Transient Global Cerebral Ischemia Induces RNF213, a Moyamoya Disease Susceptibility Gene, in Vulnerable Neurons of the Rat Hippocampus CA1 Subregion and Ischemic Cortex

The RING finger protein 213 (RNF213) is an important susceptibility gene for moyamoya disease (MMD) and is also implicated in other types of intracranial major artery stenosis/occlusion (ICAS); however, the role of RNF213 in the development of ICAS including MMD is unclear. The constitutive expression of the RNF213 gene is relatively weak in brain tissue, while information regarding the expression patterns of the RNF213 gene under cerebral ischemia, which is one of characteristic pathologies associated with ICAS, is currently limited. Our objective was to address this critical issue, and we investigated Rnf213 mRNA expression in rat brains after 5 minutes of transient global cerebral ischemia (tGCI) by occluding the common carotid arteries coupled with severe hypotension. Rnf213 gene expression patterns were investigated with in situ RNA hybridization and a real-time polymerase chain reaction (PCR) from 1 to 72 hours after tGCI. In situ RNA hybridization revealed a significant increase in Rnf213 mRNA levels in the hippocampus CA1 sub-region 48 hours after tGCI. The significant induction of the Rnf213 gene was also evident in the ischemic cortex. Double staining of Rnf213 mRNA with NeuN immunohistochemistry revealed Rnf213 hybridization signal expression exclusively in neurons. The real-time PCR analysis confirmed the induction of the Rnf213 gene after tGCI. The up-regulation of the Rnf213 gene in vulnerable neurons in the hippocampus CA1 after tGCI suggests its involvement in forebrain ischemia, which is an underlying pathology of MMD. Further investigations are needed to elucidate its exact role in the pathophysiology of ICAS including MMD.