Abstract WP314: Post-Stroke Regulation of α-Synuclein by microRNA miR-7 and Circular RNA CDR1as

Abstract

α-Synuclein (α-Syn) induced after stroke is a known mediator of ischemic brain damage. We currently evaluated the molecular mechanisms that regulate α-Syn expression in the post-ischemic brain. The miR-7 is an abundantly expressed miRNA in brain that targets α-Syn mRNA with high energy. In adult mice subjected to transient middle cerebral artery occlusion (MCAO), miR-7 levels were down-regulated in the cerebral cortex as early as 3h and late as 3 days of reperfusion which leads to derepression of α-Syn mRNA that facilitates α-Syn protein translation. Treating mice after transient MCAO with a miR-7 mimic significantly curtailed ischemic brain damage and promoted better motor function recovery. However, the pri-miR-7a and -7b levels were unaltered indicating that the post-ischemic reduction in miR-7 levels are not due to reduced expression of miR-7 gene. With bioinformatics, we observed that the circRNA CDR1as contains >70 binding sites with good affinity for miR-7. CDR1as is thought to sequester miR-7 to protect it from degradation and/or to transport it to the sites of its necessity. Transient MCAO also led to down-regulation of CDR1as expression between 3h and 3 days of reperfusion. When CDR1as levels were replenished in the post-ischemic mice with a CDR1as AAV9 vector, the miR-7 levels as well as binding of CDR1as to Ago2/miR-7 increased and α-Syn protein levels decreased significantly in the peri-infarct cortex. Furthermore, the CDR1as AAV9 treated mice showed decreased markers of inflammation and apoptosis, better motor function recovery and smaller infarcts. Our studies thus indicate that α-Syn in the post-ischemic brain is controlled by the mutual interaction of a miRNA (miR-7) and a circRNA (CDR1as). Thus, understanding noncoding RNA interactions and mechanisms might help to design better therapies to alleviate post-stroke neuronal damage.