Covalently closed single-stranded circular RNAs (circRNAs) consist of introns or exons and are widely present in eukaryotic cells. CircRNAs generally have low expression levels and relatively stable structures compared with messenger RNAs (mRNAs), most of which are located in the cytoplasm and often act in cell type and tissue-specific manners, indicating that they may serve as novel biomarkers. In recent years, circRNAs have gradually become a hotspot in the field of RNA and cancer research, but the functions of most circRNAs have not yet been discovered. Known circRNAs can affect the biogenesis of cancers in diverse ways, such as functioning as a microRNA (miRNA) sponges, combining with RNA binding proteins (RBPs), working as a transcription factor and translation of proteins. In this review, we summarize the characteristics and types of circRNAs, introduce the biogenesis of circRNAs, discuss the emerging functions and databases on circRNAs and present the current challenges of circRNAs studies.

Owing to the promising therapeutic effect and one-time treatment advantage, gene therapy may completely change the management of eye diseases, especially retinal diseases. Adeno-associated virus (AAV) is considered one of the most promising viral gene delivery tools because it can infect various types of tissues and is considered as a relatively safe gene delivery vector. The eye is one of the most popular organs for gene therapy, since its limited volume is suitable for small doses of AAV stably transduction. Recently, an increasing number of clinical trials of AAV-mediated gene therapy are underway. This review summarizes the biological functions of AAV and its application in the treatment of various ocular diseases, as well as the characteristics of different AAV delivery routes in clinical applications. Here, the latest research progresses in AAV-mediated gene editing and silencing strategies to modify that the genetic ocular diseases are systematically outlined, especially by base editing and prime editing. We discuss the progress of AAV in ocular optogenetic therapy. We also summarize the application of AAV-mediated gene therapy in animal models and the difficulties in its clinical transformation.

Hepatic cytokine BMP9 attenuates fatty liver by regulating the key lipid metabolism factor PPARα.

The next-generation gene editing tool, prime editing (PE), is adept at correcting point mutations precisely with high editing efficiency and rare off-target events and shows promising therapeutic value in treating hereditary diseases. Retinitis pigmentosa (RP) is the most common type of inherited retinal dystrophy and is characterized by progressive degeneration of retinal photoreceptors and, consequently, visual decline. To date, effective treatments for RP are lacking. Herein, a PE system is designed to target the PDE6B Y347X mutation in the rd1 mouse strain, a preclinical RP model. We screen and develop the PE system with epegRNA and RT^ΔRnH, which is delivered via dual-AAV in vivo with an editing efficiency of 26.47 ± 13.35%, with negligible off-target effects confirmed by AID-Seq and PE-tag. Treatment with the PE system in vivo greatly restores PDE6B protein expression and protects rod cells from degeneration. Mouse behavioural experiments also show that compared with no treatment, prime editing inhibits vision deterioration in littermate rd1 mice. This study provides a therapeutic opportunity for the use of PE to correct mutated RPs at the genomic level.

Gene editing ushers in a new era of disease treatment since many genetic diseases are caused by base-pair mutations in genomic DNA. With the rapid development of genome editing technology, novel editing tools such as base editing and prime editing (PE) have attracted public attention, heralding a great leap forward in this field. PE, in particular, is characterized by no need for double-strand breaks (DSBs) or homology sequence templates with variable application scenarios, including point mutations as well as insertions or deletions. With higher editing efficiency and fewer byproducts than traditional editing tools, PE holds great promise as a therapeutic strategy for human diseases. Subsequently, a growing demand for the standard construction of PE system has spawned numerous easy-to-access internet resources and tools for personalized prime editing guide RNA (pegRNA) design and off-target site prediction. In this review, we mainly introduce the innovation and evolutionary strategy of PE systems and the auxiliary tools for PE design and analysis. Additionally, its application and future potential in the clinical field have been summarized and envisaged.