Projects

The primary goal of my research laboratory is to understand biological mechanisms in the brain underlying epilepsy, with the ultimate purpose of developing new therapies for epilepsy patients. We have focused on investigating cellular and molecular mechanisms of epileptogenesis and seizure-induced brain injury in animal models of epilepsy. Both pharmacological and genetic models of epilepsy are studied on the behavioral, circuit, cellular, and molecular level. A wide variety of experimental approaches are utilized, including electrophysiological (from patch-clamping in culture cells and slice preparations to in vivo video-EEG monitoring), histological (conventional and fluorescent assays), molecular biological (Western blotting, polymerase chain reaction), and modern cellular imaging (confocal and two-photon microscopy of in vivo, live slice, and fixed tissue preparations) techniques.

Mechanisms of epileptogenesis in Tuberous Sclerosis Complex and other genetic epilepsies

Epileptogenesis refers to abnormal biological processes in the brain that cause the development of epilepsy. As many patients with epilepsy are intractable to current treatments, understanding the cellular and molecular mechanisms of epileptogenesis may lead to novel, more effective therapies for epilepsy. To investigate mechanisms of epileptogenesis, in several genetic models of epilepsy, we are investigating the molecular mechanisms involved in epileptogenesis due to specific genetic mutations.

A major focus of the lab has been on an animal model of the human disease, tuberous sclerosis complex (TSC), which is one of the most common genetic causes of epilepsy. We have characterized the epilepsy in this mouse model and described a number of cellular and molecular abnormalities in glia and neurons that contribute to epileptogenesis in the mice, such as astrocyte proliferation, neuronal death, impaired glial buffering of glutamate and potassium, and dysregulation of specific cell signaling pathways. Notably, we showed that pharmacological inhibition of one of these signaling pathways (the mTOR pathway) completely prevented the development of epilepsy and the underlying brain abnormalities in these mice, which provided pre-clinical evidence supporting clinical trials and ultimately FDA approval of a mTOR inhibitor. We have investigated a number of downstream mechanisms from mTOR that contribute to epileptogenesis. Recently, we’ve focused on vascular abnormalities and blood-brain barrier breakdown in the pathophysiology of epilepsy in TSC mouse models. We’ve also utilized advanced EEG techniques in neonatal mice to investigate epileptogenesis at very early stages of brain development. Ongoing studies continue to define other mechanisms of epileptogenesis and identify novel therapeutic targets in mouse models of TSC and epilepsy.

As a common comorbidity of epilepsy, our lab has also investigated sleep disorders in TSC mouse models. We have found evidence of sleep dysfunction that related to dysregulation of hypothalamic orexin. Currently, we are further investigating the relationship between sleep and seizures in TSC mouse models.

Primarily through collaboration with other labs and as a EEG/neurophysiology core, we have also investigated epileptogenesis in a number of other mouse models of genetic epilepsies, such as neuronal ceroid lipofuscinosis and related to a variety of other genetic mutations/KO mice.

Mechanisms of epileptogenesis in acquired epilepsies due to brain injury

Many types of epilepsy are caused by an acquired brain injury, such as stroke or traumatic brain injury (TBI). Complementing our work with genetic models of epilepsy, we’ve also utilized rodent models of acquired epilepsy due to pharmacological (to induce status epilepticus-related brain injury) insults or TBI.  Analogous to findings in the TSC models, we have found evidence for the involvement of the mTOR pathway in epileptogenesis in these models of acquired epilepsy due to brain injury and shown that mTOR inhibition may also have anti-epileptogenic actions in these models. Ongoing studies are investigating downstream mechanisms of epileptogenesis in these models, again with the goal of identifying novel therapeutic targets for acquired epilepsy.

Mechanisms of seizure-induced brain injury

In patients with epilepsy, a significant concern is whether seizures themselves cause brain injury. Seizure-induced brain injury, including both lethal (neuronal cell death) and “non-lethal” mechanisms of cellular injury, could account for cognitive deficits and other neurological co-morbidities that often develop in epilepsy patients. We have studied various pharmacological models of acute seizures and status epilepticus and compared differences in seizure-induced neuronal death in these models, as assayed by conventional histological and novel fluorescent markers of cell death.

We have also utilized modern time-lapse multiphoton imaging methods to directly visualize acute, dramatic structural changes in dendrites and dendritic spines in living mice during seizures in vivo. We have correspondingly found that seizures can activate specific intracellular signaling pathways that lead to breakdown of the normal actin cytoskeleton of dendrites resulting in this “non-lethal” dendritic damage. As dendritic spines normally function in synaptic plasticity and learning, this seizure-induced dendritic injury may represent a mechanistic basis for cognitive dysfunction in epilepsy patients. We have also found that pharmacological stabilization of actin or mTOR inhibition is effective in reducing seizure-induced dendritic injury in mice, thus pointing to a novel therapeutic approach for treating the neurological consequences of epilepsy. Future studies will continue to dissect the mechanisms of seizure-induced brain injury and identify sites for potential therapeutic intervention.