Abstracts

Rationale: Epilepsy is the fourth most prevalent neurological disorder with an incidence of 1 in 26 individuals. While a number of anticonvulsants exist to treat single seizure episodes, no antiepileptogenic drugs are currently available to stop disease progression. Methods: Epileptogenesis is associated with alterations in synaptic plasticity, cell death, inflammation, and a reduction in seizure threshold. To investigate which transcriptional regulators are responsible for these outcomes, we analyzed a set of dentate granule cell expression profiles laser captured after Status Epilepticus (SE) in three rat seizure models: pilocarpine, kainic acid, and self-sustained SE. Results: Our analysis predicts that increased Enhancer of Zeste Homolog 2 (EZH2) function is a principle driver of gene expression changes during epileptogenesis across epilepsy models. This is significant because EZH2 plays an important role as part of the Polycomb Repressive Complex during development, where it epigenetically and stably silences genes. In this study, we have used the kainic acid mouse model to test this prediction and characterize the molecular function of EZH2 after SE. We have found that EZH2 protein levels are robustly induced after SE, peaking at two days with a 6.3-fold up regulation and remaining increased out to five days. We also provide evidence that this increase is functional, by observing a down regulation in EZH2 target gene expression as much as 10 days after SE. Through immunofluorescence, we demonstrate that increased EZH2 levels are localized to hippocampal neurons. Administration of the small-molecule EZH2 inhibitor UNC1999 to epileptic mice significantly increases seizure burden, suggesting a protective rather than pathological role for EZH2 upregulation. We validate the presence of UNC1999 in the brain by performing LC/MS on UNC1999 and vehicle treated hippocampal tissue. With these data, we are the first lab to show that UNC1999 crosses the blood-brain-barrier after systemic delivery. Conclusions: Our aim is to determine the mechanism by which EZH2 becomes up regulated after SE and determine if exogenous delivery of EZH2 is sufficient to decrease seizure activity after the onset of epileptogenesis. This project is one of the first to characterize a role for EZH2 in epileptogenesis and may foster the development of EZH2 agonists as potential anti-epileptogenic drugs. Deciphering the role of EZH2 will bring novel insight into epileptogenesis and shed light on novel strategies for treating one of the most common neurological disorders today. Funding: NIH Grant F99 NS105211, NIH Grant R21 NS093364, CURE Challenge Award, Lily's Fund Spark Award