Circular RNAs in physiology and non-immunological diseases.

Circular RNAs (circRNAs) are covalently closed single-stranded RNAs. Four subclasses of circRNAs have been identified in animal cells, and they have unique features in their biogenesis, degradation, and transport. CircRNAs have diverse molecular functions in sponging miRNAs, regulating transcription, modulating RNA-binding proteins, and even encoding proteins. Some circRNAs are important regulators of various physiological processes to maintain homeostasis. Dysregulation of circRNAs is associated with human disorders, and individual circRNAs are crucial factors that contribute to major diseases including non-immunological diseases such as cancers, neurological disorders, cardiovascular disease, and metabolic disease. Debates on circRNAs have also been raised in recent years, and further studies would help to resolve these disputes and potentially lead to biomedical applications of circRNAs. All circRNAs are covalently closed single-stranded RNAs, but they are diverse in their sequence composition, metabolism, roles, and functional mechanisms. The dynamic expression and functional roles of circRNAs are closely associated with different physiological states, and various circRNAs are known to serve as crucial regulators of normal homeostasis. Perturbations in circRNA expression are linked to an array of complex diseases. In particular, numerous individual circRNAs repress or induce the initiation and/or progression of various non-immunological diseases. CircRNAs hold great potential as clinical diagnostic and prognostic markers, therapeutic targets, and even treatment reagents. [ABSTRACT FROM AUTHOR]