Abstract:SUMMARYMany organisms show major chromosomal differences between sexes. In mammals, females have two copies of a large, gene-rich chromosome, the X, whereas males have one X and a small, gene-poor Y. The imbalance in expression of several hundred genes is lethal if not dealt with by dosage compensation. The male-female difference is addressed by silencing of genes on one female X early in development. However, both males and females now have only one active X chromosome. This is compensated by twofold up-regul… Show more
“…Nonetheless, antisense RNA has been implicated in the most widely studied epigenetic phenomena of all, imprinting and X inactivation (see Barlow andBartolomei 2014 andBrockdorff andTurner 2014, respectively). In the case of X inactivation, a 17-kb spliced and polyadenylated noncoding RNA known as Xist is required to silence the inactive X chromosome from which it is expressed.…”
Section: Conservation Of Rnai-mediated Chromatin Modifications In Animentioning
SUMMARYThe involvement of RNA interference (RNAi) in heterochromatin formation has become clear largely through studies in the fission yeast Schizosaccharomyces pombe and plants like Arabidopsis thaliana. This article discusses how heterochromatic small interfering RNAs are produced and how the RNAi machinery participates in the formation and function of heterochromatin.Outline
“…Nonetheless, antisense RNA has been implicated in the most widely studied epigenetic phenomena of all, imprinting and X inactivation (see Barlow andBartolomei 2014 andBrockdorff andTurner 2014, respectively). In the case of X inactivation, a 17-kb spliced and polyadenylated noncoding RNA known as Xist is required to silence the inactive X chromosome from which it is expressed.…”
Section: Conservation Of Rnai-mediated Chromatin Modifications In Animentioning
SUMMARYThe involvement of RNA interference (RNAi) in heterochromatin formation has become clear largely through studies in the fission yeast Schizosaccharomyces pombe and plants like Arabidopsis thaliana. This article discusses how heterochromatic small interfering RNAs are produced and how the RNAi machinery participates in the formation and function of heterochromatin.Outline
“…One can envisage two very general models for regulating a whole chromosome. A single site or a very limited number of sites might control the chromosome in cis, as is the case in mammalian X inactivation via the region called the X inactivation center (see Brockdorff and Turner 2014). This mechanism requires either compartmentalization of the complex to a specific place in the nucleus or regulation over very long distances through the spreading of factors from the central control region to the rest of the chromosome.…”
Section: High-resolution Analysis Of Msl Bindingmentioning
confidence: 99%
“…We now know that in organisms belonging to distantly related groups-from round worms to mammals-transcriptional regulation leading to equal products of X-linked genes in males and females has been achieved in different ways: by decreasing the level of transcription of the two doses of X-linked genes in hermaphrodites relative to males (Caenorhabditis elegans) or by hypertranscribing the X chromosome in both males and females and then shutting down one of the two X chromosomes throughout most of its length in the somatic cells of females (mammals). The mechanisms underlying dosage compensation in these forms are described in Strome et al (2014) and Brockdorff and Turner (2014).…”
Section: The Phenomenon Of Dosage Compensation Was Discovered In Drosmentioning
confidence: 99%
“…One of the most intriguing and mysterious aspects of dosage compensation in both mammals and Drosophila is the role of ncRNAs in targeting compensation to the correct chromosome (reviewed in ; also see Brockdorff and Turner 2014). Two ncRNAs, called RNA on X (roX), are dissimilar in size and sequence, and yet function redundantly to target the MSL complex to the male X chromosome in Drosophila (Meller and Rattner 2002).…”
Section: Noncoding Rox Rnas Facilitate Assembly and Targeting Of The mentioning
SUMMARYDosage compensation in Drosophila increases the transcription of genes on the single X chromosome in males to equal that of both X chromosomes in females. Site-specific histone acetylation by the malespecific lethal (MSL) complex is thought to play a fundamental role in the increased transcriptional output of the male X. Nucleation and sequence-independent spreading of the complex to active genes serves as a model for understanding the targeting and function of epigenetic chromatin-modifying complexes. Interestingly, two noncoding RNAs are key for MSL assembly and spreading to active genes along the length of the X chromosome.
“…In female mouse embryos (XX), the paternally inherited X chromosome is always inactivated during the cleavage stages and remains so in the extraembryonic tissues (i.e., the TE and the placenta; Lee 2003, Okamoto et al 2005). But, in the ICM, the inactive X is reactivated and this is followed by random inactivation of one X chromosome after differentiation in the ICM-derived lineages (Mak et al 2004; for more detail, see Figs 4 and 6 of Brockdorff and Turner 2014). Mechanistically, imprinted X inactivation (i.e., paternal X inactivation) in the preimplantation embryo involves expression of the noncoding RNA Xist from the paternal X chromosome, whose "coating" of the chromosome is thought to lead to gene silencing and the establishment of repressive epigenetic modifications (Heard 2004).…”
Section: From the Zygote To The Blastocystmentioning
SUMMARYEpigenetic mechanisms play an essential role in the germline and imprinting cycle. Germ cells show extensive epigenetic programming in preparation for the generation of the totipotent state, which in turn leads to the establishment of pluripotent cells in blastocysts. The latter are the cells from which pluripotent embryonic stem cells are derived and maintained in culture. Following blastocyst implantation, postimplantation epiblast cells develop, which give rise to all somatic cells as well as primordial germ cells, the precursors of sperm and eggs. Pluripotent stem cells in culture can be induced to undergo differentiation into somatic cells and germ cells in culture. Understanding the natural cycles of epigenetic reprogramming that occur in the germline will allow the generation of better and more versatile stem cells for both therapeutic and research purposes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.