Widespread induction of SINE-RNA expression in the mouse brain following transient focal ischemia.

Ischemic stroke triggers rapid transcriptional changes in the brain, including the induction of noncoding RNAs, which are well-established regulators of post-stroke pathophysiology. Among the numerous classes of noncoding RNAs, short interspersed nuclear element RNAs (SINE-RNAs) are transcribed by Pol III and reported to be upregulated in various paradigms of cellular stress. In the ischemic brain, Pol III-driven gene expression is not well-studied and the expression of SINE-RNAs is virtually unmapped. In the current study, we used a mouse model of transient focal ischemia to evaluate for the first time post-stroke SINE-RNA expression in the cerebral cortex on a genome-wide scale. We observed SINE-RNA induction as early as 0 to 3 h of reperfusion and peak expression at 6 h of reperfusion, with 335 SINE-RNAs induced at this timepoint as compared to sham controls. Many of these transcripts remained induced through later timepoints during the acute phase of reperfusion (24 h). Fluorescence in situ hybridization against the SINE-RNAs, combined with immunohistochemistry for cell-type markers, revealed that these RNAs are localized to the nuclei of post-ischemic neurons and microglia in the ipsilateral cortex and hippocampus in both males and females. Further, we found that SINE-RNA expression was recapitulated in vitro following oxygen-glucose deprivation in HT22 hippocampal neurons, showing that they are reproducibly expressed in neurons in both in vivo and in vitro models of ischemia. Together, this is the first study to map genome-wide SINE-RNA expression in the post-ischemic brain and reveals a new layer of the noncoding transcriptome that may play a role in the post-stroke pathophysiology.