scholarly journals Stochastic epigenetic mutations (DNA methylation) increase exponentially in human aging and correlate with X chromosome inactivation skewing in females

Aging ◽  
2015 ◽  
Vol 7 (8) ◽  
pp. 568-578 ◽  
Author(s):  
Davide Gentilini ◽  
Paolo Garagnani ◽  
Serena Pisoni ◽  
Maria Giulia Bacalini ◽  
Luciano Calzari ◽  
...  
Keyword(s):  
Dna Methylation ◽  
X Chromosome ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Human Aging

Changes in DNA methylation during mouse embryonic development in relation to X-chromosome activity and imprinting

1990 ◽  
Vol 326 (1235) ◽  
pp. 299-312 ◽  
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Embryonic Development ◽  
X Chromosome ◽  
De Novo ◽  
Germ Line ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Chromatin Configuration ◽  
Methylation Patterns

Changing DNA methylation patterns during embryonic development are discussed in relation to differential gene expression, changes in X-chromosome activity and genomic imprinting. Sperm DNA is more methylated than oocyte DNA, both overall and for specific sequences. The methylation difference between the gametes could be one of the mechanisms (along with chromatin structure) regulating initial differences in expression of parental alleles in early development. There is a loss of methylation during development from the morula to the blastocyst and a marked decrease in methylase activity. De novo methylation becomes apparent around the time of implantation and occurs to a lesser extent in extra-embryonic tissue DNA. In embryonic DNA, de novo methylation begins at the time of random X-chromosome inactivation but it continues to occur after X-chromosome inactivation and may be a mechanism that irreversibly fixes specific patterns of gene expression and X-chromosome inactivity in the female. The germ line is probably delineated before extensive de novo methylation and hence escapes this process. The marked undermethylation of the germ line DNA may be a prerequisite for X-chromosome reactivation. The process underlying reactivation and removal of parent-specific patterns of gene expression may be changes in chromatin configuration associated with meiosis and a general reprogramming of the germ line to developmental totipotency.

scholarly journals DNA metylation as one of the main mechanisms of gene activity regulation

2004 ◽  
Vol 2 (1) ◽  
pp. 27-37
Author(s):  
Anna A Pendina ◽  
Vera V Grinkevich ◽  
Tatyana V Kuznetsova ◽  
Vladislav S Baranov
Keyword(s):  
Dna Methylation ◽  
Genomic Imprinting ◽  
X Chromosome ◽  
Epigenetic Inheritance ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Gene Repression ◽  
Activity Regulation ◽  
Inherited Diseases

 DNA methylation is one of the main mechanisms of epigenetic inheritance in eukaryotes. In this review we looked through the ways of 5-methylcytosin origin, it's distribution in genome, the mechanism of gene repression via hypermetilation, the role of metylation in genomic imprinting and in X-chromosome inactivation, in embryogenesis of mammals, in the processes of oncogenesis and in etiology of some common human inherited diseases

scholarly journals Contribution of genetic and epigenetic changes to escape from X-chromosome inactivation

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Bradley P. Balaton ◽  
Carolyn J. Brown
Keyword(s):  
Dna Methylation ◽  
X Chromosome ◽  
Cpg Islands ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Status Change ◽  
Epigenetic Marks ◽  
Individual Gene ◽  
Inactive X Chromosome ◽  
The Individual

Abstract Background X-chromosome inactivation (XCI) is the epigenetic inactivation of one of two X chromosomes in XX eutherian mammals. The inactive X chromosome is the result of multiple silencing pathways that act in concert to deposit chromatin changes, including DNA methylation and histone modifications. Yet over 15% of genes escape or variably escape from inactivation and continue to be expressed from the otherwise inactive X chromosome. To the extent that they have been studied, epigenetic marks correlate with this expression. Results Using publicly available data, we compared XCI status calls with DNA methylation, H3K4me1, H3K4me3, H3K9me3, H3K27ac, H3K27me3 and H3K36me3. At genes subject to XCI we found heterochromatic marks enriched, and euchromatic marks depleted on the inactive X when compared to the active X. Genes escaping XCI were more similar between the active and inactive X. Using sample-specific XCI status calls, we found some marks differed significantly with variable XCI status, but which marks were significant was not consistent between genes. A model trained to predict XCI status from these epigenetic marks obtained over 75% accuracy for genes escaping and over 90% for genes subject to XCI. This model made novel XCI status calls for genes without allelic differences or CpG islands required for other methods. Examining these calls across a domain of variably escaping genes, we saw XCI status vary across individual genes rather than at the domain level. Lastly, we compared XCI status calls to genetic polymorphisms, finding multiple loci associated with XCI status changes at variably escaping genes, but none individually sufficient to induce an XCI status change. Conclusion The control of expression from the inactive X chromosome is multifaceted, but ultimately regulated at the individual gene level with detectable but limited impact of distant polymorphisms. On the inactive X, at silenced genes euchromatic marks are depleted while heterochromatic marks are enriched. Genes escaping inactivation show a less significant enrichment of heterochromatic marks and depletion of H3K27ac. Combining all examined marks improved XCI status prediction, particularly for genes without CpG islands or polymorphisms, as no single feature is a consistent feature of silenced or expressed genes.

scholarly journals Artificial escape from XCI by DNA methylation editing of the CDKL5 gene

2020 ◽  
Vol 48 (5) ◽  
pp. 2372-2387 ◽  
Author(s):  
Julian A N M Halmai ◽  
Peter Deng ◽  
Casiana E Gonzalez ◽  
Nicole B Coggins ◽  
David Cameron ◽  
...  
Keyword(s):  
Dna Methylation ◽  
X Chromosome ◽  
Catalytic Domain ◽  
Epigenetic Modification ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Promoter Regions ◽  
Cpg Dinucleotides ◽  
Active Allele ◽  
Infantile Epilepsy

Abstract A significant number of X-linked genes escape from X chromosome inactivation and are associated with a distinct epigenetic signature. One epigenetic modification that strongly correlates with X-escape is reduced DNA methylation in promoter regions. Here, we created an artificial escape by editing DNA methylation on the promoter of CDKL5, a gene causative for an infantile epilepsy, from the silenced X-chromosomal allele in human neuronal-like cells. We identify that a fusion of the catalytic domain of TET1 to dCas9 targeted to the CDKL5 promoter using three guide RNAs causes significant reactivation of the inactive allele in combination with removal of methyl groups from CpG dinucleotides. Strikingly, we demonstrate that co-expression of TET1 and a VP64 transactivator have a synergistic effect on the reactivation of the inactive allele to levels >60% of the active allele. We further used a multi-omics assessment to determine potential off-targets on the transcriptome and methylome. We find that synergistic delivery of dCas9 effectors is highly selective for the target site. Our findings further elucidate a causal role for reduced DNA methylation associated with escape from X chromosome inactivation. Understanding the epigenetics associated with escape from X chromosome inactivation has potential for those suffering from X-linked disorders.

scholarly journals Use of a HpaII-polymerase chain reaction assay to study DNA methylation in the Pgk-1 CpG island of mouse embryos at the time of X-chromosome inactivation.

1990 ◽  
Vol 10 (9) ◽  
pp. 4987-4989 ◽  
Author(s):  
J Singer-Sam ◽  
M Grant ◽  
J M LeBon ◽  
K Okuyama ◽  
V Chapman ◽  
...  
Keyword(s):  
Dna Methylation ◽  
X Chromosome ◽  
Inner Cell Mass ◽  
Cpg Island ◽  
Cell Mass ◽  
X Chromosome Inactivation ◽  
Mouse Embryos ◽  
Chromosome Inactivation ◽  
Individual Mouse ◽  
Polymerase Chain

A HpaII-PCR assay was used to study DNA methylation in individual mouse embryos. It was found that HpaII site H-7 in the CpG island of the X-chromosome-linked Pgk-1 gene is less than or equal to 10% methylated in oocytes and male embryos but becomes 40% methylated in female embryos at 6.5 days; about the time of X-chromosome inactivation of the inner cell mass.

scholarly journals Regulation of X-Chromosome Inactivation in Development in Mice and Humans

1998 ◽  
Vol 62 (2) ◽  
pp. 362-378 ◽  
Author(s):  
Tetsuya Goto ◽  
Marilyn Monk
Keyword(s):  
Dna Methylation ◽  
X Chromosome ◽  
Regulatory Gene ◽  
X Chromosome Inactivation ◽  
Xist Gene ◽  
Chromosome Inactivation ◽  
Preimplantation Embryos ◽  
Paternal Allele ◽  
Inactive X Chromosome ◽  
Extraembryonic Tissues

SUMMARY Dosage compensation for X-linked genes in mammals is accomplished by inactivating one of the two X chromosomes in females. X-chromosome inactivation (XCI) occurs during development, coupled with cell differentiation. In somatic cells, XCI is random, whereas in extraembryonic tissues, XCI is imprinted in that the paternally inherited X chromosome is preferentially inactivated. Inactivation is initiated from an X-linked locus, the X-inactivation center (Xic), and inactivity spreads along the chromosome toward both ends. XCI is established by complex mechanisms, including DNA methylation, heterochromatinization, and late replication. Once established, inactivity is stably maintained in subsequent cell generations. The function of an X-linked regulatory gene, Xist, is critically involved in XCI. The Xist gene maps to the Xic, it is transcribed only from the inactive X chromosome, and the Xist RNA associates with the inactive X chromosome in the nucleus. Investigations with Xist-containing transgenes and with deletions of the Xist gene have shown that the Xist gene is required in cis for XCI. Regulation of XCI is therefore accomplished through regulation of Xist. Transcription of the Xist gene is itself regulated by DNA methylation. Hence, the differential methylation of the Xist gene observed in sperm and eggs and its recognition by protein binding constitute the most likely mechanism regulating imprinted preferential expression of the paternal allele in preimplantation embryos and imprinted paternal XCI in extraembryonic tissues. This article reviews the mechanisms underlying XCI and recent advances elucidating the functions of the Xist gene in mice and humans.

scholarly journals DAMEfinder: A method to detect differential allele-specific methylation

2019 ◽  
Author(s):  
Stephany Orjuela ◽  
Dania Machlab ◽  
Mirco Menigatti ◽  
Giancarlo Marra ◽  
Mark D. Robinson
Keyword(s):  
Colorectal Cancer ◽  
Dna Methylation ◽  
X Chromosome ◽  
Regulation Of Gene Expression ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Cancer Dataset ◽  
Cpg Sites ◽  
Allele Specific ◽  
Allele Specific Methylation

AbstractDNA methylation is a highly studied epigenetic signature that is associated with regulation of gene expression, whereby genes with high levels of promoter methylation are generally repressed. Genomic imprinting occurs when one of the parental alleles is methylated, i.e, when there is inherited allele-specific methylation (ASM). A special case of imprinting occurs during X chromosome inactivation in females, where one of the two X chromosomes is silenced, in order to achieve dosage compensation between the sexes. Another more widespread form of ASM is sequence dependent (SD-ASM), where ASM is linked to a nearby heterozygous single nucleotide polymorphism (SNP).We developed a method to screen for genomic regions that exhibit loss or gain of ASM in samples from two conditions (treatments, diseases, etc.). The method relies on the availability of bisulfite sequencing data from multiple samples of the two conditions. We leverage other established computational methods to screen for these regions within a new R package called DAMEfinder. It calculates an ASM score for all CpG sites or pairs in the genome of each sample, and then quantifies the change in ASM between conditions. It then clusters nearby CpG sites with consistent change into regions.In the absence of SNP information, our method relies only on reads to quantify ASM. This novel ASM score compares favourably to current methods that also screen for ASM. Not only does it easily discern between imprinted and non-imprinted regions, but also females from males based on X chromosome inactivation. We also applied DAMEfinder to a colorectal cancer dataset and observed that colorectal cancer subtypes are distinguishable according to their ASM signature. We also re-discover known cases of loss of imprinting.We have designed DAMEfinder to detect regions of differential ASM (DAMEs), which is a more refined definition of differential methylation, and can therefore help in breaking down the complexity of DNA methylation and its influence in development and disease.

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