Journal Article

Control of <i>Xist</i> expression for imprinted and random X chromosome inactivation in mice

Junko Matsui, Yuji Goto and Nobuo Takagi

in Human Molecular Genetics

Volume 10, issue 13, pages 1393-1401
Published in print June 2001 | ISSN: 0964-6906
Published online June 2001 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/10.13.1393
Control of Xist expression for imprinted and random X chromosome inactivation in mice

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Applying RNA fluorescence in situ hybridization to parthenogenetic embryos with two maternally derived X (XM) chromosomes and embryos with X chromosome aneuploidy such as XP0 (XP, paternally derived X chromosome), XMXMXP and XMXMY, we studied the control of Xist/Tsix expression for silencing the entire X chromosome in mice. The data show that the paternally derived Xist allele is highly expressed in every cell of the embryo from the 4-cell stage onward, irrespective of the number of X chromosomes in a diploid cell. The high level of Xist transcription is maintained in non-epiblast cells culminating in XP-inactivation, whereas in XP0 embryos it is terminated by the blastocyst stage, probably as a result of counting the number of X chromosomes in a cell occurring at the morula/blastocyst stage. Xist is also down-regulated in epiblast cells of XMXP and XMXMXP embryos to make X-inactivation random. In epiblast cells, Xist seems to be up-regulated after counting and random choice of the future inactive X chromosome(s). Although the maternal Xist allele is never activated in fertilized embryos before implantation, some parthenogenetic embryos show Xist up-regulation in a proportion of cells. These and other data reported earlier suggest that imprinted X-inactivation in non-epiblast tissues of rodents had been derived from the random X-inactivation system.

Journal Article.  6462 words.  Illustrated.

Subjects: Genetics and Genomics

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