Characterization of circular RNAs in dorsal root ganglia after central and peripheral axon injuries

Genome-wide profiling and functional characterization of circular RNAs in neural development and injury: insights from a rat model research

Circular RNAs (circRNAs) have re-emerged as promising gene regulators in various physiological and pathological conditions. However, the expression patterns of circRNAs in the developing spinal cord of mammals and the comprehensive distribution of circRNAs across different tissues remain poorly understood. In this study, rats were used as the model organism. We conducted a comprehensive analysis of 15 RNA-Seq datasets comprising 217 rat samples and developed a web-based resource, CiRNat, to facilitate access to these data. We identified 15,251 credible circRNAs and validated them through experimental approaches. Notably, we observed two significant time points for circRNA increase during spinal cord development, approximately at embryonic day 14 (E14d) and postnatal week 4 (P4w). Analysis of circRNA expression in various rat tissues revealed higher expression levels in central nervous system tissues compared to peripheral nervous system tissues and other tissues. Furthermore, some highly abundant circRNAs exhibited tissue- and species-specific expression patterns and differed from their cognate linear RNAs, such as those derived from Gigyf2. Integrating polysome profiling and bioinformatic predictions suggested potential functions of certain circRNAs as miRNA sponges and translational templates. Collectively, this study provides the first comprehensive landscape of circRNAs in the developing spinal cord, offering an important resource and new insights for future exploration of functional circRNAs in central nervous system development and related diseases.

circRNA landscape in dorsal root ganglia from mice with collagen antibody-induced arthritis

Circular RNAs are a novel class of RNA molecules that are covalently closed into a ring structure. They are an epigenetic regulatory mechanism, and their best-studied function is regulation of microRNA activity. As such circular RNAs may be involved in the switch from acute to chronic pain. They have previously been studied in the context of neuropathic pain models, but their importance in inflammation-induced chronic pain models is unexplored. Microarray analysis of dorsal root ganglia collected in the late phase of collagen antibody-induced arthritis (day 59) were used to elucidate the relevance of circular RNAs in the mechanical hypersensitivity caused by this model. 120 circular RNA genes were found to be significantly differentially regulated in female BALB/c mice with collagen antibody-induced arthritis. Six genes were chosen for RT-qPCR analysis in the late (day 54-60) as well as the inflammatory (day 11-12) phase of this model. This validated an increase in circNufip1 expression in the late phase of collagen antibody-induced arthritis. Additionally, it was found that circVps13 and circMicall1 are upregulated in the inflammatory phase. Interestingly, no changes were found in dorsal root ganglia from mice injected with Freund's Complete Adjuvant (day 3) nor mice with spared nerve injury (day 20), despite their similarities to inflammatory and late phase collagen antibody-induced arthritis, respectively. This study provides evidence that mild circular RNA changes occur in dorsal root ganglia of mice with collagen antibody-induced arthritis that are, bioinformatically, predicated to be involved in processes relevant to sensitization.