Dear Editor,
In mammalian genomes, pervasive transcription produces thousands of long noncoding RNA (lncRNA) transcripts (Djebali et al., 2012; Hon et al., 2017). Compared to protein-coding mRNAs, lncRNAs are less conserved, and often exhibit low-level, developmental stage- and tissue-specific expression (Pauli et al., 2011; Hu et al., 2012; Lee, 2012; Ulitsky and Bartel, 2013; Cech and Steitz, 2014; Hon et al., 2017). Many lncRNAs are strongly correlated with their neighboring mRNA genes in terms of expression and function, and tend to regulate nearby transcription (Orom et al., 2010; Engreitz et al., 2016;...