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Federica Federici, Aristea Magaraki, Evelyne Wassenaar, Catherina J H van Veen-Buurman, Christine van de Werken, Esther B Baart, Joop S E Laven, J Anton Grootegoed, Joost Gribnau, Willy M Baarends
In mouse female preimplantation embryos, the paternal X chromosome (Xp) is silenced by imprinted X chromosome inactivation (iXCI). This requires production of the noncoding Xist RNA in cis, from the Xp. The Xist locus on the maternally inherited X chromosome (Xm) is refractory to activation due to the presence of an imprint. Paternal inheritance of an Xist deletion (XpΔXist) is embryonic lethal to female embryos, due to iXCI abolishment. Here, we circumvented the histone-to-protamine and protamine-to-histone transitions of the paternal genome, by fertilization of oocytes via injection of round spermatids (ROSI)...
October 2016: PLoS Genetics
Lin Yang, James E Kirby, Hongjae Sunwoo, Jeannie T Lee
X-chromosome inactivation (XCI) compensates for differences in X-chromosome number between male and female mammals. XCI is orchestrated by Xist RNA, whose expression in early development leads to transcriptional silencing of one X chromosome in the female. Knockout studies have established a requirement for Xist with inviability of female embryos that inherit an Xist deletion from the father. Here, we report that female mice lacking Xist RNA can, surprisingly, develop and survive to term. Xist-null females are born at lower frequency and are smaller at birth, but organogenesis is mostly normal...
August 1, 2016: Genes & Development
Friedemann Loos, Cheryl Maduro, Agnese Loda, Johannes Lehmann, Gert-Jan Kremers, Derk Ten Berge, J Anton Grootegoed, Joost Gribnau
In female mammals, X chromosome inactivation (XCI) is a key process in the control of gene dosage compensation between X-linked genes and autosomes. Xist and Tsix, two overlapping antisense-transcribed noncoding genes, are central elements of the X inactivation center (Xic) regulating XCI. Xist upregulation results in the coating of the entire X chromosome by Xist RNA in cis, whereas Tsix transcription acts as a negative regulator of Xist Here, we generated Xist and Tsix reporter mouse embryonic stem (ES) cell lines to study the genetic and dynamic regulation of these genes upon differentiation...
November 1, 2016: Molecular and Cellular Biology
Martina Rinčić, Ivan Y Iourov, Thomas Liehr
BACKGROUND: Chromosome counting is a process in which cells determine somehow their intrinsic chromosome number(s). The best-studied cellular mechanism that involves chromosome counting is 'chromosome-kissing' and X-chromosome inactivation (XCI) mechanism. It is necessary for the well-known dosage compensation between the genders in mammals to balance the number of active X-chromosomes (Xa) with regard to diploid set of autosomes. At the onset of XCI, two X-chromosomes are coming in close proximity and pair physically by a specific segment denominated X-pairing region (Xpr) that involves the SLC16A2 gene...
2016: Molecular Cytogenetics
Luca Giorgetti, Bryan R Lajoie, Ava C Carter, Mikael Attia, Ye Zhan, Jin Xu, Chong Jian Chen, Noam Kaplan, Howard Y Chang, Edith Heard, Job Dekker
X-chromosome inactivation (XCI) involves major reorganization of the X chromosome as it becomes silent and heterochromatic. During female mammalian development, XCI is triggered by upregulation of the non-coding Xist RNA from one of the two X chromosomes. Xist coats the chromosome in cis and induces silencing of almost all genes via its A-repeat region, although some genes (constitutive escapees) avoid silencing in most cell types, and others (facultative escapees) escape XCI only in specific contexts. A role for Xist in organizing the inactive X (Xi) chromosome has been proposed...
July 28, 2016: Nature
Pingyuan Xie, Qi Ouyang, Lizhi Leng, Liang Hu, Dehua Cheng, Yueqiu Tan, Guangxiu Lu, Ge Lin
X chromosome inactivation (XCI) is required for dosage compensation of X-linked genes in human female cells. Several previous reports have described the promiscuous XCI status in long-term cultured female human embryonic stem cells (hESCs), and the majority of them exhibit non-random XCI. However, when and how such female hESCs acquire the aberrant XCI states during culture is unknown. Herein, through comparing the XCI states in 18 paired hES cell lines throughout early culture, we revealed a uniform dynamic change during this culture period under a widely used culture condition...
July 2016: Stem Cell Research
Giulia Furlan, Claire Rougeulle
X-chromosome inactivation (XCI) is a chromosome-wide regulatory process that ensures dosage compensation for X-linked genes in Theria. XCI is established during early embryogenesis and is developmentally regulated. Different XCI strategies exist in mammalian infraclasses and the regulation of this process varies also among closely related species. In Eutheria, initiation of XCI is orchestrated by a cis-acting locus, the X-inactivation center (Xic), which is particularly enriched in genes producing long noncoding RNAs (lncRNAs)...
September 2016: Wiley Interdisciplinary Reviews. RNA
Hegias Mira-Bontenbal, Joost Gribnau
To achieve dosage compensation of X-linked gene expression, female mammalian cells inactivate one X chromosome through a process called X-chromosome inactivation (XCI). A central component of this process is the X-encoded long non-coding RNA Xist. Following upregulation from one X chromosome, Xist spreads in cis, kicking off a plethora of events that ultimately results in stable X-linked gene repression, which is then faithfully transmitted to all daughter cells. In the last decades, intensive work has been undertaken to understand each of the steps in XCI, namely Xist transcription control, Xist spreading and localization, and silencing of gene expression...
April 25, 2016: Current Biology: CB
Stefan F Pinter
Sex chromosomal dosage compensation in mammals takes the form of X chromosome inactivation (XCI), driven by the non-coding RNA Xist. In contrast to dosage compensation systems of flies and worms, mammalian XCI has to restrict its function to the Xist-producing X chromosome, while leaving autosomes and active X untouched. The mechanisms behind the long-range yet cis-specific localization and silencing activities of Xist have long been enigmatic, but genomics, proteomics, super-resolution microscopy, and innovative genetic approaches have produced significant new insights in recent years...
August 2016: Seminars in Cell & Developmental Biology
Amy Pandya-Jones, Kathrin Plath
The long non-coding RNA Xist directs a remarkable instance of developmentally regulated, epigenetic change known as X Chromosome Inactivation (XCI). By spreading in cis across the X chromosome from which it is expressed, Xist RNA facilitates the creation of a heritably silent, heterochromatic nuclear territory that displays a three-dimensional structure distinct from that of the active X chromosome. How Xist RNA attaches to and propagates across a chromosome and its influence over the three-dimensional (3D) structure of the inactive X are aspects of XCI that have remained largely unclear...
August 2016: Seminars in Cell & Developmental Biology
Jianle Wang, Camille M Syrett, Marianne C Kramer, Arindam Basu, Michael L Atchison, Montserrat C Anguera
Females have a greater immunological advantage than men, yet they are more prone to autoimmune disorders. The basis for this sex bias lies in the X chromosome, which contains many immunity-related genes. Female mammals use X chromosome inactivation (XCI) to generate a transcriptionally silent inactive X chromosome (Xi) enriched with heterochromatic modifications and XIST/Xist RNA, which equalizes gene expression between the sexes. Here, we examine the maintenance of XCI in lymphocytes from females in mice and humans...
April 5, 2016: Proceedings of the National Academy of Sciences of the United States of America
M Geens, A Seriola, L Barbé, J Santalo, A Veiga, K Dée, L Van Haute, K Sermon, C Spits
STUDY HYPOTHESIS: Does a preferential X chromosome inactivation (XCI) pattern exist in female human pluripotent stem cells (hPSCs) and does the pattern change during long-term culture or upon differentiation? STUDY FINDING: We identified two independent phenomena that lead to aberrant XCI patterns in female hPSC: a rapid loss of histone H3 lysine 27 trimethylation (H3K27me3) and long non-coding X-inactive specific transcript (XIST) expression during culture, often accompanied by erosion of XCI-specific methylation, and a frequent loss of random XCI in the cultures...
April 2016: Molecular Human Reproduction
Jean-François Ouimette, Claire Rougeulle
Genetic sex determination in mammals relies on dimorphic sex chromosomes that confer phenotypic/physiologic differences between males and females. In this heterogametic system, X and Y chromosomes diverged from an ancestral pair of autosomes, creating a genetic disequilibrium between XX females and XY males. Dosage compensation mechanisms alleviate intrinsic gene dosage imbalance, leading to equal expression levels of most X-linked genes in the two sexes. In therian mammals, this is achieved through inactivation of one of the two X chromosomes in females...
2016: Advances in Experimental Medicine and Biology
Jae Yeon Hwang, Jong-Nam Oh, Chi-Hun Park, Dong-Kyung Lee, Chang-Kyu Lee
X-chromosome inactivation (XCI) is an epigenetic mechanism that occurs in the eutherian embryo development to equalize the dosage of X-linked genes between males and females. This event is regulated by various factors, and the genes located in the X-chromosome inactivation center (XIC), which is known to be an evolutionary conserved region, are associated with XCI; however, a number of studies regarding this epigenetic event and genomic region are primarily performed in mouse models despite its species-specific features...
November 2015: Mechanisms of Development
Baohu Ji, Kerin K Higa, John R Kelsoe, Xianjin Zhou
BACKGROUND: Psychiatric disorders are common mental disorders without a pathological biomarker. Classic genetic studies found that an extra X chromosome frequently causes psychiatric symptoms in patients with either Klinefelter syndrome (XXY) or Triple X syndrome (XXX). Over-dosage of some X-linked escapee genes was suggested to cause psychiatric disorders. However, relevance of these rare genetic diseases to the pathogenesis of psychiatric disorders in the general population of psychiatric patients is unknown...
August 2015: EBioMedicine
Tatsuya Ohhata, Mika Matsumoto, Martin Leeb, Shinwa Shibata, Satoshi Sakai, Kyoko Kitagawa, Hiroyuki Niida, Masatoshi Kitagawa, Anton Wutz
One of the two X chromosomes in female mammals is inactivated by the noncoding Xist RNA. In mice, X chromosome inactivation (XCI) is regulated by the antisense RNA Tsix, which represses Xist on the active X chromosome. In the absence of Tsix, PRC2-mediated histone H3 lysine 27 trimethylation (H3K27me3) is established over the Xist promoter. Simultaneous disruption of Tsix and PRC2 leads to derepression of Xist and in turn silencing of the single X chromosome in male embryonic stem cells. Here, we identified histone H3 lysine 36 trimethylation (H3K36me3) as a modification that is recruited by Tsix cotranscriptionally and extends over the Xist promoter...
November 2015: Molecular and Cellular Biology
Jun Kang, Hee Jin Lee, Sun-Young Jun, Eun Su Park, Lee-So Maeng
BACKGROUND: Cancer-testis antigens (CTAs) are potential targets for cancer immunotherapy. Many CTAs are located on the X chromosome and are epigenetically regulated. Loss of X chromosome inactivation (XCI) is observed in breast and ovarian cancers and is thought to be related to the overexpression of CTAs. We investigated the relation between expression of CTAs and loss of XCI in endometrial cancer. MATERIALS AND METHODS: We used data generated by The Cancer Genome Atlas Genome Data Analysis Centers and data for Xist knockout mice available at the Gene Expression Omnibus...
2015: PloS One
Thomas Dixon-McDougall, Carolyn Brown
During X-chromosome inactivation (XCI), nearly an entire X chromosome is permanently silenced and converted into a Barr body, providing dosage compensation for eutherians between the sexes. XCI is facilitated by the upregulation of the long non-coding RNA gene, XIST, which coats its chromosome of origin, recruits heterochromatin factors, and silences gene expression. During XCI, at least two distinct types of heterochromatin are established, and in this review we discuss the enrichment of facultative heterochromatin marks such as H3K27me3, H2AK119ub, and macroH2A as well as pericentric heterochromatin marks such as HP1, H3K9me3, and H4K20me3...
February 2016: Biochemistry and Cell Biology, Biochimie et Biologie Cellulaire
Jae Yeon Hwang, Kwang-Hwan Choi, Dong-Kyung Lee, Seung-Hun Kim, Eun Bae Kim, Sang-Hwan Hyun, Chang-Kyu Lee
X-chromosome inactivation (XCI) is an epigenetic process that equalizes expression of X-borne genes between male and female eutherians. This process is observed in early eutherian embryo development in a species-specific manner. Until recently, various pluripotent factors have been suggested to regulate the process of XCI by repressing XIST expression, which is the master inducer for XCI. Recent insights into the process and its regulation have been restricted in mouse species despite the evolutionary diversity of the process and molecular mechanism among the species...
2015: Journal of Reproduction and Development
Joke G van Bemmel, Hegias Mira-Bontenbal, Joost Gribnau
Female mammalian cells compensate dosage of X-linked gene expression through the inactivation of one of their two X chromosomes. X chromosome inactivation (XCI) in eutherians is dependent on the non-coding RNA Xist that is up-regulated from the future inactive X chromosome, coating it and recruiting factors involved in silencing and altering its chromatin state. Xist lies within the X-inactivation center (Xic), a region on the X that is required for XCI, and is regulated in cis by elements on the X chromosome and in trans by diffusible factors...
March 2016: Chromosoma
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