![]() In this study, we intended to find any conserved elements surrounding Xist in rodents (mouse, rat, and common voles). However, these regulatory elements have not been definitely identified in other eutherians. As is demonstrated, these elements in mice regulate Xist expression during imprinted and random XCIs and are involved in the mechanisms underlying the counting of X chromosome number per diploid set of autosomes and the choice of the X chromosome to be inactivated during random XCI. The microsatellite region DXPas34, the Tsix gene (the antisense counterpart to Xist), regulatory element Xite, and а 37 kb bipartite counting element have been mapped 3′ to Xist (reviewed in, ). Both genes are positive regulators of Xist. ![]() Two non-coding nuclear RNA genes Enox (Jpx) and Ftx are localized 5′ to Xist. ![]() The studies of the Xic in mice have detected multiple elements in surrounding Xist with roles at different stages of XCI. This is the only functional element of the Xic that has been identified in all eutherians studied –. It has been shown that the initiation of XCI and propagation of silencing are mainly provided by the Xist gene which produces a 17 kb nuclear RNA associated with the inactive X chromosome –. Random XCI takes place on either the maternal or paternal X chromosomes after Xp is reactivated in the cells giving rise to the embryo proper.Ī complex X-linked locus termed the X-inactivation centre (Xic) governs both imprinted and random XCI (reviewed in ). Imprinted XCI occurs on the paternal X chromosome (Xp) in the preimplantation embryo of some eutherians (for example, rodents) and is further maintained in the placenta. X chromosome inactivation (XCI) is a developmentally regulated process, which results in heterochromatization and transcriptional silencing of one of the two X chromosomes in eutherian females. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. 11-04-00799-a and 11-04-00847a, ), the Program of the Russian Academy of Sciences "Molecular and Cellular Biology" ( ) and the Wellcome Trust (grant no. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.įunding: This work was supported by the Russian Foundation for Basic Research (grant no. Received: ApAccepted: JPublished: August 3, 2011Ĭopyright: © 2011 Shevchenko et al. Chadwick, Florida State University, United States of America (2011) Variability of Sequence Surrounding the Xist Gene in Rodents Suggests Taxon-Specific Regulation of X Chromosome Inactivation. Overall, our data show that not all the functional elements surrounding Xist in mice are well conserved even within rodents, thereby suggesting that the regulation of XCI may be at least partially taxon-specific.Ĭitation: Shevchenko AI, Malakhova AA, Elisaphenko EA, Mazurok NA, Nesterova TB, Brockdorff N, et al. Furthermore, we have not identified any transcription that could have the same functions as murine Xite in voles. Most surprisingly, we have found that voles lack the regions homologous to the regulatory element Xite, which is instead replaced with the Slc7a3 gene that is unassociated with the X-inactivation centre in any other eutherians studied. A conservation of Tsix expression pattern in voles, rat and mice suggests a crucial role of the antisense transcription in regulation of Xist and XIC in rodents. We have also shown that in voles and rat the region homologous to the mouse Tsix major promoter, initiates antisense to Xist transcription and terminates around the Xist gene start site as is observed with mouse Tsix. We have found that mouse regions of the Tsix gene major promoter and minisatellite repeat DXPas34 are conserved among rodents. In this study, we examined in rodents (voles and rat) the conservation of the microsatellite region DXPas34, the Tsix gene (antisense counterpart of Xist), and enhancer Xite that have been shown to flank Xist and regulate XCI in mouse. One of the two X chromosomes in female mammalian cells is subject to inactivation (XCI) initiated by the Xist gene.
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