Enrichment of Circular RNA Expression Deregulation at the Transition to Recurrent Spontaneous Seizures in Experimental Temporal Lobe Epilepsy

Abstract

Mesial temporal lobe epilepsy (mTLE) is a common form of epilepsy and is characterized by recurrent spontaneous seizures originating from the temporal lobe. The majority of mTLE patients develop pharmacoresistance to available anti-epileptic drugs (AEDs) while exhibiting severe pathological changes that can include hippocampal atrophy, neuronal death, gliosis and chronic seizures. The molecular mechanisms leading to mTLE remain incompletely understood, but are known to include defects in post-transcriptional gene expression regulation, including in non-coding RNAs (ncRNAs). Circular RNAs (circRNAs) are a class of recently rediscovered ncRNAs with high levels of expression in the brain and proposed roles in diverse neuronal processes. To explore a potential role for circRNAs in epilepsy, RNA-sequencing (RNA-seq) was performed on hippocampal tissue from a rat perforant pathway stimulation (PPS) model of TLE at different post-stimulation time points. This analysis revealed 218 differentially expressed (DE) circRNAs. Remarkably, the majority of these circRNAs were changed at the time of the occurrence of the first spontaneous seizure (DOFS). The expression pattern of two circRNAs, circ_Arhgap4 and circ_Nav3, was further validated and linked to miR-6328 and miR-10b-3p target regulation, respectively. This is the first study to examine the regulation of circRNAs during the development of epilepsy. It reveals an intriguing link between circRNA deregulation and the transition of brain networks into the state of spontaneous seizure activity. Together, our results provide a molecular framework for further understanding the role and mechanism-of-action of circRNAs in TLE.

Expression of Circ_Satb1 Is Decreased in Mesial Temporal Lobe Epilepsy and Regulates Dendritic Spine Morphology

“…Unfortunately, their specific neuronal functions remain poorly understood. Our own work and that of others shows deregulated expression of circRNAs in mTLE patients and in experimental models of epilepsy (e.g., Gong et al, 2018 ; Lee et al, 2018 ; Li et al, 2018 ; Gray et al, 2020 ; Gomes-Duarte et al, 2021 ). For example, we have recently reported enrichment of circRNA deregulation at the transition to recurrent spontaneous seizures ( Gomes-Duarte et al, 2021 ).…”

“…Library preparation and circRNA analysis using RNA-seq were performed as described previously ( Gomes-Duarte et al, 2021 ), with minor modifications (human circRNA detection). Purified RNA (2 μg input) was depleted of ribosomal RNA (rRNA) using the Ribo-Zero Magnetic Kit (human/mouse/rat; Illumina).…”

“…RNase R treatment, cDNA synthesis and PCR were performed as reported previously with minor modifications ( Gomes-Duarte et al, 2021 ). RNase R treatment was performed as follows: 5 μg of total RNA was diluted in 20 μl of water with 4U RNase R/μg (Epicenter), 2 μl of enzyme buffer and then incubated for 20 min at 37°C.…”

A Narrative Review of Circular RNAs in Brain Development and Diseases of Preterm Infants

“…Another experiment interestingly demonstrated that overexpressed circ-DROSHA weakened the neural damage of the TLE cell model (71). A recent study also confirmed the altered circRNAs expression during epileptogenesis (61). If circRNAs could impair paradoxical discharge, TLE would be suppressed.…”

Nanotechnology‐Assisted RNA Delivery: From Nucleic Acid Therapeutics to COVID‐19 Vaccines

“…The potential of RNA for the treatment of neurodegenerative diseases is under constant investigation, as demonstrated by very recent studies in this field. [ 303 ] Positive outcomes have motivated researchers to identify strategies for aiding the delivery of RNA, injected locally into the brain or at a systemic level, for the treatment of these diseases. [ 304 , 305 , 306 ] To be suitable for this specific application, a proper design of delivery systems is required to provide them in vivo stability and transcytotic potential.…”