Abstract 19222: Hypoxia Regulated Circular RNAs Control Endothelial Cell Functions (Best of Basic Science Abstract)
Circular RNAs (circRNAs) are non-coding RNAs generated by back-splicing. Back-splicing has been considered as a rare event, but circRNAs were recently found to be abundantly expressed among a variety of human cells and tissues. Nevertheless, the expressional regulation, processing and biological functions of circRNAs are largely unknown. Cytoplasmic circRNAs can bind and trap microRNAs, whereas nuclear circRNAs may affect host gene expression. However, the expression, regulation and functions of circRNAs in endothelial cells have not been determined so far.
In this study, basal expression and regulation of circRNAs by hypoxia in human umbilical endothelial cells (HUVEC) were analyzed using deep sequencing. Among the identified 7,388 circRNAs, 2,875 had not been annotated before. We further validated the expression of 40 selected circRNAs by RT-PCR and found that the majority is resistant to RNase R digestion, lacks polyadenylation and is localized to the cytoplasm. Cloning and subsequent sequencing validated the newly generated back splice sites for selected circRNAs. Furthermore, analysis of RNA-seq data revealed that circRNAs, particularly the cytoplasmatic circular RNA cZNF292, are significantly regulated by hypoxia in HUVECs. The siRNA-mediated knockdown of HIF-1α had no effect on cZNF292 induction under hypoxia, suggesting a HIF-1α independent regulation. Most importantly, siRNA-mediated knockdown of cZNF292 significantly reduced spheroid sprouting and network formation of endothelial cells. Furthermore, knockdown of cZNF292 had no effect on its host gene expression. Exon array analysis after cZNF292 knockdown revealed a significant expressional upregulation of 167 as well as a significant expressional downregulation of 123 genes of which most were associated with metabolic processes according to GO annotation. Analysis of Ago-HITS-CLIP data revealed no putative miR-binding sites, suggesting that cZNF292 does not act as a miR-sponge.
Taken together, we show for the first time the expression, regulation and function of circRNAs in endothelial cells. The circRNA cZNF292 is regulated by hypoxia and has an important angiogenic function in endothelial cells.
Author Disclosures: A.W. Heumüller: None. J. Boeckel: Other; Modest; Applied for a patent. N. Jaé: Other; Modest; Applied for a patent. Y. Ponomareva: None. W. Chen: None. R.A. Boon: None. D. John: None. A.M. Zeiher: Other; Modest; Applied for a patent. S. Uchida: None. S. Dimmeler: Consultant/Advisory Board; Modest; Miragen. Research Grant; Significant; ERC, DFG.
- © 2015 by American Heart Association, Inc.