The Airn lncRNA does not require any DNA elements within its locus to silence distant imprinted genes

PLoS Genet. 2019 Jul 22;15(7):e1008268. doi: 10.1371/journal.pgen.1008268. eCollection 2019 Jul.


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 of model systems to uncover their mode of action valuable. Imprinted lncRNAs target and recruit epigenetic silencing factors to a cluster of imprinted genes on the same chromosome, making them one of the best characterized lncRNAs for silencing 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 across the entire Airn gene consistent with multiple enhancer-promoter interactions. Therefore, to 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 Slc22a2, Pde10a and Slc22a3 within the Airn gene, strongly indicating that the Airn RNA rather than its transcription is responsible for silencing distant imprinted genes. Furthermore, we found that silent imprinted genes were covered with large blocks of H3K27me3 on the repressed paternal allele. 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Enhancer Elements, Genetic*
  • Female
  • Gene Silencing*
  • Genomic Imprinting
  • Histones / metabolism
  • Male
  • Mice
  • Organic Cation Transport Proteins / genetics*
  • Organic Cation Transporter 2 / genetics
  • Phosphoric Diester Hydrolases / genetics
  • Promoter Regions, Genetic
  • RNA, Long Noncoding / genetics*
  • Receptor, IGF Type 2 / genetics
  • Sequence Deletion


  • Air non-coding RNA, mouse
  • Histones
  • Organic Cation Transport Proteins
  • Organic Cation Transporter 2
  • RNA, Long Noncoding
  • Receptor, IGF Type 2
  • Slc22a2 protein, mouse
  • solute carrier family 22 (organic cation transporter), member 3
  • Pde10a protein, mouse
  • Phosphoric Diester Hydrolases

Grant support

This work was partly supported by a grant awarded to Quanah J Hudson (Grant no: P25185-B22) by the Austrian Science Fund (FWF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.