scholarly journals RNA sequencing-based screen for reactivation of silenced alleles of autosomal genes

2021 ◽  
Author(s):  
Saumya Gupta ◽  
Denis L Lafontaine ◽  
Sebastien Vigneau ◽  
Asia Mendelevich ◽  
Svetlana Vinogradova ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Rna Sequencing ◽  
Mammalian Cells ◽  
Allelic Imbalance ◽  
Dna Demethylation ◽  
Monoallelic Expression ◽  
Specific Expression ◽  
Allele Specific ◽  
Mechanistic Basis

Abstract In mammalian cells, maternal and paternal alleles usually have similar transcriptional activity. Epigenetic mechanisms such as X-chromosome inactivation (XCI) and imprinting were historically viewed as rare exceptions to this rule. Discovery of autosomal monoallelic expression (MAE) a decade ago revealed an additional allele-specific mode regulating thousands of mammalian genes. Despite MAE prevalence, its mechanistic basis remains unknown. Using an RNA sequencing-based screen for reactivation of silenced alleles, we identified DNA methylation as key mechanism of MAE mitotic maintenance. In contrast with the all-or-nothing allelic choice in XCI, allele-specific expression in MAE loci is tunable, with exact allelic imbalance dependent on the extent of DNA methylation. In a subset of MAE genes, allelic imbalance was insensitive to DNA demethylation, implicating additional mechanisms in MAE maintenance in these loci. Our findings identify a key mechanism of MAE maintenance and provide basis for understanding the biological role of MAE.

scholarly journals DNA methylation is a key mechanism for maintaining monoallelic expression on autosomes

2020 ◽  
Author(s):  
Saumya Gupta ◽  
Denis L. Lafontaine ◽  
Sebastien Vigneau ◽  
Svetlana Vinogradova ◽  
Asia Mendelevich ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Monoallelic Expression ◽  
Specific Expression ◽  
Multiple Loci ◽  
Active Allele ◽  
Allele Specific ◽  
Small Molecule Screen ◽  
Mechanistic Basis ◽  
Diploid Cells

AbstractIn diploid cells, maternal and paternal copies of genes usually have similar transcriptional activity. Mammalian allele-specific epigenetic mechanisms such as X-chromosome inactivation (XCI) and imprinting were historically viewed as rare exceptions to this rule. The discovery of mitotically stable monoallelic autosomal expression (MAE) a decade ago revealed an additional allele-specific mode regulating thousands of mammalian genes. However, despite its prevalence, the mechanistic basis of MAE remains unknown. To uncover the mechanism of MAE maintenance, we devised a small-molecule screen for reactivation of silenced alleles across multiple loci using targeted RNA sequencing. Contrary to previous reports, we identified DNA methylation as a key mechanism of MAE mitotic maintenance. In contrast with the binary choice of the active allele in XCI, stringent transcriptome-wide analysis revealed MAE as a regulatory mode with tunable control of allele-specific expression, dependent on the extent of DNA methylation. In a subset of MAE genes, allelic imbalance was insensitive to changes in DNA methylation, implicating additional mechanisms in MAE maintenance in these loci. Our findings identify a key mechanism of MAE maintenance, reveal tunability of this mode of gene regulation, and provide the essential platform for probing the biological role of MAE in development and disease.

scholarly journals DNA Demethylation Pathways: Recent Insights

2013 ◽  
Vol 5 ◽  
pp. GEG.S12143 ◽  
Author(s):  
Cong-jun Li
Keyword(s):  
Dna Methylation ◽  
Mammalian Cells ◽  
De Novo ◽  
Dna Demethylation ◽  
Epigenetic Mark ◽  
Sequencing Technologies ◽  
Active Dna Demethylation ◽  
Mammalian Genomes ◽  
Genome Context

DNA methylation is a major epigenetic regulatory mechanism for gene expression and cell differentiation. Until recently, it was still unclear how unmethylated regions in mammalian genomes are protected from de novo methylation and whether or not active demethylating activity is involved. Even the role of molecules and the mechanisms underlying the processes of active demethylation itself is blurred. Emerging sequencing technologies have led to recent insights into the dynamic distribution of DNA methylation during development and the role of this epigenetic mark within a distinct genome context, such as the promoters, exons, or imprinted control regions. This review summarizes recent insights on the dynamic nature of DNA methylation and demethylation, as well as the mechanisms regulating active DNA demethylation in mammalian cells, which have been fundamental research interests in the field of epigenomics.

scholarly journals Unexpected variability of allelic imbalance estimates from RNA sequencing

2020 ◽  
Author(s):  
Asia Mendelevich ◽  
Svetlana Vinogradova ◽  
Saumya Gupta ◽  
Andrey A. Mironov ◽  
Shamil Sunyaev ◽  
...  
Keyword(s):  
Gene Expression ◽  
Rna Sequencing ◽  
Allelic Imbalance ◽  
Experimental Methods ◽  
Specific Gene ◽  
Differential Analysis ◽  
Specific Expression ◽  
Allele Specific Expression ◽  
Allele Specific ◽  
Noise Models

RNA sequencing and other experimental methods that produce large amounts of data are increasingly dominant in molecular biology. However, the noise properties of these techniques have not been fully understood. We assessed the reproducibility of allele-specific expression measurements by conducting replicate sequencing experiments from the same RNA sample. Surprisingly, variation in the estimates of allelic imbalance (AI) between technical replicates was up to 7-fold higher than expected from commonly applied noise models. We show that AI overdispersion varies substantially between replicates and between experimental series, appears to arise during the construction of sequencing libraries, and can be measured by comparing technical replicates. We demonstrate that compensation for AI overdispersion greatly reduces technical variation and enables reliable differential analysis of allele-specific expression across samples and across experiments. Conversely, not taking AI overdispersion into account can lead to a substantial number of false positives in analysis of allele-specific gene expression

scholarly journals Replicate sequencing libraries are important for quantification of allelic imbalance

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Asia Mendelevich ◽  
Svetlana Vinogradova ◽  
Saumya Gupta ◽  
Andrey A. Mironov ◽  
Shamil R. Sunyaev ◽  
...  
Keyword(s):  
Allelic Imbalance ◽  
False Positive Rate ◽  
Error Rates ◽  
Differential Analysis ◽  
Rna Seq ◽  
Specific Expression ◽  
Technical Noise ◽  
Specific Analysis ◽  
Positive Rate ◽  
Allele Specific

AbstractA sensitive approach to quantitative analysis of transcriptional regulation in diploid organisms is analysis of allelic imbalance (AI) in RNA sequencing (RNA-seq) data. A near-universal practice in such studies is to prepare and sequence only one library per RNA sample. We present theoretical and experimental evidence that data from a single RNA-seq library is insufficient for reliable quantification of the contribution of technical noise to the observed AI signal; consequently, reliance on one-replicate experimental design can lead to unaccounted-for variation in error rates in allele-specific analysis. We develop a computational approach, Qllelic, that accurately accounts for technical noise by making use of replicate RNA-seq libraries. Testing on new and existing datasets shows that application of Qllelic greatly decreases false positive rate in allele-specific analysis while conserving appropriate signal, and thus greatly improves reproducibility of AI estimates. We explore sources of technical overdispersion in observed AI signal and conclude by discussing design of RNA-seq studies addressing two biologically important questions: quantification of transcriptome-wide AI in one sample, and differential analysis of allele-specific expression between samples.

scholarly journals Unraveling the functional role of DNA methylation using targeted DNA demethylation by steric blockage of DNA methyltransferase with CRISPR/dCas9

2020 ◽  
Author(s):  
Daniel M. Sapozhnikov ◽  
Moshe Szyf
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Promoter Region ◽  
Dna Methyltransferase ◽  
Dna Demethylation ◽  
New Method ◽  
Inducible Promoters ◽  
Specific Targeting ◽  
Main Effect

AbstractAlthough associations between DNA methylation and gene expression were established four decades ago, the causal role of DNA methylation in gene expression remains unresolved. Different strategies to address this question were developed; however, all are confounded and fail to disentangle cause and effect. We developed here a highly effective new method using only deltaCas9(dCas9):gRNA site-specific targeting to physically block DNA methylation at specific targets in the absence of a confounding flexibly-tethered enzymatic activity, enabling examination of the role of DNA methylation per se in living cells. We show that the extensive induction of gene expression achieved by TET/dCas9-based targeting vectors is confounded by DNA methylation-independent activities, inflating the role of DNA methylation in the promoter region. Using our new method, we show that in several inducible promoters, the main effect of DNA methylation is silencing basal promoter activity. Thus, the effect of demethylation of the promoter region in these genes is small, while induction of gene expression by different inducers is large and DNA methylation independent. In contrast, targeting demethylation to the pathologically silenced FMR1 gene targets robust induction of gene expression. We also found that standard CRISPR/Cas9 knockout generates a broad unmethylated region around the deletion, which might confound interpretation of CRISPR/Cas9 gene depletion studies. In summary, this new method could be used to reveal the true extent, nature, and diverse contribution to gene regulation of DNA methylation at different regions.

scholarly journals Title Page Title: The role of DNA methylation in the accumulation of iridoid glycosides in Rehmannia glutinosa

2021 ◽  
Author(s):  
Tianyu Dong ◽  
Xiaoyan Wei ◽  
Qianting Qi ◽  
Peilei Chen ◽  
Yanqing Zhou ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Secondary Metabolites ◽  
Iridoid Glycosides ◽  
Methylation Status ◽  
Plant Secondary Metabolites ◽  
Dna Demethylation ◽  
Terpene Biosynthesis ◽  
The Relationship

Abstract Background: Epigenetic regulation plays a significant role in the accumulation of plant secondary metabolites. The terpenoids are the most abundant in the secondary metabolites of plants, iridoid glycosides belong to monoterpenoids which is one of the main medicinal components of R.glutinosa. At present, study on iridoid glycosides mainly focuses on its pharmacology, accumulation and distribution, while the mechanism of its biosynthesis and the relationship between DNA methylation and plant terpene biosynthesis are seldom reports. Results: The research showed that the expression of DXS, DXR, 10HGO, G10H, GPPS and accumulation of iridoid glycosides increased at first and then decreased with the maturity of R.glutinosa, and under different concentrations of 5-azaC, the expression of DXS, DXR, 10HGO, G10H, GPPS and the accumulation of total iridoid glycosides were promoted, the promotion effect of low concentration (15μM-50μM) was more significant, the content of genomic DNA 5mC decreased significantly, the DNA methylation status of R.glutinosa genomes was also changed. DNA demethylation promoted gene expression and increased the accumulation of iridoid glycosides, but excessive demethylation inhibited gene expression and decreased the accumulation of iridoid glycosides. Conclusion: The analysis of DNA methylation, gene expression, and accumulation of iridoid glycoside provides insights into accumulation of terpenoids in R.glutinosa and lays a foundation for future studies on the effects of epigenetics on the synthesis of secondary metabolites.

scholarly journals Genome-Wide Analysis of Allele-Specific Expression Patterns in Seventeen Tissues of Korean Cattle (Hanwoo)

Animals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 727
Author(s):  
Kyu-Sang Lim ◽  
Sun-Sik Chang ◽  
Bong-Hwan Choi ◽  
Seung-Hwan Lee ◽  
Kyung-Tai Lee ◽  
...  
Keyword(s):  
Phenotypic Variation ◽  
Expression Patterns ◽  
Monoallelic Expression ◽  
Specific Expression ◽  
Adult Cattle ◽  
Korean Cattle ◽  
Family Trio ◽  
Epigenetic Effects ◽  
Genome Wide ◽  
Allele Specific

The functional hemizygosity could be caused by the MAE of a given gene and it can be one of the sources to affect the phenotypic variation in cattle. We aimed to identify MAE genes across the transcriptome in Korean cattle (Hanwoo). For three Hanwoo family trios, the transcriptome data of 17 tissues were generated in three offspring. Sixty-two MAE genes had a monoallelic expression in at least one tissue. Comparing genotypes among each family trio, the preferred alleles of 18 genes were identified (maternal expression, n = 9; paternal expression, n = 9). The MAE genes are involved in gene regulation, metabolic processes, and immune responses, and in particular, six genes encode transcription factors (FOXD2, FOXM1, HTATSF1, SCRT1, NKX6-2, and UBN1) with tissue-specific expression. In this study, we report genome-wide MAE genes in seventeen tissues of adult cattle. These results could help to elucidate epigenetic effects on phenotypic variation in Hanwoo.

Effects of ten–eleven translocation 1 (Tet1) on DNA methylation and gene expression in chicken primordial germ cells

2019 ◽  
Vol 31 (3) ◽  
pp. 509 ◽  
Author(s):  
Minli Yu ◽  
Dongfeng Li ◽  
Wanyan Cao ◽  
Xiaolu Chen ◽  
Wenxing Du
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Germ Cells ◽  
Dna Methyltransferase ◽  
Primordial Germ Cells ◽  
Dna Demethylation ◽  
Caveolin 1 ◽  
Expression Of Genes ◽  
Deleted In Azoospermia

Ten–eleven translocation 1 (Tet1) is involved in DNA demethylation in primordial germ cells (PGCs); however, the precise regulatory mechanism remains unclear. In the present study the dynamics of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) in developing PGCs and the role of Tet1 in PGC demethylation were analysed. Results show that 5mC levels dropped significantly after embryonic Day 4 (E4) and 5hmC levels increased reaching a peak at E5–E5.5. Interestingly, TET1 protein was highly expressed during E5 to E5.5, which showed a consistent trend with 5hmC. The expression of pluripotency-associated genes (Nanog, PouV and SRY-box 2 (Sox2)) and germ cell-specific genes (caveolin 1 (Cav1), piwi-like RNA-mediated gene silencing 1 (Piwi1) and deleted in azoospermia-like (Dazl)) was upregulated after E5, whereas the expression of genes from the DNA methyltransferase family was decreased. Moreover, the Dazl gene was highly methylated in early PGCs and then gradually hypomethylated. Knockdown of Tet1 showed impaired survival and proliferation of PGCs, as well as increased 5mC levels and reduced 5hmC levels. Further analysis showed that knockdown of Tet1 led to elevated DNA methylation levels of Dazl and downregulated gene expression including Dazl. Thus, this study reveals the dynamic epigenetic reprogramming of chicken PGCs invivo and the molecular mechanism of Tet1 in regulating genomic DNA demethylation and hypomethylation of Dazl during PGC development.

scholarly journals Estimating the Allele-Specific Expression of SNVs From 10× Genomics Single-Cell RNA-Sequencing Data

Genes ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 240 ◽  
Author(s):  
Prashant N. M. ◽  
Hongyu Liu ◽  
Pavlos Bousounis ◽  
Liam Spurr ◽  
Nawaf Alomran ◽  
...  
Keyword(s):  
Single Cell ◽  
Rna Sequencing ◽  
Single Cells ◽  
Sequencing Data ◽  
Specific Expression ◽  
Single Nucleotide ◽  
Healthy Donors ◽  
Allele Expression ◽  
Single Cell Rna Sequencing ◽  
Allele Specific

With the recent advances in single-cell RNA-sequencing (scRNA-seq) technologies, the estimation of allele expression from single cells is becoming increasingly reliable. Allele expression is both quantitative and dynamic and is an essential component of the genomic interactome. Here, we systematically estimate the allele expression from heterozygous single nucleotide variant (SNV) loci using scRNA-seq data generated on the 10×Genomics Chromium platform. We analyzed 26,640 human adipose-derived mesenchymal stem cells (from three healthy donors), sequenced to an average of 150K sequencing reads per cell (more than 4 billion scRNA-seq reads in total). High-quality SNV calls assessed in our study contained approximately 15% exonic and >50% intronic loci. To analyze the allele expression, we estimated the expressed variant allele fraction (VAFRNA) from SNV-aware alignments and analyzed its variance and distribution (mono- and bi-allelic) at different minimum sequencing read thresholds. Our analysis shows that when assessing positions covered by a minimum of three unique sequencing reads, over 50% of the heterozygous SNVs show bi-allelic expression, while at a threshold of 10 reads, nearly 90% of the SNVs are bi-allelic. In addition, our analysis demonstrates the feasibility of scVAFRNA estimation from current scRNA-seq datasets and shows that the 3′-based library generation protocol of 10×Genomics scRNA-seq data can be informative in SNV-based studies, including analyses of transcriptional kinetics.

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