Research Techniques Made Simple: Studying Circular RNA in Skin Diseases

Non-coding RNAs as skin disease biomarkers, molecular signatures, and therapeutic targets

Non-coding RNAs (ncRNAs) are emerging as biomarkers, molecular signatures, and therapeutic tools and targets for diseases. In this review, we focus specifically on skin diseases to highlight how two classes of ncRNAs-microRNAs and long noncoding RNAs-are being used to diagnose medical conditions of unclear etiology, improve our ability to guide treatment response, and predict disease prognosis. Furthermore, we explore how ncRNAs are being used as both as drug targets and associated therapies have unique benefits, risks, and challenges to development, but offer a distinctive promise for improving patient care and outcomes.

Exploring the Multifaceted Biologically Relevant Roles of circRNAs: From Regulation, Translation to Biomarkers

CircRNAs are a category of regulatory RNAs that have garnered significant attention in the field of regulatory RNA research due to their structural stability and tissue-specific expression. Their circular configuration, formed via back-splicing, results in a covalently closed structure that exhibits greater resistance to exonucleases compared to linear RNAs. The distinctive regulation of circRNAs is closely associated with several physiological processes, as well as the advancement of pathophysiological processes in several human diseases. Despite a good understanding of the biogenesis of circular RNA, details of their biological roles are still being explored. With the steady rise in the number of investigations being carried out regarding the involvement of circRNAs in various regulatory pathways, understanding the biological and clinical relevance of circRNA-mediated regulation has become challenging. Given the vast landscape of circRNA research in the development of the heart and vasculature, we evaluated cardiovascular system research as a model to critically review the state-of-the-art understanding of the biologically relevant functions of circRNAs. We conclude the review with a discussion of the limitations of current functional studies and provide potential solutions by which these limitations can be addressed to identify and validate the meaningful and impactful functions of circRNAs in different physiological processes and diseases.

A novel UVA-associated circUBE2I mediates ferroptosis in HaCaT cells

Alternative splicing of precursor messenger RNA (pre-mRNA), including linear splicing and back splicing, produces multiple isoforms that lead to diverse cell fates in response to stimuli including ultraviolet radiation (UVR). Although UVR-induced linear gene splicing has been extensively studied in skin cells, the UVR-induced gene back-splicing events that lead to the production of circular RNAs (circRNAs) have not been thoroughly investigated. The present study used circRNA transcriptome sequencing to screen the differentially expressed circRNAs in human keratinocytes (HaCaT) after UVA irradiation. A total of 312 differentially expressed circRNAs were found in HaCaT cells post-UVR. Among the UVA-induced differentially expressed circRNAs, circUBE2I-a novel circRNA formed by exons 2-6 of the UBE2I gene-was the most significantly upregulated circRNA. RT-qPCR assay further confirmed the increase of circUBE2I level in HaCaT cells after UVA irradiation or H2 O2 treatment. RNase R digestion experiment revealed the stability of circUBE2I. Overexpression of circUBE2I in keratinocytes induced ferroptosis after UVA or H2 O2 , preventable by the ferroptosis inhibitor ferrostatin-1. Our study provides new insights into the role of circular RNAs in UVA-induced skin cell damage and suggests that circUBE2I could be a therapeutic target in UVR-aroused ferroptosis in skin cells.

Presenilin-1-Derived Circular RNAs: Neglected Epigenetic Regulators with Various Functions in Alzheimer's Disease

The presenilin-1 (PSEN1) gene is crucial in developing Alzheimer's disease (AD), a progressive neurodegenerative disorder and the most common cause of dementia. Circular RNAs (circRNAs) are non-coding RNA generated through back-splicing, resulting in a covalently closed circular molecule. This study aimed to investigate PSEN1-gene-derived circular RNAs (circPSEN1s) and their potential functions in AD. Our in silico analysis indicated that circPSEN1s (hsa_circ_0008521 and chr14:73614502-73614802) act as sponge molecules for eight specific microRNAs. Surprisingly, two of these miRNAs (has-mir-4668-5p and has-mir-5584-5p) exclusively interact with circPSEN1s rather than mRNA-PSEN1. Furthermore, the analysis of pathways revealed that these two miRNAs predominantly target mRNAs associated with the PI3K-Akt signaling pathway. With sponging these microRNAs, circPSEN1s were found to protect mRNAs commonly targeted by these miRNAs, including QSER1, BACE2, RNF157, PTMA, and GJD3. Furthermore, the miRNAs sequestered by circPSEN1s have a notable preference for targeting the TGF-β and Hippo signaling pathways. We also demonstrated that circPSEN1s potentially interact with FOXA1, ESR1, HNF1B, BRD4, GATA4, EP300, CBX3, PRDM9, and PPARG proteins. These proteins have a prominent preference for targeting the TGF-β and Notch signaling pathways, where EP300 and FOXA1 have the highest number of protein interactions. Molecular docking analysis also confirms the interaction of these hub proteins and Aβ42 with circPSEN1s. Interestingly, circPSEN1s-targeted molecules (miRNAs and proteins) impacted TGF-β, which served as a shared signaling pathway. Finally, the analysis of microarray data unveiled distinct expression patterns of genes influenced by circPSEN1s (WTIP, TGIF, SMAD4, PPP1CB, and BMPR1A) in the brains of AD patients. In summary, our findings suggested that the interaction of circPSEN1s with microRNAs and proteins could affect the fate of specific mRNAs, interrupt the function of unique proteins, and influence cell signaling pathways, generally TGF-β. Further research is necessary to validate these findings and gain a deeper understanding of the precise mechanisms and significance of circPSEN1s in the context of AD.

Exosomal circular RNAs: A chief culprit in cancer chemotherapy resistance

Chemotherapy is one of the primary treatments for malignant tumors. However, the acquired drug resistance hinders clinical efficacy and leads to treatment failure in most patients. Exosomes are cell-derived vesicles with a diameter of 30-150 nm carrying and delivering substances such as DNAs, RNAs, lipids, and proteins for cellular communication in tumor development. Circular RNAs (circRNAs) present covalently closed-loop RNA structures, which regulate tumor cell proliferation, apoptosis, and metastasis by controlling different genes and signaling pathways. CircRNAs are abundant and stably expressed in exosomes. Recent studies have shown that they play critical roles in chemotherapy resistance in various cancers. In this review, we summarized the origin of exosomes and discussed the regulation mechanism of exosomal circRNAs in cancer drug resistance.