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Background: The human placenta is distinct from most organs due to its uniquely low-methylated genome. DNA methylation (DNAme) is particularly depleted in the placenta at partially methylated domains and on the inactive X chromosome (Xi) in XX samples. While Xi DNAme is known to be critical for X-chromosome inactivation (XCI) in other tissues, its role in the placenta remains unclear. Understanding X-linked DNAme variation in the placenta may provide insights into XCI and have implications for prenatal development and phenotypic sex differences.
Methods: DNAme data were analyzed from over 350 human placental (chorionic villus) samples, along with samples from cord blood, amnion and chorion placental membranes, and fetal somatic tissues. We characterized X chromosome DNAme variation in the placenta relative to sample variables including cell composition, ancestry, maternal age, placental weight, and fetal birth weight, and compared these patterns to other tissues. We also evaluated the relationship between X-linked DNAme and previously reported XCI gene expression status in placenta.
Results: Our findings confirm that the placenta exhibits significant depletion of DNAme on the Xi compared to other tissues. Additionally, we observe that X chromosome DNAme profiles in the placenta are influenced by cell composition, particularly trophoblast proportion, with minimal DNAme variation across gestation. Notably, low promoter DNAme is observed at most genes on the Xi regardless of XCI status, challenging known associations in somatic tissues between low promoter DNAme and escape from XCI.
Conclusions: This study provides evidence that the human placenta has a distinct Xi DNAme landscape, which may inform our understanding of sex differences during prenatal development. Future research should explore the mechanisms underlying the placenta's unique X-linked DNAme profile, and the factors involved in placental XCI maintenance.
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http://dx.doi.org/10.1186/s13293-025-00696-6 | DOI Listing |
Nat Genet
September 2025
Institut Curie, PSL Research University, Sorbonne Université, CNRS, UMR144 and UMR3664, Paris, France.
Maintaining the epigenetic identity of centromeres is essential to prevent genome instability. Centromeres are epigenetically defined by the histone H3 variant CENP-A. Prior work in human centromeres has shown that CENP-A is associated with regions of hypomethylated DNA located within large arrays of hypermethylated repeats, but the functional importance of these DNA methylation (DNAme) patterns remains poorly understood.
View Article and Find Full Text PDFDev Cell
August 2025
Friedrich Miescher Institute for Biomedical Research, 4056 Basel, Switzerland; Faculty of Sciences, University of Basel, 4056 Basel, Switzerland. Electronic address:
Except for regulatory CpG-island sequences, genomes of most mammalian cells are widely DNA-methylated. In oocytes, though, DNA methylation (DNAme) is largely confined to transcribed regions. The mechanisms restricting de novo DNAme in oocytes and their relevance thereof for zygotic genome activation and embryonic development are largely unknown.
View Article and Find Full Text PDFSci Rep
August 2025
Department of Immunology, Genetics and Pathology, Rudbeck Laboratory, Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
Unlabelled: Comprehensive epigenomic studies in multiple myeloma (MM) that unravel the connections between major epigenetic regulators, their intertwined collaboration and the potential of combinatorial targeting remain limited. Utilizing ChIP-seq, ATAC-seq, RNA-seq, and DNA methylation (DNAme) data, we generated whole-genome chromatin annotations from normal plasma cells and MM patients, revealing epigenomic re-configuration affecting downstream genes involved in tumour growth and survival. Primary MM samples showed global DNA hypomethylation but site-specific hypermethylation was observed at transcription start sites, promoters, and enhancers.
View Article and Find Full Text PDFCancer Epidemiol Biomarkers Prev
August 2025
University of Miami, Miami, United States.
Background: Social adversity from neighborhood disadvantage (ND) is associated with shorter breast cancer (BCa)-survival (BCSS). Although studies have identified associations between ND and DNA methylation (DNAme) or gene expression (mRNA), a study integrating DNAme and mRNA to understand how the epigenome regulates key biological pathways in ND, merits further inquiry.
Methods: DNAme, mRNA, miRNA, and tRNA-derived fragment data were analyzed from 80 ER+/HER2- BCa samples.
Clin Epigenetics
July 2025
Laboratory Genetic Metabolic Diseases, Amsterdam UMC Location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands.
Background: The 2021 Aging Report of the European Union projected significant increases in healthcare costs, with some member states expecting up to a 60% rise over the next 50 years, primarily due to an aging population and related diseases. Interventions targeting aging have been proposed to reduce this burden by extending healthspan. Recent evidence suggests that vegan diets may slow the aging process.
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