Journal articles: 'X-chromosome inactivation'

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Cattanach, Bruce M., and Colin V. Beechey. "Autosomal and X-chromosome imprinting." Development 108, Supplement (April 1, 1990): 63–72. http://dx.doi.org/10.1242/dev.108.supplement.63.

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Mouse genetic studies using Robertsonian and reciprocal translations have shown that certain autosomal regions of loci are subject to a parental germ line imprint, which renders maternal and paternal copies functionally inequivalent in the embryo or later stages of development. Duplication of maternal or paternal copies with corresponding paternal/maternal deficiencies in chromosomally balanced zygotes causes various effects. These range from early embryonic lethalities through to mid-fetal and neonatal lethalities, and in some instances viable young with phenotypic effects are obtained. Eight to nine chromosomal regions that give such imprinting effects have been identified. Six to seven of these regions are located in only three chromosomes (2, 7 and 17). The two other regions are located in chromosomes 6 and 11. Maternal and paternal disomies for each of four other chromosomes (1, 5, 9 and 14) have been recovered with different frequencies, but the possibility that this may be due to imprinting has yet to be supported by follow-up studies on regions of the chromosomes concerned. No clear evidence of genetic-background modifications of the imprinting process have been observed in these mouse genetic experiments. The mammalian X chromosome is also subject to imprinting, as demonstrated by the non-random, paternal X-inactivation in female mouse extra-embryonic tissues and in the somatic cells of marsupial females. There is also the opposite bias towards inactivation of the maternal X in the somatic cells of female mice. On the basis that both X-chromosome inactivation and autosomal chromosome imprinting may be concerned with gene regulation, it is suggested that evidence from X-chromosome inactivation studies may help to elucidate factors underlying the imprinting of autosomes. The relevant aspects of X-inactivation are summarized.

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Sado, Takashi, and Takehisa Sakaguchi. "Species-specific differences in X chromosome inactivation in mammals." REPRODUCTION 146, no. 4 (October 2013): R131—R139. http://dx.doi.org/10.1530/rep-13-0173.

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In female mammals, the dosage difference in X-linked genes between XX females and XY males is compensated for by inactivating one of the two X chromosomes during early development. Since the discovery of the X inactive-specific transcript (XIST) gene in humans and its subsequent isolation of the mouse homolog, Xist, in the early 1990s, the molecular basis of X chromosome inactivation (X-inactivation) has been more fully elucidated using genetically manipulated mouse embryos and embryonic stem cells. Studies on X-inactivation in other mammals, although limited when compared with those in the mice, have revealed that, while their inactive X chromosome shares many features with those in the mice, there are marked differences in not only some epigenetic modifications of the inactive X chromosome but also when and how X-inactivation is initiated during early embryonic development. Such differences raise the issue about what extent of the molecular basis of X-inactivation in the mice is commonly shared among others. Recognizing similarities and differences in X-inactivation among mammals may provide further insight into our understanding of not only the evolutionary but also the molecular aspects for the mechanism of X-inactivation. Here, we reviewed species-specific differences in X-inactivation and discussed what these differences may reveal.

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Rastan, Sohaila, and Elizabeth J. Robertson. "X-chromosome deletions in embryo-derived (EK) cell lines associated with lack of X-chromosome inactivation." Development 90, no. 1 (December 1, 1985): 379–88. http://dx.doi.org/10.1242/dev.90.1.379.

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The predictions of a model for the initiation of X-chromosome inactivation based on a single inactivation centre were tested in a cytogenetic study using six different embryo-derived (EK) stem cell lines, each with a different-sized deletion of the distal part of one of the X-chromosomes. Metaphase chromosomes were prepared by the Kanda method from each cell line in the undifferentiated state and after induction of differentiation, and cytogenetic evidence sought for a dark-staining inactive X-chromosome. The results confirm the predictions of the model in that when the inactivation centre is deleted from one of the X-chromosomes neither X present in a diploid cell can be inactivated, and in addition considerably further localize the position of the inactivation centre on the X-chromosome.

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Migeon, Barbara R. "X chromosome inactivation." Genome 31, no. 1 (January 1, 1989): 464. http://dx.doi.org/10.1139/g89-083.

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Lyon, Mary F. "X-chromosome inactivation." Current Biology 9, no. 7 (April 1999): R235—R237. http://dx.doi.org/10.1016/s0960-9822(99)80151-1.

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Malcore, Rebecca M., and Sundeep Kalantry. "A Comparative Analysis of Mouse Imprinted and Random X-Chromosome Inactivation." Epigenomes 8, no. 1 (February 10, 2024): 8. http://dx.doi.org/10.3390/epigenomes8010008.

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The mammalian sexes are distinguished by the X and Y chromosomes. Whereas males harbor one X and one Y chromosome, females harbor two X chromosomes. To equalize X-linked gene expression between the sexes, therian mammals have evolved X-chromosome inactivation as a dosage compensation mechanism. During X-inactivation, most genes on one of the two X chromosomes in females are transcriptionally silenced, thus equalizing X-linked gene expression between the sexes. Two forms of X-inactivation characterize eutherian mammals, imprinted and random. Imprinted X-inactivation is defined by the exclusive inactivation of the paternal X chromosome in all cells, whereas random X-inactivation results in the silencing of genes on either the paternal or maternal X chromosome in individual cells. Both forms of X-inactivation have been studied intensively in the mouse model system, which undergoes both imprinted and random X-inactivation early in embryonic development. Stable imprinted and random X-inactivation requires the induction of the Xist long non-coding RNA. Following its induction, Xist RNA recruits proteins and complexes that silence genes on the inactive-X. In this review, we present a current understanding of the mechanisms of Xist RNA induction, and, separately, the establishment and maintenance of gene silencing on the inactive-X by Xist RNA during imprinted and random X-inactivation.

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Lyon, M. F. "X Chromosome Inactivation and Imprinting." Acta geneticae medicae et gemellologiae: twin research 45, no. 1-2 (April 1996): 85. http://dx.doi.org/10.1017/s0001566000001148.

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In contrast to the random inactivation of either maternal or paternal X-chromosome in the somatic cells of eutherian mammals, in marsupials the paternal X-chromosome is preferentially inactivated in all cells. Similar exclusively paternal X-inactivation occurs in two extraembryonic cell lineages of mice and rats. Thus, genetic imprinting is an important feature of X-inactivation. In embryonic development the initiation of X-inactivation is thought to occur through the X-inactivation centre, located on the X-Chromosome, and thus imprinting probably acts through this centre. A candidate gene for a role in the inactivation centre is Xist (X inactive specific transcript) which is expressed only from the inactive X-Chromosome. The expression of Xist in the mouse embryo is appropriate for it to be a cause rather than a consequence of inactivation. It appears before inactivation, and only the paternal allele is expressed in the extraembryonic lineages. In the germ cells also changes in X-chromosome activity are accompanied by changes in Xist expression. Studies of methylation of the Xist gene have shown that in male tissues where Xist is not active it is fully methylated, whereas in the female the allele on the active X-chromosome only is methylated. In male germ cells, where Xist is expressed, it is demethylated and the demethylation persists in mature spermatozoa. Thus a methylation difference in germ cells could possibly be the imprint. In androgenotes, with paternally derived chromosomes, Xist is expressed at the 4-cell stage, whereas in gynogenotes and parthenogenotes expression does not appear until the blastocyst stage. Thus, Xist expression shows imprinting. When expression appears in parthenogenotes it is random, suggesting that the imprint has been lost. The Xist gene has no open reading frame and is thought to act through mRNA but its function is unknown.

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Shevchenko, Alexander I., Elena V. Dementyeva, Irina S. Zakharova, and Suren M. Zakian. "Diverse developmental strategies of X chromosome dosage compensation in eutherian mammals." International Journal of Developmental Biology 63, no. 3-4-5 (2019): 223–33. http://dx.doi.org/10.1387/ijdb.180376as.

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In eutherian mammals, dosage compensation arose to balance X-linked gene expression between sexes and relatively to autosomal gene expression in the evolution of sex chromosomes. Dosage compensation occurs in early mammalian development and comprises X chromosome upregulation and inactivation that are tightly coordinated epigenetic processes. Despite a uniform principle of dosage compensation, mechanisms of X chromosome inactivation and upregulation demonstrate a significant variability depending on sex, developmental stage, cell type, individual, and mammalian species. The review focuses on relationships between X chromosome inactivation and upregulation in mammalian early development.

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Tukiainen, Taru, Alexandra-Chloé Villani, Angela Yen, Manuel A. Rivas, Jamie L. Marshall, Rahul Satija, Matt Aguirre, et al. "Landscape of X chromosome inactivation across human tissues." Nature 550, no. 7675 (October 12, 2017): 244–48. http://dx.doi.org/10.1038/nature24265.

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Abstract X chromosome inactivation (XCI) silences transcription from one of the two X chromosomes in female mammalian cells to balance expression dosage between XX females and XY males. XCI is, however, incomplete in humans: up to one-third of X-chromosomal genes are expressed from both the active and inactive X chromosomes (Xa and Xi, respectively) in female cells, with the degree of ‘escape’ from inactivation varying between genes and individuals1,2. The extent to which XCI is shared between cells and tissues remains poorly characterized3,4, as does the degree to which incomplete XCI manifests as detectable sex differences in gene expression5 and phenotypic traits6. Here we describe a systematic survey of XCI, integrating over 5,500 transcriptomes from 449 individuals spanning 29 tissues from GTEx (v6p release) and 940 single-cell transcriptomes, combined with genomic sequence data. We show that XCI at 683 X-chromosomal genes is generally uniform across human tissues, but identify examples of heterogeneity between tissues, individuals and cells. We show that incomplete XCI affects at least 23% of X-chromosomal genes, identify seven genes that escape XCI with support from multiple lines of evidence and demonstrate that escape from XCI results in sex biases in gene expression, establishing incomplete XCI as a mechanism that is likely to introduce phenotypic diversity6,7. Overall, this updated catalogue of XCI across human tissues helps to increase our understanding of the extent and impact of the incompleteness in the maintenance of XCI.

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Zlotorynski, Eytan. "X-chromosome inactivation unravelled." Nature Reviews Molecular Cell Biology 16, no. 6 (May 8, 2015): 325. http://dx.doi.org/10.1038/nrm3998.

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Rougeulle, Claire. "Inactivation du chromosome X." médecine/sciences 25, no. 3 (March 2009): 234–35. http://dx.doi.org/10.1051/medsci/2009253234.

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Zlotorynski, Eytan. "X chromosome inactivation unravelled." Nature Reviews Genetics 16, no. 6 (May 18, 2015): 315. http://dx.doi.org/10.1038/nrg3955.

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Augui, Sandrine, and Edith Heard. "Inactivation du chromosome X." médecine/sciences 24, no. 6-7 (June 2008): 584–85. http://dx.doi.org/10.1051/medsci/20082467584.

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Shevchenko, A. I., I. S. Zakharova, and S. M. Zakian. "The Evolutionary Pathway of X Chromosome Inactivation in Mammals." Acta Naturae 5, no. 2 (June 15, 2013): 40–53. http://dx.doi.org/10.32607/20758251-2013-5-2-40-53.

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X chromosome inactivation is a complex process that occurs in marsupial and eutherian mammals. The process is thought to have arisen during the differentiation of mammalian sex chromosomes to achieve an equal dosage of X chromosome genes in males and females. The differences in the X chromosome inactivation processes in marsupial and eutherian mammals are considered, and the hypotheses on its origin and evolution are discussed in this review.

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Viera, Alberto, María Teresa Parra, Sara Arévalo, Carlos García de la Vega, Juan Luis Santos, and Jesús Page. "X Chromosome Inactivation during Grasshopper Spermatogenesis." Genes 12, no. 12 (November 23, 2021): 1844. http://dx.doi.org/10.3390/genes12121844.

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Regulation of transcriptional activity during meiosis depends on the interrelated processes of recombination and synapsis. In eutherian mammal spermatocytes, transcription levels change during prophase-I, being low at the onset of meiosis but highly increased from pachytene up to the end of diplotene. However, X and Y chromosomes, which usually present unsynapsed regions throughout prophase-I in male meiosis, undergo a specific pattern of transcriptional inactivation. The interdependence of synapsis and transcription has mainly been studied in mammals, basically in mouse, but our knowledge in other unrelated phylogenetically species is more limited. To gain new insights on this issue, here we analyzed the relationship between synapsis and transcription in spermatocytes of the grasshopper Eyprepocnemis plorans. Autosomal chromosomes of this species achieve complete synapsis; however, the single X sex chromosome remains always unsynapsed and behaves as a univalent. We studied transcription in meiosis by immunolabeling with RNA polymerase II phosphorylated at serine 2 and found that whereas autosomes are active from leptotene up to diakinesis, the X chromosome is inactive throughout meiosis. This inactivation is accompanied by the accumulation of, at least, two repressive epigenetic modifications: H3 methylated at lysine 9 and H2AX phosphorylated at serine 139. Furthermore, we identified that X chromosome inactivation occurs in premeiotic spermatogonia. Overall, our results indicate: (i) transcription regulation in E. plorans spermatogenesis differs from the canonical pattern found in mammals and (ii) X chromosome inactivation is likely preceded by a process of heterochromatinization before the initiation of meiosis.

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Lyon, Mary F. "Do LINEs Have a Role in X-Chromosome Inactivation?" Journal of Biomedicine and Biotechnology 2006 (2006): 1–6. http://dx.doi.org/10.1155/jbb/2006/59746.

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There is longstanding evidence that X-chromosome inactivation (XCI) travels less successfully in autosomal than in X-chromosomal chromatin. The interspersed repeat elements LINE1s (L1s) have been suggested as candidates for “boosters” which promote the spread of XCI in the X-chromosome. The present paper reviews the current evidence concerning the possible role of L1s in XCI. Recent evidence, accruing from the human genome sequencing project and other sources, confirms that mammalian X-chromosomes are indeed rich in L1s, except in regions where there are many genes escaping XCI. The density of L1s is the highest in the evolutionarily oldest regions. Recent work on X; autosome translocations in human and mouse suggested failure of stabilization of XCI in autosomal material, so that genes are reactivated, but resistance of autosomal genes to the original silencing is not excluded. The accumulation of L1s on the X-chromosome may have resulted from reduced recombination or late replication. Whether L1s are part of the mechanism of XCI or a result of it remains enigmatic.

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Watson, JM. "Monotreme Genetics and Cytology and a Model for Sex-Chromosome Evolution." Australian Journal of Zoology 37, no. 3 (1989): 385. http://dx.doi.org/10.1071/zo9890385.

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The protherian mammals consist of three species: the platypus, the Australian echidna and the Niugini echidna. These mammals diverged from the therian line of descent about 150-200 million years ago; hence comparisons of gene arrangements and gene control mechanisms between prototherian and therian mammals may yield significant data about gene rearrangements during mammalian evolution and about the evolution of complex genetic control systems. The chromosome complements of the three monotreme species are highly conserved. In particular, the X (or X1) chromosomes are G-band identical and share considerable G-band homology with the Y chromosomes. Replication asynchrony between X chromosomes suggests that X chromosome inactivation operates in females, and is apparently tissue- specific (as it is in marsupials), and confined to the differential region of the X (X1) chromosome (as it is in eutherian mammals). These results suggest that sex chromosome differentiation in the monotremes represents an intermediate stage in the evolution of the dimorphic sex chromosomes of therian mammals and that X-chromosome inactivation may also represent a comparatively primitive stage. Studies of gene location in the platypus using platypus-rodent cell hybrids suggested that HPRT and PGK are syntenic in the platypus, but it was not possible to assign the syntenic group to a particular chromosome. In situ hybridisation was used to assign three genes, located on the X in eutherians and marsupials, to the monotreme X. However, human X short-arm markers were found by in situ hybridisation to be autosomal in monotremes (as they are in marsupials). A model for the evolution of mammalian sex chromosome differentiation and X-chromosome inactivation is presented in which a gradual reduction of the Y chromosome, and recruitment of newly unpaired loci on the X into a system of X-chromosome inactivation, has accompanied eutherian evolution.

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Monk, Marilyn, and Mark Grant. "Preferential X-chromosome inactivation, DNA methylation and imprinting." Development 108, Supplement (April 1, 1990): 55–62. http://dx.doi.org/10.1242/dev.108.supplement.55.

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Non-random X-chromosome inactivation in mammals was one of the first observed examples of differential expression dependent on the gamete of origin of the genetic material. The paternally-inherited X chromosome is preferentially inactive in all cells of female marsupials and in the extra-embryonic tissues of developing female rodents. Some form of parental imprinting during male and female gametogenesis must provide a recognition signal that determines the nonrandomness of X-inactivation but its nature is thus far unknown. In the mouse, the imprint distinguishing the X chromosomes in the extra-embryonic tissues must be erased early in development since X-inactivation is random in the embryonic cells. Random X-chromosome inactivation leads to cellular mosaicism in expression and differential methylation of active and inactive X-linked genes. Transgene imprinting shares many features with X-inactivation, including differential DNA methylation. In this paper we consider when methylation differences in early development affecting X-chromosome activity and imprinting are established. There are processes of methylation and demethylation occurring in early development, as well as changes in the activity of the DNA methylase itself. Methylation of a specific CpG site associated with activity of the X-linked PGK-1 gene has been studied. This site is already methylated on the inactive X chromosome by 6.5 days' gestation, close to the time of X-inactivation. However, differential methylation of this site is not the primary imprint marking the paternal X chromosome for preferential inactivation in the extra-embryonic membranes. A consideration of factors influencing both X-chromosome inactivation and imprinting suggests that a process of communication and comparison between nonidentical alleles might by the basis for the differential modification and expression patterns observed.

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SCIALDONE, ANTONIO, and MARIO NICODEMI. "STATISTICAL MECHANICS MODELS FOR X-CHROMOSOME INACTIVATION." Advances in Complex Systems 13, no. 03 (June 2010): 367–76. http://dx.doi.org/10.1142/s0219525910002566.

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We present statistical mechanics models to understand the physical and molecular mechanisms of X-Chromosome Inactivation (XCI), the process whereby a female mammal cell inactivates one of its two X-chromosomes. During XCI, X-chromosomes undergo a series of complex regulatory processes. At the beginning of XCI, the X's recognize and pair, then only one X which is randomly chosen is inactivated. Afterwards, the two X's move to different positions in the cell nucleus according to their different status (active/silenced). Our models illustrate about the still mysterious physical bases underlying all these regulatory steps, i.e., X-chromosome pairing, random choice of inactive X, and "shuttling" of the X's to their post-XCI locations. Our models are based on general and robust thermodynamic roots, and their validity can go beyond XCI, to explain analogous regulatory mechanisms in a variety of cellular processes.

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Clemson, Christine Moulton, Jennifer C. Chow, Carolyn J. Brown, and Jeanne Bentley Lawrence. "Stabilization and Localization of Xist RNA are Controlled by Separate Mechanisms and are Not Sufficient for X Inactivation." Journal of Cell Biology 142, no. 1 (July 13, 1998): 13–23. http://dx.doi.org/10.1083/jcb.142.1.13.

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These studies address whether XIST RNA is properly localized to the X chromosome in somatic cells where human XIST expression is reactivated, but fails to result in X inactivation (Tinker, A.V., and C.J. Brown. 1998. Nucl. Acids Res. 26:2935–2940). Despite a nuclear RNA accumulation of normal abundance and stability, XIST RNA does not localize in reactivants or in naturally inactive human X chromosomes in mouse/ human hybrid cells. The XIST transcripts are fully stabilized despite their inability to localize, and hence XIST RNA localization can be uncoupled from stabilization, indicating that these are separate steps controlled by distinct mechanisms. Mouse Xist RNA tightly localized to an active X chromosome, demonstrating for the first time that the active X chromosome in somatic cells is competent to associate with Xist RNA. These results imply that species-specific factors, present even in mature, somatic cells that do not normally express Xist, are necessary for localization. When Xist RNA is properly localized to an active mouse X chromosome, X inactivation does not result. Therefore, there is not a strict correlation between Xist localization and chromatin inactivation. Moreover, expression, stabilization, and localization of Xist RNA are not sufficient for X inactivation. We hypothesize that chromosomal association of XIST RNA may initiate subsequent developmental events required to enact transcriptional silencing.

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Lu, Zhipeng, Ava C. Carter, and Howard Y. Chang. "Mechanistic insights in X-chromosome inactivation." Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1733 (September 25, 2017): 20160356. http://dx.doi.org/10.1098/rstb.2016.0356.

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X-chromosome inactivation (XCI) is a critical epigenetic mechanism for balancing gene dosage between XY males and XX females in eutherian mammals. A long non-coding RNA (lncRNA), XIST, and its associated proteins orchestrate this multi-step process, resulting in the inheritable silencing of one of the two X-chromosomes in females. The XIST RNA is large and complex, exemplifying the unique challenges associated with the structural and functional analysis of lncRNAs. Recent technological advances in the analysis of macromolecular structure and interactions have enabled us to systematically dissect the XIST ribonucleoprotein complex, which is larger than the ribosome, and its place of action, the inactive X-chromosome. These studies shed light on key mechanisms of XCI, such as XIST coating of the X-chromosome, recruitment of DNA, RNA and histone modification enzymes, and compaction and compartmentalization of the inactive X. Here, we summarize recent studies on XCI, highlight the critical contributions of new technologies and propose a unifying model for XIST function in XCI where modular domains serve as the structural and functional units in both lncRNA–protein complexes and DNA–protein complexes in chromatin. This article is part of the themed issue ‘X-chromosome inactivation: a tribute to Mary Lyon’.

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Cooper, DW, PG Johnston, JL Vandeberg, and ES Robinson. "X-Chromosome Inactivation in Marsupials." Australian Journal of Zoology 37, no. 3 (1989): 411. http://dx.doi.org/10.1071/zo9890411.

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Marsupial (metatherian) mammals resemble their eutherian ('placental') counterparts in having inacti- vation of one of the two X chromosomes in the soma and premeiotic germ cells of their females. The marsupial X-inactivation system differs from the eutherian system in two respects: firstly, inactivation occurs for the paternally derived allele, i.e. it is not random, and secondly it is often incomplete. Data are available for four X-linked loci, all controlling enzyme structure: glucose-6- phosphate dehydrogenase (G6PD), phosphoglycerate kinase 1 (PGKl), alpha-galactosidase (GLA) and hypoxanthine phosphoribosyl transferase (HPRT). Both the G6PD and PGKl loci exhibit incomplete X-chromosome inactivation. The pattern of partial expression differs from tissue to tissue and from species to species. One of the two X chromosomes exhibits late replication, even in cells where a paternally derived gene is partly active, showing that late replication and absence of transcription are not completely correlated. Sex chromatin bodies are not as easily found as in some eutherians. In marsupials they are most clearly demonstrable in species with small Y chromosomes. Investigations into X-inactivation in early development have just begun. Absence of inactivation at the G6PD locus in yolk sac of a kangaroo has been observed. All other tissues exhibited complete paternal X-inacti- vation for G6PD. In a dasyurid, GLA showed complete paternal X-inactivation in all embryonic and extra-embryonic tissues. The role, if any, of methylation of cytosine residues in CpG pairs in the maintenance of X-inactivation in marsupials is unclear. Preliminary evidence indicates that sex-specific differences in methylation of sex linked genes do exist in marsupials.

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Goto, Tetsuya, and Marilyn Monk. "Regulation of X-Chromosome Inactivation in Development in Mice and Humans." Microbiology and Molecular Biology Reviews 62, no. 2 (June 1, 1998): 362–78. http://dx.doi.org/10.1128/mmbr.62.2.362-378.1998.

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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.

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Sarel-Gallily, Roni, and Nissim Benvenisty. "Large-Scale Analysis of X Inactivation Variations between Primed and Naïve Human Embryonic Stem Cells." Cells 11, no. 11 (May 24, 2022): 1729. http://dx.doi.org/10.3390/cells11111729.

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X chromosome inactivation is a mammalian dosage compensation mechanism, where one of two X chromosomes is randomly inactivated in female cells. Previous studies have suggested that primed human embryonic stem cells (hESCs) maintain an eroded state of the X chromosome and do not express XIST, while in naïve transition, both XIST and the eroded X chromosome are reactivated. However, the pattern of chromosome X reactivation in naïve hESCs remains mainly unknown. In this study, we examine the variations in the status of X chromosome between primed and naïve hESCs by analyzing RNA sequencing samples from different studies. We show that most samples of naïve hESCs indeed reactivate XIST and there is an increase in gene expression levels on chromosome X. However, most of the naïve samples do not fully activate chromosome X in a uniform manner and present a distinct eroded pattern, probably as a result of XIST reactivation and initiation of re-inactivation of chromosome X. This large-scale analysis provides a higher-resolution description of the changes occurring in chromosome X during primed-to-naïve transition and emphasizes the importance of taking these variations into consideration when studying X inactivation in embryonic development.

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Homolka, D., R. Ivanek, J. Capkova, P. Jansa, and J. Forejt. "Chromosomal rearrangement interferes with meiotic X chromosome inactivation." Genome Research 17, no. 10 (September 4, 2007): 1431–37. http://dx.doi.org/10.1101/gr.6520107.

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Furlan, Giulia, and Rafael Galupa. "Mechanisms of Choice in X-Chromosome Inactivation." Cells 11, no. 3 (February 3, 2022): 535. http://dx.doi.org/10.3390/cells11030535.

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Early in development, placental and marsupial mammals harbouring at least two X chromosomes per nucleus are faced with a choice that affects the rest of their lives: which of those X chromosomes to transcriptionally inactivate. This choice underlies phenotypical diversity in the composition of tissues and organs and in their response to the environment, and can determine whether an individual will be healthy or affected by an X-linked disease. Here, we review our current understanding of the process of choice during X-chromosome inactivation and its implications, focusing on the strategies evolved by different mammalian lineages and on the known and unknown molecular mechanisms and players involved.

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Tada, T., Y. Obata, M. Tada, Y. Goto, N. Nakatsuji, S. Tan, T. Kono, and N. Takagi. "Imprint switching for non-random X-chromosome inactivation during mouse oocyte growth." Development 127, no. 14 (July 15, 2000): 3101–5. http://dx.doi.org/10.1242/dev.127.14.3101.

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In mammals, X-chromosome inactivation occurs in all female cells, leaving only a single active X chromosome. This serves to equalise the dosage of X-linked genes in male and female cells. In the mouse, the paternally derived X chromosome (X(P)) is imprinted and preferentially inactivated in the extraembryonic tissues whereas in the embryonic tissues inactivation is random. To investigate how X(P) is chosen as an inactivated X chromosome in the extraembryonic cells, we have produced experimental embryos by serial nuclear transplantation from non-growing (ng) oocytes and fully grown (fg) oocytes, in which the X chromosomes are marked with (1) an X-linked lacZ reporter gene to assay X-chromosome activity, or (2) the Rb(X.9)6H translocation as a cytogenetic marker for studying replication timing. In the extraembryonic tissues of these ng/fg embryos, the maternal X chromosome (X(M)) derived from the ng oocyte was preferentially inactivated whereas that from the fg oocyte remained active. However, in the embryonic tissues, X inactivation was random. This suggests that (1) a maternal imprint is set on the X(M) during oocyte growth, (2) the maternal imprint serves to render the X(M) resistant to inactivation in the extraembryonic tissues and (3) the X(M) derived from an ng oocyte resembles a normal X(P).

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Debrand, E., C. Chureau, D. Arnaud, P. Avner, and E. Heard. "Functional Analysis of the DXPas34Locus, a 3′ Regulator of Xist Expression." Molecular and Cellular Biology 19, no. 12 (December 1, 1999): 8513–25. http://dx.doi.org/10.1128/mcb.19.12.8513.

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ABSTRACT X inactivation in female mammals is controlled by a key locus on the X chromosome, the X-inactivation center (Xic). The Xic controls the initiation and propagation of inactivation in cis. It also ensures that the correct number of X chromosomes undergo inactivation (counting) and determines which X chromosome becomes inactivated (choice). The Xist gene maps to the Xic region and is essential for the initiation of X inactivation in cis. Regulatory elements of X inactivation have been proposed to lie 3′ toXist. One such element, lying 15 kb downstream ofXist, is the DXPas34 locus, which was first identified as a result of its hypermethylation on the active X chromosome and the correlation of its methylation level with allelism at the X-controlling element (Xce), a locus known to affect choice. In this study, we have tested the potential function of theDXPas34 locus in Xist regulation and X-inactivation initiation by deleting it in the context of largeXist-containing yeast artificial chromosome transgenes. Deletion of DXPas34 eliminates both Xistexpression and antisense transcription present in this region in undifferentiated ES cells. It also leads to nonrandom inactivation of the deleted transgene upon differentiation. DXPas34 thus appears to be a critical regulator of Xist activity and X inactivation. The expression pattern of DXPas34 during early embryonic development, which we report here, further suggests that it could be implicated in the regulation of imprintedXist expression.

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Panova, A. V., E. D. Nekrasov, M. A. Lagarkova, S. L. Kiselev, and A. N. Bogomazova. "Late Replication of the Inactive X Chromosome Is Independent of the Compactness of Chromosome Territory in Human Pluripotent Stem Cells." Acta Naturae 5, no. 2 (June 15, 2013): 54–61. http://dx.doi.org/10.32607/20758251-2013-5-2-54-61.

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Dosage compensation of the X chromosomes in mammals is performed via the formation of facultative heterochromatin on extra X chromosomes in female somatic cells. Facultative heterochromatin of the inactivated X (Xi), as well as constitutive heterochromatin, replicates late during the S-phase. It is generally accepted that Xi is always more compact in the interphase nucleus. The dense chromosomal folding has been proposed to define the late replication of Xi. In contrast to mouse pluripotent stem cells (PSCs), the status of X chromosome inactivation in human PSCs may vary significantly. Fluorescence in situ hybridization with a whole X-chromosome-specific DNA probe revealed that late-replicating Xi may occupy either compact or dispersed territory in human PSCs. Thus, the late replication of the Xi does not depend on the compactness of chromosome territory in human PSCs. However, the Xi reactivation and the synchronization in the replication timing of X chromosomes upon reprogramming are necessarily accompanied by the expansion of X chromosome territory.

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de Hoon, B., Erik Splinter, B. Eussen, J. C. W. Douben, E. Rentmeester, M. van de Heijning, J. S. E. Laven, J. E. M. M. de Klein, J. Liebelt, and J. Gribnau. "X chromosome inactivation in a female carrier of a 1.28 Mb deletion encompassing the human X inactivation centre." Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1733 (September 25, 2017): 20160359. http://dx.doi.org/10.1098/rstb.2016.0359.

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X chromosome inactivation (XCI) is a mechanism specifically initiated in female cells to silence one X chromosome, thereby equalizing the dose of X-linked gene products between male and female cells. XCI is regulated by a locus on the X chromosome termed the X-inactivation centre (XIC). Located within the XIC is XIST , which acts as a master regulator of XCI. During XCI, XIST is upregulated on the inactive X chromosome and chromosome-wide cis spreading of XIST leads to inactivation. In mouse, the Xic comprises Xist and all cis -regulatory elements and genes involved in Xist regulation. The activity of the XIC is regulated by trans -acting factors located elsewhere in the genome: X-encoded XCI activators positively regulating XCI, and autosomally encoded XCI inhibitors providing the threshold for XCI initiation. Whether human XCI is regulated through a similar mechanism, involving trans -regulatory factors acting on the XIC has remained elusive so far. Here, we describe a female individual with ovarian dysgenesis and a small X chromosomal deletion of the XIC. SNP-array and targeted locus amplification (TLA) analysis defined the deletion to a 1.28 megabase region, including XIST and all elements and genes that perform cis -regulatory functions in mouse XCI. Cells carrying this deletion still initiate XCI on the unaffected X chromosome, indicating that XCI can be initiated in the presence of only one XIC. Our results indicate that the trans -acting factors required for XCI initiation are located outside the deletion, providing evidence that the regulatory mechanisms of XCI are conserved between mouse and human. This article is part of the themed issue ‘X-chromosome inactivation: a tribute to Mary Lyon’.

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Heard, Edith, and Claire Rougeulle. "Digging into X chromosome inactivation." Science 374, no. 6570 (November 19, 2021): 942–43. http://dx.doi.org/10.1126/science.abm1857.

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Chang, Samuel, C. "Mechanisms of X-chromosome inactivation." Frontiers in Bioscience 11, no. 1 (2006): 852. http://dx.doi.org/10.2741/1842.

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Kay, Graham F. "Xist and X chromosome inactivation." Molecular and Cellular Endocrinology 140, no. 1-2 (May 1998): 71–76. http://dx.doi.org/10.1016/s0303-7207(98)00032-x.

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Brooks, Wesley H. "X Chromosome Inactivation and Autoimmunity." Clinical Reviews in Allergy & Immunology 39, no. 1 (August 4, 2009): 20–29. http://dx.doi.org/10.1007/s12016-009-8167-5.

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DISTECHE, CHRISTINE M., and JOEL B. BERLETCH. "X-chromosome inactivation and escape." Journal of Genetics 94, no. 4 (November 18, 2015): 591–99. http://dx.doi.org/10.1007/s12041-015-0574-1.

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Heard, Edith, Philippe Clerc, and Philip Avner. "X-CHROMOSOME INACTIVATION IN MAMMALS." Annual Review of Genetics 31, no. 1 (December 1997): 571–610. http://dx.doi.org/10.1146/annurev.genet.31.1.571.

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Liehr, Thomas, Monika Ziegler, Sharon Löhmer, and Anja Weise. "Assessing Skewed X-Chromosome Inactivation." Current Protocols in Human Genetics 98, no. 1 (July 2018): e66. http://dx.doi.org/10.1002/cphg.66.

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McBurney, Michael W. "X chromosome inactivation: A hypothesis." BioEssays 9, no. 2-3 (August 1988): 85–88. http://dx.doi.org/10.1002/bies.950090211.

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Rougeulle, Claire, Julie Chaumeil, Kavitha Sarma, C. David Allis, Danny Reinberg, Philip Avner, and Edith Heard. "Differential Histone H3 Lys-9 and Lys-27 Methylation Profiles on the X Chromosome." Molecular and Cellular Biology 24, no. 12 (June 15, 2004): 5475–84. http://dx.doi.org/10.1128/mcb.24.12.5475-5484.2004.

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ABSTRACT Histone H3 tail modifications are among the earliest chromatin changes in the X-chromosome inactivation process. In this study we investigated the relative profiles of two important repressive marks on the X chromosome: methylation of H3 lysine 9 (K9) and 27 (K27). We found that both H3K9 dimethylation and K27 trimethylation characterize the inactive X in somatic cells and that their relative kinetics of enrichment on the X chromosome as it undergoes inactivation are similar. However, dynamic changes of H3K9 and H3K27 methylation on the inactivating X chromosome compared to the rest of the genome are distinct, suggesting that these two modifications play complementary and perhaps nonredundant roles in the establishment and/or maintenance of X inactivation. Furthermore, we show that a hotspot of H3K9 dimethylation 5′ to Xist also displays high levels of H3 tri-meK27. However, analysis of this region in G9a mutant embryonic stem cells shows that these two methyl marks are dependent on different histone methyltransferases.

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Augui, Sandrine, Elphège P. Nora, and Edith Heard. "Regulation of X-chromosome inactivation by the X-inactivation centre." Nature Reviews Genetics 12, no. 6 (May 18, 2011): 429–42. http://dx.doi.org/10.1038/nrg2987.

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Rastan, S., and S. D. M. Brown. "The search for the mouse X-chromosome inactivation centre." Genetics Research 56, no. 2-3 (October 1990): 99–106. http://dx.doi.org/10.1017/s0016672300035163.

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SummaryThe phenomenon of X-chromosome inactivation in female mammals, whereby one of the two X chromosome present in each cell of the female embryo is inactivated early in development, was first described by Mary Lyon in 1961. Nearly 30 years later, the mechanism of X-chromosome inactivation remains unknown. Strong evidence has accumulated over the years, however, for the involvement of a major switch or inactivation centre on the mouse X chromosome. Identification of the inactivation centre at the molecular level would be an important step in understanding the mechanism of X-inactivation. In this paper we review the evidence for the existence and location of the X-inactivation centre on the mouse X-chromosome, present data on the molecular genetic mapping of this region, and describe ongoing strategies we are using to attempt to identify the inactivation centre at the molecular level.

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Lobo, Nunes, Gillis, Barros-Silva, Miranda-Gonçalves, Berg, Cantante, et al. "XIST-Promoter Demethylation as Tissue Biomarker for Testicular Germ Cell Tumors and Spermatogenesis Quality." Cancers 11, no. 9 (September 17, 2019): 1385. http://dx.doi.org/10.3390/cancers11091385.

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Background: The event of X chromosome inactivation induced by XIST, which is physiologically observed in females, is retained in testicular germ cell tumors (TGCTs), as a result of a supernumerary X chromosome constitution. X chromosome inactivation also occurs in male germline, specifically during spermatogenesis. We aimed to analyze the promoter methylation status of XIST in a series of TGCT tissues, representative cell lines, and testicular parenchyma. Methods: Two independent cohorts were included, comprising a total of 413 TGCT samples, four (T)GCT cell lines, and 86 testicular parenchyma samples. The relative amount of methylated and demethylated XIST promoter fragments was assessed by quantitative methylation-specific PCR (qMSP) and more sensitive high-resolution melting (HRM) methylation analyses. Results: Seminomas showed a lower amount of methylated XIST fragments as compared to non-seminomas or normal testis (p < 0.0001), allowing for a good discrimination among these groups (area under the curve 0.83 and 0.81, respectively). Seminomas showed a significantly higher content of demethylated XIST as compared to non-seminomas. The percentage of demethylated XIST fragment in cell lines reflected their chromosomal constitution (number of extra X chromosomes). A novel and strong positive correlation between the Johnsen’s score and XIST demethylation was identified (r = 0.75, p < 0.0001). Conclusions: The X chromosome inactivation event and demethylated XIST promoter are promising biomarkers for TGCTs and for assessing spermatogenesis quality.

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Jayaweera, Sanduni, Lakmal Gonawala, Nalaka Wijekoon, and Ranil de Silva. "Up to Date Discoveries of X Chromosome Inactivation in Humans Leading to Prospective Treatments for Chromosome-linked Disorders." International Journal of Biomedical Science 14, no. 2 (December 15, 2018): 48–56. http://dx.doi.org/10.59566/ijbs.2018.14048.

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Mammalian dosage compensation is a complex mechanism allowing inactivation of single X chromosome of the female to compensate to that of the X chromosome of the male. The mechanism includes many long non-coding RNA; mainly XIST, a noncoding RNA which coats the X chromosome to be inactivated and TSIX, another noncoding RNA act as a negative regulator of XIST preventing inactivation of the second X chromosome. Both XIST and TSIX and several other transcription factors along with polycomb proteins (PRC) work together in controlling the inactivation of one X chromosome while the other X chromosome remains active. This is facilitated by the sensing mechanism called the n-1 theory, induced by the X pairing region (XPR) allowing X chromosome pairing before inactivation. X inactivation occurs randomly and begins at the late blastocyst stage of an embryo when the cells start to differentiate by losing pluripotency. Therefore, pluripotent factors play an important role in inducing X chromosome inactivation. Once X chromosome is inactivated it is passed along cell division and maintained throughout life. This review discusses up-to-date discovered pathways involved in mammalian dosage compensation, from initiation to maintenance of the X chromosome inactivation and potential therapeutic effects for X chromosome-linked disorders.

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Chen, George L., and Josef T. Prchal. "X-linked clonality testing: interpretation and limitations." Blood 110, no. 5 (September 1, 2007): 1411–19. http://dx.doi.org/10.1182/blood-2006-09-018655.

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Abstract Clonality often defines the diseased state in hematology. Clonal cells are genetically homogenous and derived from the same precursor; their detection is based on genotype or phenotype. Genotypic clonality relies on somatic mutations to mark the clonal population. Phenotypic clonality identifies the clonal population by the expression pattern of surrogate genes that track the clonal process. The most commonly used phenotypic clonality methods are based on the X-chromosome inactivation principle. Clonality detection based on X-chromosome inactivation patterns (XCIP) requires discrimination of the active from the inactive X chromosome and differentiation of each X chromosome's parental origin. Detection methods are based on detection of X-chromosome sequence polymorphisms identified by protein isoforms, transcribed mRNA, and methylation status. Errors in interpreting clonality tests arise from stochastic, genetic, and cell selection pressures on the mechanism of X inactivation. Progressive X-chromosome skewing has recently been suggested by XCIP clonality studies in aging hematopoietic cells. This has led to new insights into the pathophysiology of X-linked and autoimmune disorders. Other research applications include combining XCIP clonality testing with genetic clonality testing to identify clonal populations with yet-to-be-discovered genetic changes.

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Basrur, P. K., L. E. L. Pinheiro, N. A. Berepubo, E. R. Reyes, and P. C. Popescu. "X chromosome inactivation in X autosome translocation carrier cows." Genome 35, no. 4 (August 1, 1992): 667–75. http://dx.doi.org/10.1139/g92-101.

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The pattern of X chromosome inactivation in X autosome translocation carriers in a herd of Limousin–Jersey crossbred cattle was studied using the reverse banding technique consisting of 5-bromodeoxyuridine incorporation and acridine orange staining and autoradiography on cultures of solid tissues and blood samples exposed to tritiated thymidine. The late-replicating X chromosome was noted to be the normal X in strikingly high proportions of cells in cultures of different tissues from all translocation carriers. It is suggested that the predominance of cells in which the normal X is inactivated may be the result of a postinactivation selection process. Such a selection process during the prenatal life favouring cells in which the genes of the normal X chromosome remain unexpressed in translocation carrier females may be the mechanism that helps these conceptuses escape the adverse effects of functional aneuploidy. Based on the observation that the translocation carriers of this line of cattle are exclusively females and that there is a higher than expected rate of pregnancy loss, it is also postulated that the altered X chromosome may be lethal to all male conceptuses and to some of their female counterparts.Key words: X inactivation, X autosome translocation, bovine chromosomes, familial translocation.

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Sahakyan, Anna, Kathrin Plath, and Claire Rougeulle. "Regulation of X-chromosome dosage compensation in human: mechanisms and model systems." Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1733 (September 25, 2017): 20160363. http://dx.doi.org/10.1098/rstb.2016.0363.

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The human blastocyst forms 5 days after one of the smallest human cells (the sperm) fertilizes one of the largest human cells (the egg). Depending on the sex-chromosome contribution from the sperm, the resulting embryo will either be female, with two X chromosomes (XX), or male, with an X and a Y chromosome (XY). In early development, one of the major differences between XX female and XY male embryos is the conserved process of X-chromosome inactivation (XCI), which compensates gene expression of the two female X chromosomes to match the dosage of the single X chromosome of males. Most of our understanding of the pre-XCI state and XCI establishment is based on mouse studies, but recent evidence from human pre-implantation embryo research suggests that many of the molecular steps defined in the mouse are not conserved in human. Here, we will discuss recent advances in understanding the control of X-chromosome dosage compensation in early human embryonic development and compare it to that of the mouse. This article is part of the themed issue ‘X-chromosome inactivation: a tribute to Mary Lyon’.

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Galupa, Rafael, and Edith Heard. "X-Chromosome Inactivation: A Crossroads Between Chromosome Architecture and Gene Regulation." Annual Review of Genetics 52, no. 1 (November 23, 2018): 535–66. http://dx.doi.org/10.1146/annurev-genet-120116-024611.

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In somatic nuclei of female therian mammals, the two X chromosomes display very different chromatin states: One X is typically euchromatic and transcriptionally active, and the other is mostly silent and forms a cytologically detectable heterochromatic structure termed the Barr body. These differences, which arise during female development as a result of X-chromosome inactivation (XCI), have been the focus of research for many decades. Initial approaches to define the structure of the inactive X chromosome (Xi) and its relationship to gene expression mainly involved microscopy-based approaches. More recently, with the advent of genomic techniques such as chromosome conformation capture, molecular details of the structure and expression of the Xi have been revealed. Here, we review our current knowledge of the 3D organization of the mammalian X-chromosome chromatin and discuss its relationship with gene activity in light of the initiation, spreading, and maintenance of XCI, as well as escape from gene silencing.

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Sado, Takashi, and Neil Brockdorff. "Advances in understanding chromosome silencing by the long non-coding RNA Xist." Philosophical Transactions of the Royal Society B: Biological Sciences 368, no. 1609 (January 5, 2013): 20110325. http://dx.doi.org/10.1098/rstb.2011.0325.

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In female mammals, one of the two X chromosomes becomes genetically silenced to compensate for dosage imbalance of X-linked genes between XX females and XY males. X chromosome inactivation (X-inactivation) is a classical model for epigenetic gene regulation in mammals and has been studied for half a century. In the last two decades, efforts have been focused on the X inactive-specific transcript ( Xist ) locus, discovered to be the master regulator of X-inactivation. The Xist gene produces a non-coding RNA that functions as the primary switch for X-inactivation, coating the X chromosome from which it is transcribed in cis . Significant progress has been made towards understanding how Xist is regulated at the onset of X-inactivation, but our understanding of the molecular basis of silencing mediated by Xist RNA has progressed more slowly. A picture has, however, begun to emerge, and new tools and resources hold out the promise of further advances to come. Here, we provide an overview of the current state of our knowledge, what is known about Xist RNA and how it may trigger chromosome silencing.

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O'Neill, Laura P., Hugh T. Spotswood, Milan Fernando, and Bryan M. Turner. "Differential loss of histone H3 isoforms mono-, di- and tri-methylated at lysine 4 during X-inactivation in female embryonic stem cells." Biological Chemistry 389, no. 4 (April 1, 2008): 365–70. http://dx.doi.org/10.1515/bc.2008.046.

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Abstract Silencing of genes on one of the two female X chromosomes early in development helps balance expression of X-linked genes between XX females and XY males and involves chromosome-wide changes in histone variants and modifications. Mouse female embryonic stem (ES) cells have two active Xs, one of which is silenced on differentiation, and provide a powerful model for studying the dynamics of X inactivation. Here, we use immunofluorescence microscopy of metaphase chromosomes to study changes in H3 mono-, di- or tri-methylated at lysine 4 (H3K4me1, -2 or -3) on the inactivating X (Xi) in female ES cells. H3K4me3 is absent from Xi in approximately 25% of chromosome spreads by day 2 of differentiation and in 40–50% of spreads by days 4–6, making it one of the earliest detectable changes on Xi. In contrast, loss of H3K4me2 occurs 1–2 days later, when histone acetylation also diminishes. Remarkably, H3K4me1 is depleted on both (active) X chromosomes in undifferentiated female ES cells, and on the single X in males, and remains depleted on Xi. Consistent with this, chromatin immunoprecipitation reveals differentiation-related reductions in H3K4me2 and H3K4me3 at the promoter regions of genes undergoing X-inactivation in female ES cells, but no comparable change in H3K4me1.

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Фонова, Е. А., Е. Н. Толмачева, А. А. Кашеварова, М. Е. Лопаткина, К. А. Павлова, and И. Н. Лебедев. "X-linked CNV and skewed X-chromosome inactivation." Nauchno-prakticheskii zhurnal «Medicinskaia genetika», no. 3() (March 30, 2020): 19–21. http://dx.doi.org/10.25557/2073-7998.2020.03.19-21.

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Смещение инактивации Х-хромосомы может быть следствием и маркером нарушения клеточной пролиферации при вариациях числа копий ДНК на Х-хромосоме. Х-сцепленные CNV выявляются как у женщин с невынашиванием беременности и смещением инактивации Х-хромосомы (с частотой 33,3%), так и у пациентов с умственной отсталостью и смещением инактивацией у их матерей (с частотой 40%). A skewed X-chromosome inactivation can be a consequence and a marker of impaired cell proliferation in the presence of copy number variations (CNV) on the X chromosome. X-linked CNVs are detected in women with miscarriages and a skewed X-chromosome inactivation (with a frequency of 33.3%), as well as in patients with intellectual disability and skewed X-chromosome inactivation in their mothers (with a frequency of 40%).

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Journal articles on the topic 'X-chromosome inactivation'

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