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Updated: Jul 28, 2025
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Combined DNA-RNA Fluorescent In situ Hybridization FISH to Study X Chromosome Inactivation in Differentiated Female Mouse Embryonic Stem Cells
Published on: June 14, 2014
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Refining the genomic determinants underlying escape from X-chromosome inactivation
Samantha Peeters1, Tiffany Leung1,2, Oriol Fornes1,2
1Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
NAR Genomics and Bioinformatics
|June 1, 2023
Summary
Female mammals silence one X chromosome via X-chromosome inactivation (XCI). Researchers identified gene promoter elements sufficient to drive escape from XCI, crucial for understanding gene expression differences and X aneuploidies.
Area of Science:
- Genetics
- Epigenetics
- Mammalian Biology
Background:
- X-chromosome inactivation (XCI) epigenetically silences one X chromosome in female mammals.
- While most X-linked genes are silenced, a significant portion (≥20% in humans) escape XCI, contributing to sex-based gene expression differences and X aneuploidy phenotypes.
- The regulatory mechanisms governing XCI escape remain largely unknown.
Purpose of the Study:
- To investigate the mechanisms regulating escape from X-chromosome inactivation (XCI).
- To identify transcription factors and regulatory elements involved in the expression of XCI escape genes.
Main Methods:
- Performed enrichment analysis of transcription factor binding sites on the X chromosome.
- Utilized a transgenic mouse model for targeted integration and inactivation of transgenes on the mouse X chromosome.
- Assessed promoter and genic elements of the RPS4X gene for their ability to drive XCI escape.
Main Results:
- Identified enriched transcription factors at the transcription start sites of XCI escape genes.
- Detected top escape-enriched transcription factors at the RPS4X promoter, a known human escape gene.
- A small transgenic construct (6 kb) containing RPS4X promoter and genic elements demonstrated robust escape from XCI.
- Established that gene-proximal elements are sufficient to permit XCI escape.
Conclusions:
- Gene-proximal elements are sufficient to drive escape from X-chromosome inactivation (XCI).
- Multiple elements can act additively in a context-specific manner to regulate XCI escape.
- Findings provide insights into the mechanisms of XCI escape and its potential impact on X aneuploidies.
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