Littérature scientifique sur le sujet « Exonic DNA methylation »

DNA methylation is an epigenetic mechanism that regulates gene expression without altering gene sequences in health and disease. DNA methyltransferases (DNMTs) are enzymes responsible for DNA methylation, and their dysregulation is both a pathogenic mechanism of disease and a therapeutic target. DNMTs change gene expression by methylating CpG islands within exonic and intergenic DNA regions, which typically reduces gene transcription. Initially, mutations in the DNMT genes and pathologic DNMT protein expression were found to cause hematologic diseases, like myeloproliferative disease and acute myeloid leukemia, but recently they have been shown to promote cardiovascular diseases, including coronary artery disease and pulmonary hypertension. We reviewed the regulation and functions of DNMTs, with an emphasis on somatic mutations in DNMT3A, a common cause of clonal hematopoiesis of indeterminant potential (CHIP) that may also be involved in the development of pulmonary arterial hypertension (PAH). Accumulation of somatic mutations in DNMT3A and other CHIP genes in hematopoietic cells and cardiovascular tissues creates an inflammatory environment that promotes cardiopulmonary diseases, even in the absence of hematologic disease. This review summarized the current understanding of the roles of DNMTs in maintenance and de novo methylation that contribute to the pathogenesis of cardiovascular diseases, including PAH.

Disease risk is a persistent problem in domestic cattle farming, while economic traits are the main concern. This study aimed to reveal the epigenetic basis for differences between zebu (Bos indicus) and taurine cattle (Bos taurus) in disease, disease resistance, and economic traits, and provide a theoretical basis for the genetic improvement of domestic cattle. In this study, whole genome bisulfite sequencing (WGBS) was used to analyze the whole-genome methylation of spleen and liver samples from Yunnan zebu and Holstein cattle. In the genome-wide methylation pattern analysis, it was found that the methylation pattern of all samples was dominated by the CG type, which accounted for >94.9%. The DNA methylation levels of different functional regions and transcriptional elements in the CG background varied widely. However, the methylation levels of different samples in the same functional regions or transcriptional elements did not differ significantly. In addition, we identified a large number of differentially methylation region (DMR) in both the spleen and liver groups, of which 4713 and 4663 were annotated to functional elements, and most of them were annotated to the intronic and exonic regions of genes. GO and KEGG functional analysis of the same differentially methylation region (DMG) in the spleen and liver groups revealed that significantly enriched pathways were involved in neurological, disease, and growth functions. As a result of the results of DMR localization, we screened six genes (DNM3, INPP4B, PLD, PCYT1B, KCNN2, and SLIT3) that were tissue-specific candidates for economic traits, disease, and disease resistance in Yunnan zebu. In this study, DNA methylation was used to construct links between genotypes and phenotypes in domestic cattle, providing useful information for further screening of epigenetic molecular markers in zebu and taurine cattle.

Plant tissue culture is an in vitro technique used to manipulate cells, tissues, or organs, and plays an important role in genetic transformation. However, plants cultured in vitro often exhibit unintended genetic and epigenetic variations. Since it is important to secure the stability of endogenous and exogenous gene expressions in transgenic plants, it is preferable to avoid the occurrence of such variations. In this study, we focused on epigenetic variations, exclusively on methylation level changes of DNA, in transgenic Chinese cabbage (Brassica rapa ssp. pekinensis) plants. To detect these methylation level changes of DNA, bisulfite sequencing was performed and the obtained sequences were compared with the ‘CT001’ reference genome. Differentially methylated regions (DMRs) of DNA between the non-transgenic and transgenic lines were detected by bisulfite sequencing, and ten DMRs located in exonic regions were identified. The regions with methylation variations that were inherited and consistently maintained in the next generation lines were selected and validated. We also analyzed the relationship between methylation status and expression levels of transformant-conserved DMR (TCD) genes by quantitative reverse transcription-PCR. These results suggested that the changes in methylation levels of these DMRs might have been related to the plant transformation process, affecting subsequent gene expression. Our findings can be used in fundamental research on methylation variations in transgenic plants and suggest that these variations affect the expression of the associated genes.

Background: Cancer stem cells (CSCs) are considered the main cause of cancer recurrence and metastasis, and DNA methylation is involved in the maintenance of CSCs. However, the methylation profile of esophageal CSCs remains unknown. Methods: Side population (SP) cells were isolated from esophageal squamous cell carcinoma (ESCC) cell lines KYSE150 and EC109. Sphere-forming cells were collected from human primary esophageal cancer cells. SP cells and sphere-forming cells were used as substitutes for cancer stem-like cells. We investigated the genome-wide DNA methylation profile in esophageal cancer stem-like cells using reduced representation bisulfite sequencing (RRBS). Results: Methylated cytosine (mC) was found mostly in CpG dinucleotides, located mostly in the intronic, intergenic, and exonic regions. Forty intersected differentially methylated regions (DMRs) were identified in these 3 groups of samples. Thirteen differentially methylated genes with the same alteration trend were detected; these included OTX1, SPACA1, CD163L1, ST8SIA2, TECR, CADM3, GRM1, LRRK1, CHSY1, PROKR2, LINC00658, LOC100506688, and NKD2. DMRs covering ST8SIA2 and GRM1 were located in exons. These differentially methylated genes were involved in 10 categories of biological processes and 3 cell signaling pathways. Conclusions: When compared to non-CSCs, cancer stem-like cells have a differential methylation status, which provides an important biological base for understanding esophageal CSCs and developing therapeutic targets for esophageal cancer.

Abstract DNA N6-methyladenine (m6A) modification has been found widely presented in the human genome, and genome-wide DNA methylation profiling in cancer may reveal epigenetic signatures with significant clinical outcomes. Whole genome sequencing data from PacBio single-molecule real-time (SMRT) system provides signals for identifying the presence of m6A in human genomic DNA. We identified 343,199 m6A modification sites with an average density of 122 per Mb in the HCC1395 breast cancer cell line, whereas 722,303 m6A modification sites with average density of 257 per Mb were observed in a matched normal HCC1395BL cell line, meaning that the total number and the average density of m6A methylation sites in the cancer cell line were reduced more than 50% than that in normal cell line. Only small fraction of the methylation sites was found to be shared between the two cell lines, indicating that significant de-methylation (loss) and new methylation (gain) events occurred in HCC1395 cancer cells. A broad distribution of m6A methylation sites across autosomal chromosomes was observed, but the density of m6A methylation sites on chromosome X was extremely low for both HCC1395 and HCC1395BL cell lines. In contrast, the m6A densities on chromosome 7 and chromosome 22, particularly on their q-arms, from HCC1395 were substantially higher (hypermethylation) than other autosomal chromosomes, suggesting that copy number variations may be associated with these chromosomal regions. Most of the m6A methylation sites were located in intergenic and intronic regions, whereas only about 2~3% of the m6A methylation sites were situated in exonic regions, and 12% on ncRNAs. Understanding the genome-wide distinction of DNA methylation between cancer and matched normal cell lines makes it possible to ask more targeted questions and further investigate the role of methylation in cancer. Citation Format: Chunlin Xiao, Valerie Schneider. Genome-wide profiling of DNA N6-methylation from a breast cancer and a matched normal cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3743.

Phytoplasma-associated diseases such as phyllody and little leaf are critical threats to sesame cultivation worldwide. The mechanism of the dramatic conversion of flowers to leafy structures leading to yield losses and the drastic reduction in leaf size due to Phytoplasma infection remains yet to be identified. Cytosine methylation profiles of healthy and infected sesame plants studied using Whole Genome Bisulfite Sequencing (WGBS) and Quantitative analysis of DNA methylation with the real-time PCR (qAMP) technique revealed altered DNA methylation patterns upon infection. Phyllody was associated with global cytosine hypomethylation, though predominantly in the CHH (where H = A, T or C) context. Interestingly, comparable cytosine methylation levels were observed between healthy and little leaf-affected plant samples in CG, CHG and CHH contexts. Among the different genomic fractions, the highest number of differentially methylated Cytosines was found in the intergenic regions, followed by promoter, exonic and intronic regions in decreasing order. Further, most of the differentially methylated genes were hypomethylated and were mainly associated with development and defense-related processes. Loci for STOREKEEPER protein-like, a DNA-binding protein and PP2-B15, an F-Box protein, responsible for plugging sieve plates to maintain turgor pressure within the sieve tubes were found to be hypomethylated by WGBS, which was confirmed by methylation-dependent restriction digestion and qPCR. Likewise, serine/threonine-protein phosphatase-7 homolog, a positive regulator of cryptochrome signaling involved in hypocotyl and cotyledon growth and probable O-methyltransferase 3 locus were determined to be hypermethylated. Phytoplasma infection-associated global differential methylation as well as the defense and development-related loci reported here for the first time significantly elucidate the mechanism of phytoplasma-associated disease development.

Nucleosome positioning is not only related to genomic DNA compaction but also to other biological functions. After the chromatin is digested by micrococcal nuclease, nucleosomal (nucleosome-bound) DNA fragments can be sequenced and mapped on the genomic DNA sequence. Due to the development of modern DNA sequencing technology, genome-wide nucleosome mapping has been performed in a wide range of eukaryotic species. Comparative analyses of the nucleosome positions have revealed that the nucleosome is more frequently formed in exonic than intronic regions, and that most of transcription start and translation (or transcription) end sites are located in nucleosome linker DNA regions, indicating that nucleosome positioning influences transcription initiation, transcription termination, and gene splicing. In addition, nucleosomal DNA contains guanine and cytosine (G + C)-rich sequences and a high level of cytosine methylation. Thus, the nucleosome positioning system has been conserved during eukaryotic evolution.

Abstract The human lysozyme (LZM) gene, a marker gene for myeloid-specific development, is highly methylated in immature myeloid and in non-myeloid cells (all LZM-negative), and unmethylated in LZM-expressing mature phagocyte cells. Thus this gene provides an excellent model for investigating differentation-associated DNA methylation changes during myelopoiesis. There is now increasing evidence that LZM (containing five perfect consensus binding sites for AML1/RUNX1 in its 5′ region) is repressed by the AML1/ETO chimeric transcription factor (Fliegauf et al, Oncogene 23:9070–81, 2004), and this repression can be relieved by siRNA-mediated AML1/ETO depletion in AML1/ETO-positive Kasumi-1 cells (Dunne et al., Oncogene, 2006). Recently, AML1/ETO has also been implicated in gene-specific epigenetic repression of interleukin-3 (Liu et al, Cancer Res 65, 1277–84, 2005). By extensive methylation analyses of the LZM gene including bisulfite sequencing, we now demonstrate marked demethylation in both the CpG-poor 5′ region and the exonic CpG island after treatment of Kasumi-1 cells with non-cytotoxic concentrations of the DNA methyltransferase (DNMT) inhibitor 5-aza-2′-deoxycytidine (5-azaCdR), which was not associated with cellular differentiation. By Northern blot analysis, LZM mRNA levels in Kasumi-1 cells but not in AML1/ETO-negative HL-60 and U-937 cell lines were specifically and independently upregulated upon treatment with 5-azaCdR and, to a lesser extent, with the histone deacetylase (HDAC) inhibitor Trichostatin A (TSA). Combined treatment with subliminal concentrations of 5-azaCdR and TSA applied in different schedules did not reveal synergistic effects on LZM transcription. Relative chromatin accessibility of the LZM 5′ region, as detected by “MspI protection” assay, and associated with partial demethylation in several myeloid cell lines, was increased in Kasumi-1 with 5-azaCdR-induced further DNA demethylation, but not by TSA. As shown by chromatin immunoprecitation, TSA increased the acetylation of histones H3 and H4 both in the 5′ flanking region and exonic CpG island. In a U-937 inducible model, antagonization of AML1/ETO-mediated repression of LZM was achieved by TSA, implying that the histone deacetylation in this region of the human LZM gene is mediated by AML1/ETO protein. In conclusion, we demonstrate functional interactions between DNA methylation and histone modifications in mediating LZM gene repression which implicate AML1/ETO as one component involved in local chromatin remodelling. Interestingly, inhibitors of DNA methylation and histone deacetylation independently relieve repression of this CpG-poor gene in AML1/ETO-positive cells.

Drought stress remains one of the most detrimental environmental cues affecting plant growth and survival. In this work, the DNA methylome changes in mulberry leaves under drought stress (EG) and control (CK) and their impact on gene regulation were investigated by MethylRAD sequencing. The results show 138,464 (37.37%) and 56,241 (28.81%) methylation at the CG and CWG sites (W = A or T), respectively, in the mulberry genome between drought stress and control. The distribution of the methylome was prevalent in the intergenic, exonic, intronic and downstream regions of the mulberry plant genome. In addition, we discovered 170 DMGs (129 in CG sites and 41 in CWG sites) and 581 DMS (413 in CG sites and 168 in CWG sites). Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicates that phenylpropanoid biosynthesis, spliceosome, amino acid biosynthesis, carbon metabolism, RNA transport, plant hormone, signal transduction pathways, and quorum sensing play a crucial role in mulberry response to drought stress. Furthermore, the qRT-PCR analysis indicates that the selected 23 genes enriched in the KEGG pathways are differentially expressed, and 86.96% of the genes share downregulated methylation and 13.04% share upregulation methylation status, indicating the complex link between DNA methylation and gene regulation. This study serves as fundamentals in discovering the epigenomic status and the pathways that will significantly enhance mulberry breeding for adaptation to a wide range of environments.

Les rapides progrès technologiques en matière de techniques de biologie à grande échelle, comprenant notamment les microarrays, conduisent en 2006 au développement d’une nouvelle génération de puces à très haute résolution, capables de cibler à la fois tous les gènes du transcriptome humain, mais également tous les exons de ces gènes pris individuellement. L’avènement de cette puce, communément appelée puce exon, permit d’obtenir une mesure précise des changements transcriptomiques affectant les cellules cancéreuses, en offrant la possibilité de prendre en compte l’expression relative de différents exons d’un même gène.L’épissage alternatif et la transcription alternative sont les deux principaux mécanismes biologiques à l’origine de l’existence de plusieurs transcrits pour un même gène. Ces processus biologiques ont été mis en évidence depuis longtemps mais leur régulation dans les cellules normales ainsi que leurs dérégulations dans les cancers sont encore mal caractérisées de par la complexité des mécanismes impliqués. Par leur design, les puces exons permettent de mettre en évidence la présence de variations d’expression entre plusieurs transcrits potentiels d’un même gène, ouvrant ainsi la voie à une meilleure compréhension de ces processus biologiques.A partir d’un important jeu de données d’échantillons de cancers de la vessie dont le profil transcriptomique fut obtenu par puces exons, nous nous sommes intéressés à l’étude des changements d’épissage alternatif et à l’utilisation de promoteurs alternatifs dans les tumeurs de vessie. L’utilisation d’outils statistiques et mathématiques dédiés à l’analyse de ces puces nous a permis dans un premier temps d’identifier de nombreux gènes dont l’expression relative des différents transcrits est spécifiquement dérégulée dans les tumeurs de vessie. Ces transcrits constituent une nouvelle source pour l’identification de cibles thérapeutiques spécifiques des tumeurs. Nous avons pu montrer qu’avec une approche ciblée sur les changements d’expression relative de transcrits alternatifs d’un même gène, il était possible de constituer un panel de potentiels marqueurs tumoraux permettant le développement de nouveaux tests urinaires utiles à la détection des cancers de vessie et à la surveillance des patients.Par une analyse non supervisée des profils d’exons potentiellement dérégulés, nous avons pu observer une stratification des tumeurs similaire à celle observée par l’étude des profils géniques issus de puces classiques, confirmant alors l’existence d’un sous groupe de tumeurs de vessie présentant des caractéristiques transcriptomiques propres. Nous avons pu associer à ce sous-groupe de mauvais pronostic, une signature d’inclusion différentielle de certains exons. Cette signature impliquant 19 gènes permet d’identifier précisément ces tumeurs de manière très spécifique et constitue par conséquent un outil puissant utilisable en clinique.L’étude ciblée d’une voie de signalisation fréquemment dérégulée dans les cancers nous a permis de mettre en évidence une dérégulation globale de l’expression relative des transcrits alternatifs de gènes impliqués dans la prolifération cellulaire, et d’en identifier de probables régulateurs. Enfin, L’analyse des données de puces exons à la lumière des données de méthylation de l’ADN nous a permis d’identifier un mécanisme épigénétique régulant l’utilisation de promoteurs alternatifs dans un sous-groupe de tumeurs de vessie.L’ensemble des résultats obtenus par l’analyse de ces puces exons a par conséquent permis de caractériser à l’échelle du transcrit les dérégulations spécifiques des tumeurs de vessie, et d’en identifier certains mécanismes. Ces dérégulations permettent non seulement d’identifier spécifiquement plusieurs sous-groupe de tumeurs dont un de mauvais pronostic, mais offrent également de nouvelles possibilités quant-à la recherche de marqueurs urinaires pour la surveillance des patients
The development of microarray technology in the late 1990’s served as an essential tool to comprehend the scope of transcriptomic deregulations occurring in cancer cells. Signals generated from the first generation of transcriptomic microarrays gave simultaneous measures of expression from a large number of genes, therefore enabling to identify candidate genes involved in cancer progression and putative therapeutic targets. In 2006, through a fast de- velopment of high-throughput technologies, the available large scale analysis tools became enriched with a new generation of high resolution microarrays measuring expression signals both at the gene-level and at the exon-level of each gene. The advent of this high-resolution microarray, commonly called exon array, provided the opportunity to get a more accurate meas- ure of transcriptomic changes affecting cancer cells by enabling to consider relative expression changes of the exons from a same gene.Alternative splicing and alternative transcription are the two main biological mechanisms accounting for the production of several transcripts from a same gene. Although these bio- logical processes have been known for a long time, their regulation in normal cells and their deregulation in cancer still remain challenging to well-characterize, mainly due to the complex- ity of the involved mechanisms. Through their design, exon arrays enable to identify variable expression patterns within several potential transcripts of a same gene, therefore bringing new insight into these biological processes.Based on a large dataset of bladder cancer samples that were profiled on exon arrays, we focused on the study of alternative splicing changes and alternative promoter usage in bladder tumours. Analysis of these exon arrays through the use of adapted statistical and mathemat- ical tools initially resulted in the identification of numerous genes showing differential relative expression patterns of their transcripts between cancer and normal samples. These transcripts represent a new opportunity to define tumour-specific therapeutic targets. We demonstrated that using an approach targeted on relative expression changes of transcripts from a same gene, it was possible to build up a panel of potential tumour-specific markers enabling the development of new urinary test to detect bladder cancer and monitor its evolution.Through an unsupervised analysis of putatively deregulated exon profiles, we observed that the partitioning of bladder tumours was similar to the classification resulting from the study of classical gene microarray expression profiles, consequently confirming the existence of a bladder subgroup with peculiar transcriptomic properties. For this subgroup of bad prognosis, we established a signature based on the differential alternative inclusion of several exons. This signature relates to 19 genes and enables to accurately identify tumours from this subgroup, therefore providing a powerful tool to be used in clinical practice.By studying a specific pathway often deregulated in cancer, we highlighted an overall dereg- ulation of the relative expression of alternative transcripts from genes involved in cell prolifer- ation, and identified potential actors involved in the underlying regulatory process. Eventually, the analysis of exon arrays in the light of DNA methylation array data enabled us to identify an epigenetic mechanism regulating the use of alternative promoters in a subgroup of bladder tumours.Together, the results obtained from exon array analysis consequently provided a character- ization at the transcript level of bladder tumour specific deregulations and brought insight into the underlying mechanisms. The highlighted deregulations not only allow to accurately identify two subgroups of tumours, of which one has a bad prognosis, but also offer new possibilities regarding the definition of urinary markers for patient monitoring

DNA methylation is an epigenetic modification that consists of the addition of a methyl, or of a hydroxyl and a methyl group, to the cytosine of CpG dinucleotides. Some gene promoters are rich in CpGs that are predominantly not modified; other promoters and most enhancers are poor in CpGs. These elements, as well as most exons, introns and intergenic regions, tend to be methylated. CpG methylation plays an important role in maintaining transposable elements and tandem arrays of repetitive sequences in a repressed state. CpG methylation is also responsible for the uniparental silencing of imprinted alleles, allowing the monoallelic expression of some genes, and for the silencing and clonal transmission of the inactive X chromosome in mammals. The use of this modification as a means of dynamically turning individual genes on or off, illustrated by the activation of individual odorant receptor genes, is less common.