. Taken together, these results indicate that paternal exposure to toxins such as cocaine can have profound effects on gene expression and behavior of the offspring.

Targeting Epigenetic Mechanisms for Clinical Translation: Enhancing the Efficacy of Tumor Immunotherapies

The ability to evade host immune surveillance is critical for the survival of tumor cells and is correlated with poor clinical outcomes. Many tumor types have been found to downregulate expression of genes involved in antigen production, processing and presentation to evade immune detection. Recent findings suggest that the mechanisms underlying these immune evasion phenomena extend beyond alterations in DNA sequence to include epigenetic modifications of DNA and associated proteins, including hypermethylation of DNA and altered histone acetylation patterns. This review will summarize alterations in antigen presentation machinery identified in malignant cells, epigenetic mechanisms that can be employed in the downregulation of genes relevant for antigen presentation and translational strategies to target these processes to enhance the efficacy of antitumor immunotherapies.

Decoding the Histone Code: Role of H3K36me3 in Mismatch Repair and Implications for Cancer Susceptibility and Therapy

DNA mismatch repair (MMR) maintains genome stability primarily by correcting replication-associated mismatches. Defects in MMR lead to several human cancers characterized by frequent alterations in simple repetitive DNA sequences, a phenomenon called microsatellite instability (MSI). In most MSI-positive cancers, genetic or epigenetic changes that alter the function or expression of an essential MMR protein have been identified. However, in a subset of MSI-positive cancers, epigenetic or genetic changes have not been found in known MMR genes, such that the molecular basis of the MMR defect in these cells remains unknown. A possible answer to this puzzle emerged recently when it was discovered that H3K36me3, a well-studied posttranslational histone modification or histone mark, plays a role in regulating human MMR in vivo. In this review, potential roles for this histone mark to modulate genome stability and cancer susceptibility in human cells are discussed.

Early environmental factors, alteration of epigenetic marks and metabolic disease susceptibility

The environmental conditions that are experienced in early life can profoundly influence human biology and long-term health. Early-life nutrition and stress are among the best documented examples of such conditions because they influence the adult risk of developing metabolic diseases, such as type 2 diabetes mellitus (T2D) and cardiovascular diseases. It is now becoming increasingly accepted that environmental compounds including nutrients can produce changes in the genome activity that in spite of not altering DNA sequence can produce important, stable and transgenerational alterations in the phenotype. Epigenetic changes, in particular DNA methylation and histone acetylation/methylation, provide a 'memory' of developmental plastic responses to early environment and are central to the generation of phenotypes and their stability throughout the life course. Their effects may only become manifest later in life, e.g. in terms of altered responses to environmental challenges.