Identification and Characterization of Circular Intronic RNAs Derived from Insulin Gene

Circular RNAs (circRNAs) are a large family of noncoding RNAs that have emerged as novel regulators of gene expression. However, little is known about the function of circRNAs in pancreatic beta-cells. Here, transcriptomic analysis of mice pancreatic islet RNA-sequencing data identified 77 differentially expressed circRNAs between mice fed with a normal diet and a high-fat diet. Surprisingly, multiple circRNAs were derived from the intron 2 of the preproinsulin 2 (Ins2) gene and are termed as circular intronic (ci)-Ins2. The expression ofci-Ins2transcripts in mouse pancreatic islets, and beta TC6 cells were confirmed by reverse transcription PCR, DNA sequencing, and RNase R treatment experiments. The level ofci-Ins2was altered in beta TC6 cells upon exposure to elevated levels of palmitate and glucose. Computational analysis predicted the interaction of several RNA-binding proteins withci-Ins2and their flanking region, suggesting their role in theci-Ins2function or biogenesis. Additionally, bioinformatics analysis predicted the association of several microRNAs withci-Ins2. Gene ontology and pathway analysis of genes targeted by miRNAs associated withci-Ins2suggested the regulation of several key biological processes. Together, our findings indicate that differential expression of circRNAs, especiallyci-Ins2transcripts, may regulate beta-cell function and may play a critical role in the development of diabetes.