AUTHOR=Reynolds James P. , Miller-Delaney Suzanne F. C. , Jimenez-Mateos Eva M. , Sano Takanori , McKiernan Ross C. , Simon Roger P. , Henshall David C. 

TITLE=Transcriptional Response of Polycomb Group Genes to Status Epilepticus in Mice is Modified by Prior Exposure to Epileptic Preconditioning

JOURNAL=Frontiers in Neurology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2015.00046

DOI=10.3389/fneur.2015.00046

ISSN=1664-2295

ABSTRACT=<p>Exposure of the brain to brief, non-harmful seizures can activate protective mechanisms that temporarily generate a damage-refractory state. This process, termed epileptic tolerance, is associated with large-scale down-regulation of gene expression. Polycomb group (PcG) proteins are master controllers of gene silencing during development that are re-activated by injury to the brain. Here, we explored the transcriptional response of genes associated with polycomb repressive complex (PRC) 1 (<italic>Ring1A</italic>, <italic>Ring1B</italic>, and <italic>Bmi1</italic>) and PRC2 (<italic>Ezh1</italic>, <italic>Ezh2</italic>, and <italic>Suz12</italic>), as well as additional transcriptional regulators <italic>Sirt1</italic>, <italic>Yy1</italic>, and <italic>Yy2</italic>, in a mouse model of status epilepticus (SE). Findings were contrasted to changes after SE in mice previously given brief seizures to evoke tolerance. Real-time quantitative PCR showed SE prompted an early (1 h) increase in expression of several genes in PRC1 and PRC2 in the hippocampus, followed by down-regulation of many of the same genes at later times points (4, 8, and 24 h). Spatio-temporal differences were found among PRC2 genes in epileptic tolerance, including increased expression of <italic>Ezh2</italic>, <italic>Suz12</italic>, and <italic>Yy2</italic> relative to the normal injury response to SE. In contrast, PRC1 complex genes including <italic>Ring 1B</italic> and <italic>Bmi1</italic> displayed differential down-regulation in epileptic tolerance. The present study characterizes PcG gene expression following SE and shows prior seizure exposure produces select changes to PRC1 and PRC2 composition that may influence differential gene expression in epileptic tolerance.</p>