AMPA glutamate receptors mediate the majority of fast excitatory neurotransmission in the brain. Four AMPA receptor subunits exist, GluR1-GluR4, with functional channels containing various combinations of these four subunits. In hippocampal and cortical pyramidal neurons, AMPA receptors are comprised largely of GluR1/GluR2 and GluR2/GluR3 heteromeric tetramers. Dysregulation of AMPA receptor expression has been reported in many neurological disorders, including epilepsy. AMPA receptors are alternatively spliced, with the best-characterized splice variants being the flip and flop isoforms. AMPA receptors containing flip vs. flop cassettes have distinct channel properties. GluR1 flip and flop variants have similar kinetics, but the flip isoform shows greater sensitivity to glutamate, increasing synaptic gain. Expression of flip channels is associated with greater vulnerability to excitotoxicity and hyperexcitability. Increases in GluR1 flip to flop ratio in hippocampus and cortex are found in epileptic tissue in humans and animal models and may contribute to development of epilepsy (epileptogenesis) and seizure susceptibility. Thus normalizing aberrant splicing represents a novel therapeutic strategy for preventing epileptogenesis. Splice modulating oligonucleotides (SMOs) have unique chemistries and distinct advantages over classic antisense oligonucleotides and siRNA, and are in clinical trials for treating muscular dystrophy and spinal muscular atrophy. We have developed an SMO that specifically and potently reduces GluR1 flip in vivo. We have also shown that knockdown of GluR1 flip with its selective SMO protects against seizures in a neonatal epilepsy model and can prevent post-seizure hyperexcitability associated with epileptogenesis. The goals of this application are to continue to test our novel SMO in mouse models of epileptogenesis in both neonates and adults, to determine if it protects against development of chronic seizures and their deleterious cognitive comorbidities. Our studies are the first to target modulation of alternative splicing as a therapeutic approach for preventing the development of epilepsy, a critical unmet need. Further, our approach represents a new platform technology in epilepsy therapeutics that is applicable to many additional gene targets.
In spite of the recent large increase in the number of drugs available to treat epilepsy, there are no drugs in clinical use that prevent the development of this disease in vulnerable populations. We have developed a novel compound that acts at the level of gene transcription to normalize excitability in the epileptic brain and prevents changes in the brain associated with the development of epilepsy. Our proposed research is designed to validate this compound as a drug for preventing epilepsy in both infants and adults.