scholarly journals Induction of X-chromosome Inactivation by the Histone Demethylase SMCX/KDM5C

2017 ◽  
Author(s):  
Srimonta Gayen ◽  
Emily Maclary ◽  
Yumie Murata-Nakamura ◽  
Christina N. Vallianatos ◽  
Robert S. Porter ◽  
...  
Keyword(s):  
X Chromosome ◽  
Embryonic Stem ◽  
Histone Demethylase ◽  
X Inactivation ◽  
Linked Gene ◽  
Xist Rna ◽  
Evolutionarily Conserved ◽  
Specific Induction ◽  
Female Specific ◽  
Dose Dependent

SUMMARYXY male and XX female mammals equalize X-linked gene expression through the mitotically-stable transcriptional inactivation of an X-chromosome in females. Although most genes are silent on the inactive-X, some escape silencing and are expressed at higher levels in females vs. males. Here, we show that the escapee Smcx/Kdm5c, encoding a histone H3K4me2/3 demethylase, underlies the female-specific induction of X-inactivation. Mouse embryonic epiblast cells and differentiating embryonic stem cells (ESCs) lacking SMCX show reduced expression of Xist RNA, which is required for X-inactivation. Smcx-heterozygous epiblast cells do not silence X-linked genes efficiently, despite robust Xist expression. Overexpression of mouse or human SMCX, but not a catalytically-inactive SMCX or the Y-chromosome homolog SMCY, is sufficient to induce Xist and, separately, to silence X-linked genes in male ESCs. Finally, SMCX dose is inversely correlated with H3K4me2 at X-linked loci. Thus, X-inactivation initiates through the evolutionarily conserved, dose-dependent function of the histone demethylase SMCX.

scholarly journals Xmas ESC: A new female embryonic stem cell system that reveals the BAF complex as a key regulator of the establishment of X chromosome inactivation

2019 ◽  
Author(s):  
Andrew Keniry ◽  
Natasha Jansz ◽  
Linden J. Gearing ◽  
Iromi Wanigasuriya ◽  
Joseph Chen ◽  
...  
Keyword(s):  
X Chromosome ◽  
Embryonic Stem ◽  
X Chromosome Inactivation ◽  
Cell System ◽  
X Inactivation ◽  
Chromosome Inactivation ◽  
Baf Complex ◽  
Specific Process ◽  
Female Specific

SummaryAlthough female pluripotency significantly differs to male, complications with in vitro culture of female embryonic stem cells (ESC) have severely limited the use and study of these cells. We report a replenishable female ESC system, Xmas, that has enabled us to optimise a protocol for preserving the XX karyotype. Our protocol also improves male ESC fitness. We utilised our Xmas ESC system to screen for regulators of the female-specific process of X chromosome inactivation, revealing chromatin remodellers Smarcc1 and Smarca4 as key regulators of establishment of X inactivation. The remodellers create a nucleosome depleted region at gene promotors on the inactive X during exit from pluripotency, without which gene silencing fails. Our female ESC system provides a tractable model for XX ESC culture that will expedite study of female pluripotency and has enabled us to discover new features of the female-specific process of X inactivation.

scholarly journals Histone Macroh2a1.2 Relocates to the Inactive X Chromosome after Initiation and Propagation of X-Inactivation

1999 ◽  
Vol 147 (7) ◽  
pp. 1399-1408 ◽  
Author(s):  
Jacqueline E. Mermoud ◽  
Carl Costanzi ◽  
John R. Pehrson ◽  
Neil Brockdorff
Keyword(s):  
X Chromosome ◽  
Es Cells ◽  
Embryonic Stem ◽  
X Inactivation ◽  
Dense Region ◽  
Rich Domain ◽  
Inactive X Chromosome ◽  
Initiation And Propagation ◽  
Xist Rna

The histone macroH2A1.2 has been implicated in X chromosome inactivation on the basis of its accumulation on the inactive X chromosome (Xi) of adult female mammals. We have established the timing of macroH2A1.2 association with the Xi relative to the onset of X-inactivation in differentiating murine embryonic stem (ES) cells using immuno-RNA fluorescence in situ hybridization (FISH). Before X-inactivation we observe a single macroH2A1.2-dense region in both undifferentiated XX and XY ES cells that does not colocalize with X inactive specific transcript (Xist) RNA, and thus appears not to associate with the X chromosome(s). This pattern persists through early stages of differentiation, up to day 7. Then the frequency of XY cells containing a macroH2A1.2-rich domain declines. In contrast, in XX cells there is a striking relocalization of macroH2A1.2 to the Xi. Relocalization occurs in a highly synchronized wave over a 2-d period, indicating a precisely regulated association. The timing of macroH2A1.2 accumulation on the Xi suggests it is not necessary for the initiation or propagation of random X-inactivation.

scholarly journals Sex-specific silencing of X-linked genes by Xist RNA

2016 ◽  
Vol 113 (3) ◽  
pp. E309-E318 ◽  
Author(s):  
Srimonta Gayen ◽  
Emily Maclary ◽  
Michael Hinten ◽  
Sundeep Kalantry
Keyword(s):  
Stem Cells ◽  
Gene Silencing ◽  
X Chromosome ◽  
Noncoding Rna ◽  
Gene Dosage ◽  
Embryonic Stem ◽  
Linked Gene ◽  
Epiblast Stem Cells ◽  
Xist Rna ◽  
The Impact

X-inactive specific transcript (Xist) long noncoding RNA (lncRNA) is thought to catalyze silencing of X-linked genes in cis during X-chromosome inactivation, which equalizes X-linked gene dosage between male and female mammals. To test the impact of Xist RNA on X-linked gene silencing, we ectopically induced endogenous Xist by ablating the antisense repressor Tsix in mice. We find that ectopic Xist RNA induction and subsequent X-linked gene silencing is sex specific in embryos and in differentiating embryonic stem cells (ESCs) and epiblast stem cells (EpiSCs). A higher frequency of XΔTsixY male cells displayed ectopic Xist RNA coating compared with XΔTsixX female cells. This increase reflected the inability of XΔTsixY cells to efficiently silence X-linked genes compared with XΔTsixX cells, despite equivalent Xist RNA induction and coating. Silencing of genes on both Xs resulted in significantly reduced proliferation and increased cell death in XΔTsixX female cells relative to XΔTsixY male cells. Thus, whereas Xist RNA can inactivate the X chromosome in females it may not do so in males. We further found comparable silencing in differentiating XΔTsixY and 39,XΔTsix (XΔTsixO) ESCs, excluding the Y chromosome and instead implicating the X-chromosome dose as the source of the sex-specific differences. Because XΔTsixX female embryonic epiblast cells and EpiSCs harbor an inactivated X chromosome prior to ectopic inactivation of the active XΔTsix X chromosome, we propose that the increased expression of one or more X-inactivation escapees activates Xist and, separately, helps trigger X-linked gene silencing.

X-chromosome inactivation in XX androgenetic mouse embryos surviving implantation

Development ◽  
2000 ◽  
Vol 127 (19) ◽  
pp. 4137-4145 ◽  
Author(s):  
I. Okamoto ◽  
S. Tan ◽  
N. Takagi
Keyword(s):  
X Chromosome ◽  
Ectopic Expression ◽  
Blastocyst Stage ◽  
X Chromosome Inactivation ◽  
X Inactivation ◽  
Chromosome Inactivation ◽  
Current View ◽  
Replication Banding ◽  
Xist Rna ◽  
Morula Stage

Using genetic and cytogenetic markers, we assessed early development and X-chromosome inactivation (X-inactivation) in XX mouse androgenones produced by pronuclear transfer. Contrary to the current view, XX androgenones are capable of surviving to embryonic day 7.5, achieving basically random X-inactivation in all tissues including those derived from the trophectoderm and primitive endoderm that are characterized by paternal X-activation in fertilized embryos. This finding supports the hypothesis that in fertilized female embryos, the maternal X chromosome remains active until the blastocyst stage because of a rigid imprint that prevents inactivation, whereas the paternal X chromosome is preferentially inactivated in extra-embryonic tissues owing to lack of such imprint. In spite of random X-inactivation in XX androgenones, FISH analyses revealed expression of stable Xist RNA from every X chromosome in XX and XY androgenonetic embryos from the four-cell to morula stage. Although the occurrence of inappropriate X-inactivation was further suggested by the finding that Xist continues ectopic expression in a proportion of cells from XX and XY androgenones at the blastocyst and the early egg cylinder stage, a replication banding study failed to provide positive evidence for inappropriate X-inactivation at E6. 5.

Lack of inactivation of a mouse X-linked gene physically separated from the inactivation centre

Development ◽  
1986 ◽  
Vol 97 (1) ◽  
pp. 75-85
Author(s):  
Mary F. Lyon ◽  
J. Zenthon ◽  
E. P. Evans ◽  
M. D. Burtenshaw ◽  
Kathryn A. Wareham ◽  
...  
Keyword(s):  
X Chromosome ◽  
Normal Animal ◽  
Histochemical Staining ◽  
X Inactivation ◽  
Chromosome Break ◽  
Linked Gene ◽  
Short Product ◽  
Chromosome Segments ◽  
Harmful Effects

Previous evidence had shown that, when a mammalian X-chromosome is broken by a translocation, only one of the two X-chromosome segments shows cytological signs of X-inactivation in the form of late replication or Kanda staining. In the two mouse X-autosome translocations T(X;4)37H and T(X;11)38H the X-chromosome break is in the A1–A2 bands; in both, the shorter translocation product fails to exhibit Kanda staining. By in situ hybridization, the locus of ornithine carbamoyltransferase (OCT) was shown to be proximal to the breakpoint (i.e. on the short product) in T37H and distal to the breakpoint in T38H. Histochemical staining for OCT showed that in T38H the locus of OCT undergoes random inactivation, as in a chromosomally normal animal, whereas in T37H the OCT locus remains active in all cells. The interpretation is that, when a segment of X-chromosome is physically separated from the X-inactivation centre, it fails to undergo inactivation. This point is important for the understanding of the mechanism of X-inactivation, since it implies that inactivation is a positive process, brought about by some event that travels along the chromosome. It is also relevant to the interpretation of the harmful effects of X-autosome translocations and the abnormalities seen in individuals carrying such translocations.

Getting to the center of X-chromosome inactivation: the role of transgenesThis paper is one of a selection of papers published in this Special Issue, entitled 30th Annual International Asilomar Chromatin and Chromosomes Conference, and has undergone the Journal’s usual peer review process.

2009 ◽  
Vol 87 (5) ◽  
pp. 759-766 ◽  
Author(s):  
Jakub Minks ◽  
Carolyn J. Brown
Keyword(s):  
X Chromosome ◽  
Peer Review Process ◽  
Regulatory Elements ◽  
X Chromosome Inactivation ◽  
X Inactivation ◽  
Chromosome Inactivation ◽  
Xist Expression ◽  
Inactivation Center ◽  
Xist Rna ◽  
Epigenetic Phenomenon

X-chromosome inactivation is a fascinating epigenetic phenomenon that is initiated by expression of a noncoding (nc)RNA, XIST, and results in transcriptional silencing of 1 female X. The process requires a series of events that begins even before XIST expression, and culminates in an active and a silent X within the same nucleus. We will focus on the role that transgenic systems have served in the current understanding of the process of X-chromosome inactivation, both in the initial delineation of an active and inactive X, and in the function of the XIST RNA. X inactivation is strictly cis-limited; recent studies have revealed elements within the X-inactivation center, the region required for inactivation, that are critical for the initial regulation of Xist expression and chromosome pairing. It has been revealed that the X-inactivation center contains a remarkable compendium of cis-regulatory elements, ncRNAs, and trans-acting pairing regions. We review the functional componentry of the X-inactivation center and discuss experiments that helped to dissect the XIST/Xist RNA and its involvement in the establishment of facultative heterochromatin.

scholarly journals The dynamic epigenetic regulation of the inactive X chromosome in healthy human B cells is dysregulated in lupus patients

2021 ◽  
Vol 118 (24) ◽  
pp. e2024624118
Author(s):  
Sarah Pyfrom ◽  
Bam Paneru ◽  
James J. Knox ◽  
Michael P. Cancro ◽  
Sylvia Posso ◽  
...  
Keyword(s):  
Gene Expression ◽  
B Cells ◽  
B Cell ◽  
X Chromosome ◽  
Epigenetic Regulation ◽  
Healthy Human ◽  
Linked Gene ◽  
Xist Rna ◽  
B Cell Subsets ◽  
Human B Cell

Systemic lupus erythematous (SLE) is a female-predominant disease characterized by autoimmune B cells and pathogenic autoantibody production. Individuals with two or more X chromosomes are at increased risk for SLE, suggesting that X-linked genes contribute to the observed sex bias of this disease. To normalize X-linked gene expression between sexes, one X in female cells is randomly selected for transcriptional silencing through X-chromosome inactivation (XCI), resulting in allele-specific enrichment of epigenetic modifications, including histone methylation and the long noncoding RNA XIST/Xist on the inactive X (Xi). As we have previously shown that epigenetic regulation of the Xi in female lymphocytes from mice is unexpectedly dynamic, we used RNA fluorescence in situ hybridization and immunofluorescence to profile epigenetic features of the Xi at the single-cell level in human B cell subsets from pediatric and adult SLE patients and healthy controls. Our data reveal that abnormal XCI maintenance in B cells is a feature of SLE. Using single-cell and bulk-cell RNA sequencing datasets, we found that X-linked immunity genes escape XCI in specific healthy human B cell subsets and that human SLE B cells exhibit aberrant expression of X-linked genes and XIST RNA interactome genes. Our data reveal that mislocalized XIST RNA, coupled with a dramatic reduction in heterochromatic modifications at the Xi in SLE, predispose for aberrant X-linked gene expression from the Xi, thus defining a genetic and epigenetic pathway that affects X-linked gene expression in human SLE B cells and likely contributes to the female bias in SLE.

scholarly journals Elements at the 5′ end of Xist harbor SPEN-independent transcriptional antiterminator activity

2020 ◽  
Vol 48 (18) ◽  
pp. 10500-10517
Author(s):  
Jackson B Trotman ◽  
David M Lee ◽  
Rachel E Cherney ◽  
Susan O Kim ◽  
Kaoru Inoue ◽  
...  
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Gene Silencing ◽  
X Chromosome ◽  
Embryonic Stem ◽  
X Chromosome Inactivation ◽  
Xist Rna ◽  
Sequence Elements ◽  
Cleavage And Polyadenylation ◽  
Xist Locus

Abstract The Xist lncRNA requires Repeat A, a conserved RNA element located in its 5′ end, to induce gene silencing during X-chromosome inactivation. Intriguingly, Repeat A is also required for production of Xist. While silencing by Repeat A requires the protein SPEN, how Repeat A promotes Xist production remains unclear. We report that in mouse embryonic stem cells, expression of a transgene comprising the first two kilobases of Xist (Xist-2kb) causes transcriptional readthrough of downstream polyadenylation sequences. Readthrough required Repeat A and the ∼750 nucleotides downstream, did not require SPEN, and was attenuated by splicing. Despite associating with SPEN and chromatin, Xist-2kb did not robustly silence transcription, whereas a 5.5-kb Xist transgene robustly silenced transcription and read through its polyadenylation sequence. Longer, spliced Xist transgenes also induced robust silencing yet terminated efficiently. Thus, in contexts examined here, Xist requires sequence elements beyond its first two kilobases to robustly silence transcription, and the 5′ end of Xist harbors SPEN-independent transcriptional antiterminator activity that can repress proximal cleavage and polyadenylation. In endogenous contexts, this antiterminator activity may help produce full-length Xist RNA while rendering the Xist locus resistant to silencing by the same repressive complexes that the lncRNA recruits to other genes.

scholarly journals XistandTsixTranscription Dynamics Is Regulated by the X-to-Autosome Ratio and Semistable Transcriptional States

2016 ◽  
Vol 36 (21) ◽  
pp. 2656-2667 ◽  
Author(s):  
Friedemann Loos ◽  
Cheryl Maduro ◽  
Agnese Loda ◽  
Johannes Lehmann ◽  
Gert-Jan Kremers ◽  
...  
Keyword(s):  
X Chromosome ◽  
Gene Dosage ◽  
Embryonic Stem ◽  
Culture Conditions ◽  
Negative Regulator ◽  
Es Cell ◽  
Dynamic Regulation ◽  
Inactivation Center ◽  
Xist Rna ◽  
Central Elements

In female mammals, X chromosome inactivation (XCI) is a key process in the control of gene dosage compensation between X-linked genes and autosomes.XistandTsix, two overlapping antisense-transcribed noncoding genes, are central elements of the X inactivation center (Xic) regulating XCI.Xistupregulation results in the coating of the entire X chromosome by Xist RNA incis, whereasTsixtranscription acts as a negative regulator ofXist. Here, we generatedXistandTsixreporter mouse embryonic stem (ES) cell lines to study the genetic and dynamic regulation of these genes upon differentiation. Our results revealed mutually antagonistic roles forTsixonXistand vice versa and indicate the presence of semistable transcriptional states of theXiclocus predicting the outcome of XCI. These transcriptional states are instructed by the X-to-autosome ratio, directed by regulators of XCI, and can be modulated by tissue culture conditions.

Sign in / Sign up

Export Citation Format

Share Document