Epigenetic Control Systems Research Articles

Molecular biology of the cell

Molecular biology of the cell

Epigenetic control of abiotic stress signaling in plants.

Although plants may be regularly exposed to various abiotic stresses, including drought, salt, cold, heat, heavy metals, and UV-B throughout their lives, it is not possible to actively escape from such stresses due to the immobile nature of plants. To overcome adverse environmental stresses, plants have developed adaptive systems that allow appropriate responses to diverse environmental cues; such responses can be achieved by fine-tuning or controlling genetic and epigenetic regulatory systems. Epigenetic mechanisms such as DNA or histone modifications and modulation of chromatin accessibility have been shown to regulate the expression of stress-responsive genes in struggles against abiotic stresses. Herein, the current progress in elucidating the epigenetic regulation of abiotic stress signaling in plants has been summarized in order to further understand the systems plants utilize to effectively respond to abiotic stresses. This review focuses on the action mechanisms of various components that epigenetically regulate plant abiotic stress responses, mainly in terms of DNA methylation, histone methylation/acetylation, and chromatin remodeling. This review can be considered a basis for further research into understanding the epigenetic control system for abiotic stress responses in plants. Moreover, the knowledge of such systems can be effectively applied in developing novel methods to generate abiotic stress resistant crops.

Dynamic methylation of histone H3K18 in differentiating Theileria parasites

Lysine methylation on histone tails impacts genome regulation and cell fate determination in many developmental processes. Apicomplexa intracellular parasites cause major diseases and they have developed complex life cycles with fine-tuned differentiation events. Yet, apicomplexa genomes have few transcription factors and little is known about their epigenetic control systems. Tick-borne Theileria apicomplexa species have relatively small, compact genomes and a remarkable ability to transform leucocytes in their bovine hosts. Here we report enriched H3 lysine 18 monomethylation (H3K18me1) on the gene bodies of repressed genes in Theileria macroschizonts. Differentiation to merozoites (merogony) leads to decreased H3K18me1 in parasite nuclei. Pharmacological manipulation of H3K18 acetylation or methylation impacted parasite differentiation and expression of stage-specific genes. Finally, we identify a parasite SET-domain methyltransferase (TaSETup1) that can methylate H3K18 and represses gene expression. Thus, H3K18me1 emerges as an important epigenetic mark which controls gene expression and stage differentiation in Theileria parasites.

PH-controlled histone acetylation amplifies melanocyte differentiation downstream of MITF.

Tanning response and melanocyte differentiation are mediated by the central transcription factor MITF. This involves the rapid and selective induction of melanocyte maturation genes, while concomitantly the expression of other effector genes is maintained. In this study, using cell-based and zebrafish model systems, we report on a pH-mediated feed-forward mechanism of epigenetic regulation that enables selective amplification of the melanocyte maturation program. We demonstrate that MITF activation directly elevates the expression of the enzyme carbonic anhydrase 14 (CA14). Nuclear localization of CA14 leads to an increase of the intracellular pH, resulting in the activation of the histone acetyl transferase p300/CBP. In turn, enhanced H3K27 histone acetylation at selected differentiation genes facilitates their amplified expression via MITF. CRISPR-mediated targeted missense mutation of CA14 in zebrafish results in the formation of immature acidic melanocytes with decreased pigmentation, establishing a central role for this mechanism during melanocyte differentiation invivo. Thus, we describe an epigenetic control system via pH modulation that reinforces cell fate determination by altering chromatin dynamics.

Chemical Control System of Epigenetics.

Epigenetics represents the inheritable changes to the chemical control system governing the gene expression with no ensuing changes to the underlying DNA sequence. Environment-mediated modification of the natural epigenetic interactions can perturb the cellular homeostasis and drive cells to a diseased state by switching therapeutically essential genes ON and OFF. Contemporary bioinformatics tools have revealed the structural chemical modifications of the epigenetic enzymes associated with several complex diseases, including cancers, immune disorders, and neurodegenerative disorders at the fundamental level. The amenable nature of the epigenetic enzymes to chemical modifications aided the screening and identification of synthetic small-molecule inhibitors. Continuing the current steady progress in the development of these small-molecule inhibitors as 'epi-drugs' in preclinical studies requires further advances to enable existing clinical barriers to be overcome. Recently, an epigenetic modifier complemented with selective DNA-binding small molecules was shown to function as an artificial biomimetic epigenetic code. Herein, we summarize the chemical aspects of the natural epigenetic control system and detail the recent advances in the synthetic strategies to mimic the genetic and epigenetic control system.

Epi-fingerprinting and epi-interventions for improved crop production and food quality.

Increasing crop production at a time of rapid climate change represents the greatest challenge facing contemporary agricultural research. Our understanding of the genetic control of yield derives from controlled field experiments designed to minimize environmental variance. In spite of these efforts there is substantial residual variability among plants attributable to Genotype × Environment interactions. Recent advances in the field of epigenetics have revealed a plethora of gene control mechanisms that could account for much of this unassigned variation. These systems act as a regulatory interface between the perception of the environment and associated alterations in gene expression. Direct intervention of epigenetic control systems hold the enticing promise of creating new sources of variability that could enhance crop performance. Equally, understanding the relationship between various epigenetic states and responses of the crop to specific aspects of the growing environment (epigenetic fingerprinting) could allow for a more tailored approach to plant agronomy. In this review, we explore the many ways in which epigenetic interventions and epigenetic fingerprinting can be deployed for the improvement of crop production and quality.

Epigenetic Analysis and Suitability of Amniotic Fluid Stem Cells for Research and Therapeutic Purposes

Amniotic fluid stem cells (AFSs) are interesting mesenchymal stem cells (MSCs) that are characterized by their great potential for cell proliferation and differentiation compared with other types of MSCs identified to date. However, MSCs in prolonged culture have been found to exhibit defects in genetic stability and differentiation capacity. Epigenetic anomalies have been hypothesized to be a cause of these defects. Here, we investigated the genomic methylation and genetic imprinting in AFSs during prolonged in vitro culture. Four human imprinted genes, insulin-like growth factor 2 (IGF2), H19, small nuclear ribonucleoprotein polypeptide N gene (SNRPN), and mesoderm-specific transcript (MEST), were evaluated for their expression levels and methylation statuses in AFS lines. The data revealed epigenetic instability in high passage number AFS cultures. The real-time polymerase chain reaction analysis showed that the expression levels of the imprinted genes gradually increased with increased time in culture. The loss of parental allele-specific imprinting for at least 1 gene among IGF2, H19, and SNRPN was observed in every AFS line after passage 8 using allelic expression analysis. The imprinting control regions (ICRs) of the IGF2 and H19 genes were assayed for site-specific methylation using bisulfite sequencing. This assay revealed a variable level of methylated CpG sites in the ICRs of IGF2 and H19. This variable level of CpG methylation is related to the aberrant expression of the IGF2 and H19 genes in late-passage AFSs. Our results did not reveal any irregularity in the epigenetic control system in the early-passage AFSs, indicating that the standard in vitro culturing of AFSs used in medical treatments should be limited to 8 passages.

Class I and III HDACs and loss of active chromatin features contribute to epigenetic silencing of CDX1 and EPHB tumor suppressor genes in colorectal cancer

Aberrant Wnt/β-catenin signaling is a driving force during initiation and progression of colorectal cancer. Yet, the Wnt/β-catenin targets CDX1, EPHB2, EPHB3 and EPHB4 (EPHB2-4) act as tumor suppressors in intestinal epithelial cells and frequently appear to be transcriptionally silenced in carcinomas. The molecular mechanisms which underlie the apparent loss of expression of a subset of Wnt/β-catenin targets in a background of persistent pathway activity are largely unknown. To gain insight into this, we quantified expression of CDX1 and EPHB2-4 in human tissue specimens of case-matched colorectal normal mucosa, adenoma and invasive carcinoma. In particular EPHB2-4 display biphasic, albeit not strictly coincident, expression profiles with elevated levels in adenomas and decreased transcription in approximately 30% of the corresponding carcinomas. Consistent with their divergent and variable expression we observed considerable heterogeneity among the epigenetic landscapes at CDX1 and EPHB2-4 in a model of colorectal carcinoma cell lines. Unlike the inactive CDX1 locus, EPHB2-4 maintain DNA hypomethylation of their promoter regions in the silent state. A strong reduction of active histone modifications consistently parallels reduced expression of CDX1 and EPHB3 and to some extent of EPHB2. Accordingly, treatment with inhibitors for DNA methyltransferases (DNMTs) and histone deacetylases(HDACs) restored CDX1 and EPHB2-4 expression depending upon epigenetic features at their promoters but also upon cellular background. Overall our findings show that downregulation of CDX1 and EphB receptor genes occurs independently and that different branches of epigenetic control systems including class I and III HDACs contribute to epigenetic silencing of Wnt/β-catenin targets during colorectal tumorigenesis.

Soft inheritance: challenging the modern synthesis

This paper presents some of the recent challenges to the Modern Synthesis of evolutionary theory, which has dominated evolutionary thinking for the last sixty years. The focus of the paper is the challenge of soft inheritance - the idea that variations that arise during development can be inherited. There is ample evidence showing that phenotypic variations that are independent of variations in DNA sequence, and targeted DNA changes that are guided by epigenetic control systems, are important sources of hereditary variation, and hence can contribute to evolutionary changes. Furthermore, under certain conditions, the mechanisms underlying epigenetic inheritance can also lead to saltational changes that reorganize the epigenome. These discoveries are clearly incompatible with the tenets of the Modern Synthesis, which denied any significant role for Lamarckian and saltational processes. In view of the data that support soft inheritance, as well as other challenges to the Modern Synthesis, it is concluded that that synthesis no longer offers a satisfactory theoretical framework for evolutionary biology.

Evolution of mammal epigenetic control systems

Evolution of mammal epigenetic control systems

Order and disorder in biological systems through negative cross-diffusion of mitotic inhibitor—a mathematical model

A negative feedback epigenetic control system involving synthesis of the mitotic inducing and inhibiting proteins, simultaneously with the intercellular self-diffusion and cross-diffusion of the latter only have been proposed in this paper. By this model we can explain clearly the mechanisms of three types of cellular development, namely, ordered structure during embryonic development, normal tissue growth and tumor growth, respectively, for different ranges of values of the ratio of self-diffusion and cross-diffusion.

Morphogenetic prepattern during embryonic development—a nonlinear analysis

By considering a nonlinear reaction-diffusion negative feedback epigenetic control system, involving synthesis of the mitotic-inducing and inhibiting proteins simultaneously with intercellular self-diffusion and negative cross-diffusion of the latter only, Tapaswi and Saha [1] have showed the system generates a Turing structure during embryonic development. In this paper, we have observed, by using Lyapunov's direct method, that the pattern, thus generated, is globally asymptotically stable.

Formation of a regular dissipative structure: a bifurcation and non-linear analysis

A non-linear reaction diffusion model of a negative feedback epigenetic control system is presented. The model involves synthesis of the mitotic inducing and inhibiting proteins, simultaneously with intercellular self-diffusion and cross-diffusion of the latter only. The importance of negative cross-diffusion for creating a regular dissipative structure is shown. A bifurcation analysis of the non-linear diffusive system has been performed and it is concluded that bifurcation is supercritical. Lastly, using Liapunov's direct method, it is shown that the pattern evolved by the system is globally asymptotically stable.

Simulation Models for the Dynamic Analysis of Molecular‐Genetic Control Systems. Part 2: Application of the discrete stochastic model to the system analysis of some elementary epigenetic control systems

AbstractThe discrete stochastic model of the gene‐expression regulation — elaborated in the first part of this work — is used for the dynamic analysis of some simple molecular‐genetic control systems. The aim is the determination of stationary states and of their stability behaviour, the finding and understanding of the functional properties of the dynamics of epigenetic systems and the study of the integral behaviour (reliability) in case of stochastically disturbed single processes.Connections between simple processes of the gene‐expression and partial sections of the secondary differentiation are investigated and an approach for the formal description of the overlapping and time coordination of simple differentiation programs are described.For the mutant Lambda sus O29, which is unable to replicate, the regulation of the early development is investigated and a good congruence between experimental and theoretical results is obtained. Predictions on a hypothetic mutant and suggestions for experiments are made.