Project description:To test if the imprinted long non-coding RNA (lncRNA) Airn transcription or its product silences the protein-coding Igf2r gene, we shortened the endogenous lncRNA to four different lengths by inserting polyadenylation (polyA) cassettes on the paternal chromosome via homologous recombination in ES cells. ES cell differentiation was used to recapitulate the developmental onset of Airn and Igf2r imprinted expression and polyA cassettes inserted before (T3, T16, T27) or after (T31, T51) the Igf2r promoter successfully truncated Airn, with the exception of T27. RNA hybridization to a tiling array (MIRTA) demonstrated loss of Airn upstream of the Igf2r promoter (except T27) and absence of novel spliced variants in all truncation alleles. To further test the transcriptional overlap model we moved the Airn promoter ~700bp before the Igf2r TSS in ES cells that lack an endogenous paternal Airn promoter and called this cell line FAP (Forward-Airn-Promoter). RNA hybridization to a tiling array (MIRTA) demonstrated that the moved Airn promoter expresses Airn in wildtype orientation and terminates at the wildtype 3' end. ES cell lines expressing different Airn variants were differentiated on gelatinized dishes after feeder cell depletion and LIF withdrawal by 0.27M-BM-5M retinoic acid for 5 days and Airn length was assayed.
Project description:To test if the imprinted long non-coding RNA (lncRNA) Airn transcription or its product silences the protein-coding Igf2r gene, we shortened the endogenous lncRNA to four different lengths by inserting polyadenylation (polyA) cassettes on the paternal chromosome via homologous recombination in ES cells. ES cell differentiation was used to recapitulate the developmental onset of Airn and Igf2r imprinted expression and polyA cassettes inserted before (T3, T16, T27) or after (T31, T51) the Igf2r promoter successfully truncated Airn, with the exception of T27. RNA hybridization to a tiling array (MIRTA) demonstrated loss of Airn upstream of the Igf2r promoter (except T27) and absence of novel spliced variants in all truncation alleles. To further test the transcriptional overlap model we moved the Airn promoter ~700bp before the Igf2r TSS in ES cells that lack an endogenous paternal Airn promoter and called this cell line FAP (Forward-Airn-Promoter). RNA hybridization to a tiling array (MIRTA) demonstrated that the moved Airn promoter expresses Airn in wildtype orientation and terminates at the wildtype 3' end.
Project description:Long non-coding (lnc) RNAs are numerous and found throughout the mammalian genome, and many are thought to be involved in the regulation of gene expression. However, the majority remain relatively uncharacterised and of uncertain function making the use to model systems to uncover their mode of action valuable. Imprinted lncRNAs target and recruit epigenetic silencing to a cluster of imprinted genes on the same chromosome, making them one of the best characterized lncRNAs to silence distant genes in cis. In this study we examined silencing of the distant imprinted gene Slc22a3 by the lncRNA Airn in the Igf2r imprinted cluster in mouse. Previously we proposed that imprinted lncRNAs may silence distant imprinted genes by disrupting promoter-enhancer interactions by being transcribed through the enhancer, which we called the enhancer interference hypothesis. Here we tested this hypothesis by first using allele-specific chromosome conformation capture (3C) to detect interactions between the Slc22a3 promoter and the locus of the Airn lncRNA that silences it on the paternal chromosome. In agreement with the model we found interactions enriched on the maternal allele, but across the entire Airn gene consistent with multiple enhancer-promoter interactions. Therefore, to further test the enhancer interference hypothesis we devised an approach to delete the entire Airn gene. However, the deletion showed that there are no essential enhancers for Slc22a3 within the Airn gene, strongly indicating that the Airn RNA rather than its transcription is responsible for silencing distant imprinted genes. Therefore we propose an alternative hypothesis whereby the chromosome interactions may initially guide the lncRNA to target imprinted promoters and recruit repressive chromatin, and that these interactions are lost once silencing is established.
Project description:Long noncoding RNAs (lncRNAs) cause Polycomb Repressive Complexes (PRCs) to spread over broad regions of the mammalian genome. We report that in mouse trophoblast stem cells, the Kcnq1ot1 and Airn lncRNAs induce PRC-dependent chromatin modifications over multi-megabase domains. Throughout the Airn-targeted domain, extent of PRC-dependent modification correlated with intra-nuclear distance to the Airn locus, pre-existing genome architecture, and the abundance of Airn itself. Specific CpG islands displayed characteristics indicating that they nucleate the spread of PRCs upon exposure to Airn. Chromatin environments surrounding Xist, Airn, and Kcnq1ot1 suggest common mechanisms of PRC engagement and spreading. Our data indicate that lncRNA potency can be tightly linked to lncRNA abundance, and that within lncRNA-targeted domains, PRCs are recruited to CpG islands via lncRNA-independent mechanisms. We propose that CpG islands that autonomously recruit PRCs interact with lncRNAs and their associated proteins through 3-dimensional space to nucleate the spread of PRCs in lncRNA-targeted domains.
Project description:Long noncoding RNAs (lncRNAs) cause Polycomb Repressive Complexes (PRCs) to spread over broad regions of the mammalian genome. We report that in mouse trophoblast stem cells, the Kcnq1ot1 and Airn lncRNAs induce PRC-dependent chromatin modifications over multi-megabase domains. Throughout the Airn-targeted domain, extent of PRC-dependent modification correlated with intra-nuclear distance to the Airn locus, pre-existing genome architecture, and the abundance of Airn itself. Specific CpG islands displayed characteristics indicating that they nucleate the spread of PRCs upon exposure to Airn. Chromatin environments surrounding Xist, Airn, and Kcnq1ot1 suggest common mechanisms of PRC engagement and spreading. Our data indicate that lncRNA potency can be tightly linked to lncRNA abundance, and that within lncRNA-targeted domains, PRCs are recruited to CpG islands via lncRNA-independent mechanisms. We propose that CpG islands that autonomously recruit PRCs interact with lncRNAs and their associated proteins through 3-dimensional space to nucleate the spread of PRCs in lncRNA-targeted domains.
Project description:Long noncoding RNAs (lncRNAs) cause Polycomb Repressive Complexes (PRCs) to spread over broad regions of the mammalian genome. We report that in mouse trophoblast stem cells, the Kcnq1ot1 and Airn lncRNAs induce PRC-dependent chromatin modifications over multi-megabase domains. Throughout the Airn-targeted domain, extent of PRC-dependent modification correlated with intra-nuclear distance to the Airn locus, pre-existing genome architecture, and the abundance of Airn itself. Specific CpG islands displayed characteristics indicating that they nucleate the spread of PRCs upon exposure to Airn. Chromatin environments surrounding Xist, Airn, and Kcnq1ot1 suggest common mechanisms of PRC engagement and spreading. Our data indicate that lncRNA potency can be tightly linked to lncRNA abundance, and that within lncRNA-targeted domains, PRCs are recruited to CpG islands via lncRNA-independent mechanisms. We propose that CpG islands that autonomously recruit PRCs interact with lncRNAs and their associated proteins through 3-dimensional space to nucleate the spread of PRCs in lncRNA-targeted domains.
Project description:In the developing mouse embryo, expression of the lncRNA Airn induces gene silencing and recruits Polycomb Repressive Complexes (PRCs) to varying extents over a 15 megabase domain, but the mechanisms remain unclear. Using high-resolution approaches, we show in mouse trophoblast stem cells that Airn expression induces long-range changes to chromatin architecture centered around a network of CpG islands occupied by PRCs and SMC1A/Cohesin. Extent of contact with Airn predicts underlying intensity of Polycomb-directed chromatin modifications and Airn-induced changes to chromatin architecture. Deletion of individual CpG islands alternately increase or decrease gene silencing and PRC activity over the domain in a manner predicted by changes in chromatin architecture. We conclude that Airn is a potent repressive lncRNA whose effects are controlled by an equilibratory network of DNA regulatory elements that modulate its frequency of contact with target chromatin.
Project description:In the developing mouse embryo, expression of the lncRNA Airn induces gene silencing and recruits Polycomb Repressive Complexes (PRCs) to varying extents over a 15 megabase domain, but the mechanisms remain unclear. Using high-resolution approaches, we show in mouse trophoblast stem cells that Airn expression induces long-range changes to chromatin architecture centered around a network of CpG islands occupied by PRCs and SMC1A/Cohesin. Extent of contact with Airn predicts underlying intensity of Polycomb-directed chromatin modifications and Airn-induced changes to chromatin architecture. Deletion of individual CpG islands alternately increase or decrease gene silencing and PRC activity over the domain in a manner predicted by changes in chromatin architecture. We conclude that Airn is a potent repressive lncRNA whose effects are controlled by an equilibratory network of DNA regulatory elements that modulate its frequency of contact with target chromatin.
Project description:In the developing mouse embryo, expression of the lncRNA Airn induces gene silencing and recruits Polycomb Repressive Complexes (PRCs) to varying extents over a 15 megabase domain, but the mechanisms remain unclear. Using high-resolution approaches, we show in mouse trophoblast stem cells that Airn expression induces long-range changes to chromatin architecture centered around a network of CpG islands occupied by PRCs and SMC1A/Cohesin. Extent of contact with Airn predicts underlying intensity of Polycomb-directed chromatin modifications and Airn-induced changes to chromatin architecture. Deletion of individual CpG islands alternately increase or decrease gene silencing and PRC activity over the domain in a manner predicted by changes in chromatin architecture. We conclude that Airn is a potent repressive lncRNA whose effects are controlled by an equilibratory network of DNA regulatory elements that modulate its frequency of contact with target chromatin.
Project description:Imprinted macro ncRNAs such as Airn play an important role in silencing protein-coding genes in cis, macro ncRNAs could be a common feature in all imprinted gene clusters. By applying the RNA Expression on Tiling Array (RETA) technique, macro ncRNAs were found to be abundant in 26 known mouse genomic regions containing imprinted genes were detected. All well-known imprinted macro ncRNAs were up-regulated upon depletion of DNA methylation.