Transient middle cerebral artery occlusion in mice induces neuronal expression of RNF213, a susceptibility gene for moyamoya disease

Abstract

Although recent genome-wide and locus-specific association studies revealed that the RING finger protein 213 (RNF213) gene is an important susceptibility gene for moyamoya disease (MMD), the exact mechanism by which the genetic alteration of RNF213 contributes to the development of MMD has not yet been elucidated. A quantitative reverse transcription polymerase chain reaction (PCR) analysis revealed that the constitutive expression of the RNF213 gene was very low in adult and embryonic brain tissue. However, information regarding the temporal and spatial expression patterns of the RNF213 gene under the condition of cerebral ischemia, which is one of characteristic pathologies associated with MMD, is currently limited. In order to address this critical issue, Rnf213 mRNA expression was investigated in mouse brains subjected to 60 min of transient middle cerebral artery occlusion (tMCAO). Male C57BL6/j mice underwent tMCAO through the intraluminal blockade of MCA. Expression of the Rnf213 gene in the tMCAO brain was investigated with in situ RNA hybridization and a real-time PCR analysis from 1 to 72 h after tMCAO. In situ RNA hybridization revealed a significant increase in Rnf213 mRNA levels in the cerebral cortex supplied by the affected MCA, especially at the penumbra area, as early as 6h after tMCAO, and these levels had increased further by 24 h. Rnf213 gene expression remained unchanged in the non-ischemic hemisphere or control specimens. Double staining of Rnf213 mRNA with NeuN immunohistochemistry revealed Rnf213 hybridization signal expression mostly in neurons. The real-time PCR analysis confirmed induction of the Rnf213 gene after tMCAO. Therefore, the Rnf213 gene was up-regulated in the ischemic brain, especially at the penumbra area, 6 h after tMCAO. Early increases in RNF213 gene expression in neurons after tMCAO indicate its involvement in cerebral ischemia, which is an underlying pathology of MMD. Further investigation is required to clarify its exact role in the pathophysiology of MMD.

Keywords: In situ RNA hybridization; Moyamoya disease; RNF213 gene; Transient focal cerebral ischemia (tFCI).