Identification of lncRNAs expressed in fetal liver and erythroid cells. (A) Workflow for lncRNA discovery. See text and supplemental “Methods” for details. (B) Overlap between lncRNAs annotated in Ensembl, UCSC, or RefSeq databases and lncRNAs identified in this study. (C) Definitions of different classes of lncRNAs based on their genomic region of origin. (D) Distribution of 655 lncRNAs expressed in fetal liver into different lncRNA classes.