Dataset Information

Revisiting the consequences of deleting the X inactivation center.

ABSTRACT: Mammalian cells equalize X-linked dosages between the male (XY) and female (XX) sexes by silencing one X chromosome in the female sex. This process, known as "X chromosome inactivation" (XCI), requires a master switch within the X inactivation center (Xic). The Xic spans several hundred kilobases in the mouse and includes a number of regulatory noncoding genes that produce functional transcripts. Over three decades, transgenic and deletional analyses have demonstrated both the necessity and sufficiency of the Xic to induce XCI, including the steps of X chromosome counting, choice, and initiation of whole-chromosome silencing. One recent study, however, reported that deleting the noncoding sequences of the Xic surprisingly had no effect for XCI and attributed a sufficiency to drive counting to the coding gene, Rnf12/Rlim Here, we revisit the question by creating independent Xic deletion cell lines. Multiple independent clones carrying heterozygous deletions of the Xic display an inability to up-regulate Xist expression, consistent with a counting defect. This defect is rescued by a second site mutation in Tsix occurring in trans, bypassing the defect in counting. These findings reaffirm the essential nature of noncoding Xic elements for the initiation of XCI.

SUBMITTER: Yin H

PROVIDER: S-EPMC8237661 | biostudies-literature | 2021 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Revisiting the consequences of deleting the X inactivation center.

Yin Hao H Wei Chunyao C Lee Jeannie T JT

Proceedings of the National Academy of Sciences of the United States of America 20210601 25

Mammalian cells equalize X-linked dosages between the male (XY) and female (XX) sexes by silencing one X chromosome in the female sex. This process, known as "X chromosome inactivation" (XCI), requires a master switch within the X inactivation center (<i>Xic</i>). The <i>Xic</i> spans several hundred kilobases in the mouse and includes a number of regulatory noncoding genes that produce functional transcripts. Over three decades, transgenic and deletional analyses have demonstrated both the nece ...[more]

PMID: 34161282

Similar Datasets

Project description:IntroductionThe bicoid (bcd) gene in Drosophila has served as a paradigm for a morphogen in textbooks for decades. Discovered in 1986 as a mutation affecting anterior development in the embryo, its expression pattern as a protein gradient later confirmed the prediction from transplantation experiments. These experiments suggested that the protein fulfills the criteria of a true morphogen, with the existence of a homeodomain crucial for activation of genes along the anterior-posterior axis, based on the concentration of the morphogen. The bcd gene undergoes alternative splicing, resulting in, among other isoforms, a small and often neglected isoform with low abundance, which lacks the homeodomain, termed small bicoid (smbcd). Most importantly, all known classical strong bcd alleles used in the past to determine bcd function apparently do not affect the function of this isoform.ResultsTo overcome the uncertainty regarding which isoform regulates what, I removed the bcd locus entirely using CRISPR technology. bcdCRISPR eggs exhibited a short and round appearance. The phenotype could be ascribed to smbcd because all bcd alleles affecting the function of the major transcript, termed large bicoid (lgbcd) showed normally sized eggs. Several patterning genes for the embryo showed expression in the oocyte, and their expression patterns were altered in bcdCRISPR oocytes. In bcdCRISPR embryos, all downstream segmentation genes showed altered expression patterns, consistent with the expression patterns in "classical" alleles; however, due to the altered egg geometry resulting in fewer blastoderm nuclei, additional constraints came into play, further affecting their expression patterns.ConclusionsThis study unveils a novel and fundamental role of bcd in shaping the egg's geometry. This discovery demands a comprehensive revision of our understanding of this important patterning gene and prompts a reevaluation of past experiments conducted under the assumption that bcd mutants were bcdnull-mutants.

Dataset Information

Revisiting the consequences of deleting the X inactivation center.

Publications

Revisiting the consequences of deleting the X inactivation center.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets