title: Uncoupling antisense-mediated silencing and DNA methylation in the imprinted Gnas cluster.
abstract: There is increasing evidence that non-coding macroRNAs are major elements for silencing imprinted genes, but their mechanism of action is poorly understood. Within the imprinted Gnas cluster on mouse chromosome 2, Nespas is a paternally expressed macroRNA that arises from an imprinting control region and runs antisense to Nesp, a paternally repressed protein coding transcript. Here we report a knock-in mouse allele that behaves as a Nespas hypomorph. The hypomorph mediates down-regulation of Nesp in cis through chromatin modification at the Nesp promoter but in the absence of somatic DNA methylation. Notably there is reduced demethylation of H3K4me3, sufficient for down-regulation of Nesp, but insufficient for DNA methylation; in addition, there is depletion of the H3K36me3 mark permissive for DNA methylation. We propose an order of events for the regulation of a somatic imprint on the wild-type allele whereby Nespas modulates demethylation of H3K4me3 resulting in repression of Nesp followed by DNA methylation. This study demonstrates that a non-coding antisense transcript or its transcription is associated with silencing an overlapping protein-coding gene by a mechanism independent of DNA methylation. These results have broad implications for understanding the hierarchy of events in epigenetic silencing by macroRNAs.
authors: Medical Research Council Mammalian Genetics Unit, Harwell Science and Innovation Campus, Harwell, United Kingdom.
authors: Christine M
authors: CM
authors: Williamson
authors: Simon T
authors: ST
authors: Ball
authors: Claire
authors: C
authors: Dawson
authors: Stuti
authors: S
authors: Mehta
authors: Colin V
authors: CV
authors: Beechey
authors: Martin
authors: M
authors: Fray
authors: Lydia
authors: L
authors: Teboul
authors: T Neil
authors: TN
authors: Dear
authors: Gavin
authors: G
authors: Kelsey
authors: Jo
authors: J
authors: Peters
mesh_terms: D000483:Alleles; D000818:Animals; D030801:Animals, Genetically Modified; D002864:Chromogranins; D019175:DNA Methylation / Q000235:genetics*; D005260:Female; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics* / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000235:genetics; D023061:Gene Order; D020868:Gene Silencing; D018390:Gene Targeting; D018392:Genomic Imprinting / Q000235:genetics*; D006657:Histones / Q000378:metabolism; D008297:Male; D051379:Mice; D009154:Mutation / Q000235:genetics; D016372:RNA, Antisense / Q000235:genetics*
chemical_list: D002864:Chromogranins; D006657:Histones; D016372:RNA, Antisense; C498642:Gnas protein, mouse; D019205:GTP-Binding Protein alpha Subunits, Gs