Fig 1: Identification of a long noncoding RNA abundantly expressed in cardiomyocytes.a Distribution of RNAs identified in gene trapping strategy in ES cells. b Expression of lacZ from targeting vector at mouse E12.5. Heart cells show X-gal positivity. c Structure of the WT allele, as well as the trapping vector pU21 and the Caren insertion site in mouse chromosome 8. d UCSC genome browser snapshot showing locus containing 2500002B13Rik (Caren) and flanking Hmgb2 and Sap30 genes on chromosome 8 (NCBI37/mm9), and RNA-seq signals in adult mouse heart based on ENCODE/CSHL, as well as H3K4me3 and H3K36me3 ChIP-seq signals in mouse adult heart based on ENCODE/LICR. e X-gal staining in heterozygous T167 (Caren+/β-geo) mice. LacZ expression was detected in the heart (top row, left) and in the myocardium of the left ventricle (bottom row, left). Sections were counterstained with nuclear fast red. Scale bar, 100 μm. f Quantitative RT-PCR analysis of Myh6 and 2500002B13Rik (Caren) expression in GFP+ and GFP− cells isolated from heart tissues of αMHC-EGFP Tg mice (n = 6 per group). Values derived from GFP+ cells were set to 1. g Protein coding potential scores of known mRNAs (Gapdh, Actinβ, and Myh6) or lncRNAs [Xist, Braveheart (Bvht), Fendrr, and Mhrt] compared to Caren. h Quantitative RT-PCR analysis of Caren, Rps18 (a mature mRNA), and Hotair (a nuclear lncRNA) expression in nuclear and cytoplasmic fractions from the whole heart of 12-week-old wild-type mice (n = 6 per group). For Caren and Rsp18, cytoplasmic expression levels were set to 1. For Hotair, nuclear expression levels were set to 1. i Relative Caren transcript levels in hearts from 2 (2M)-month-old and 24 (24M)-month-old WT mice (2 M: n = 7, 24 M: n = 6) (left), from WT mice 2 weeks after Angiotensin II (Ang II) or vehicle treatment (n = 5 per group) (middle), and from WT mice 6 weeks after TAC or sham surgery (sham: n = 5, TAC: n = 6) (right). Levels seen in respective 2-month-old, vehicle-treated, or sham-operated mice were set to 1. Box plots for f, h, and i present min to max, median, and all points. Statistical significance was determined by a two-sided unpaired Student’s t-test (f, h, i). †p < 0.0001, n.s; not significant, between genotypes or groups.