Abstract 10192: Circular RNA Formation in the Failing Heart is Enhanced by the Reduction of Adenosine-to-Inosine RNA Editing

• Published in: Circulation (New York, N.Y.) N.Y.), 2021-11, Vol.144 (Suppl_1), p.A10192-A10192
• Main Authors: Kokot, Karoline Elizabeth, Kneuer, Jasmin M, John, David, Moebius-Winkler, Maximilian N, Müller, Marion, Andritschke, Michael, Gaul, Susanne, Sheikh, Bilal N, Haas, Jan, Thiele, Holger, Leuschner, Florian, Dimmeler, Stefanie, Meder, Benjamin, Laufs, Ulrich, Boeckel, Jes-Niels
• Format: Article
• Language: English
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/circ.144.suppl_1.10192

IntroductionAdenosine-to-Inosine (A-to-I) RNA editing is a post-transcriptional modification process regulating RNA stability and alternative splicing. A-to-I RNA editing is conducted by the enzymes ADAR1 and ADAR2 and mainly targets Alu elements, primate-specific elements which have been associated with the formation of circular RNA (circRNA). Although differential expression of circRNAs has been studied in heart failure (HF), the extent of A-to-I RNA editing and consequences in the human heart remain largely unknown. Methods and ResultsWe analyzed RNA editing in human heart samples of HF (n=20) patients and controls (n=10) using RNA sequencing. We found a reduction of A-to-I RNA editing in intronic Alu elements of protein-coding genes in HF patients compared to controls. The majority (96%) of regulated circRNAs were upregulated. The predicted back-splice sites (BSS) of 20 circRNAs were validated by qPCR. The circRNA candidates correlated with RNA editing (R=0.47, P=0.02). Among the upregulated circRNAs, we identified two circular transcripts (circAKAP13) derived from the AKAP13 gene, which showed reduced A-to-I RNA editing in HF (-70.7%, n=20). In HF, ADAR2 was reduced (-68.2%) and ADAR1 was increased (7.41±0.13 -fold) on protein level (n=3-6). The knockdown of ADAR1 did not alter circRNA levels, whereas the knockdown of ADAR2 led to significantly upregulated levels of circAKAP13 (1.88±0.42 -fold, n=6). Consistently, ADAR2 overexpression reduced circAKAP13 expression (-41%, n=3). Using two mini-genes containing exons 15-19 of the AKAP13 gene and flanking Alu elements, we found convergent Alu elements enhancing circAKAP13 expression. ConclusionIn conclusion, these data describe the A-to-I RNA editome in the human heart for the first time. Reduced A-to-I RNA editing in HF patients is associated with elevated circRNA levels. We propose a primate-specific splicing mechanism mediated by A-to-I RNA editing in the human heart. These findings contribute to a better mechanistic understanding of A-to-I RNA editing in cardiac diseases.