GABA is the major transmitter at inhibitory chemical synapses in the CNS and alterations in type A GABA receptor (GABAR) function have been hypothesized to be a critical component of epileptogenesis. Alterations in GABAR subunit-specific mRNA levels in vivo underlie changes in functional properties of dentate granule cells following pilocarpine-induced status epilepticus (SE). Increased expression of the alpha-4 subunit and decreased expression of alpha-1 after pilocarpine treatment produces benzodiazepine insensitivity and increased zinc blockade of GABA currents. It has long been suspected that a change in the number or composition of GABARs can produce profound changes in inhibitory synaptic transmission, however, it is not known whether the changes in GABAR properties seen in animal models of temporal lobe epilepsy (TIE) are either necessary or sufficient for epileptogenesis. We have shown that the minimal promoter of the alpha-4 subunit gene (GABRA4) when contained within AAV vectors controls region-specific transcription and condition-specific SE up-regulation. In addition, we have shown that viral-mediated delivery of alpha-1 subunits using the GABRA4 promoter inhibits the development of spontaneous seizures, establishing for the first time a connection between the expression of GABAR subunits and epileptogenesis in animals. Results of functional promoter assays and in vivo chromatin immunoprecipitation (ChIP) show that the condition-specific response of the GABRA4 gene most likely reflects the binding of the early growth response factor 3 (EGR3). The experiments of this proposal are aimed at determining the role of prolonged synaptic activity and release of growth factors to Egr mediated changes in GABRA4 transcription that occur in cultured primary embronic and postnatal dentate granule cells. Using viral-mediated delivery of RNAi to target both endogenous Egr3 and GABRA4 gene expression, we will test whether increased alpha-4 subunits are required for development of spontaneous seizures in TLE rats.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
3R01NS050393-03S1
Application #
7676498
Study Section
Molecular Neuropharmacology and Signaling Study Section (MNPS)
Program Officer
Stewart, Randall R
Project Start
2006-04-01
Project End
2011-03-31
Budget Start
2008-04-01
Budget End
2009-03-31
Support Year
3
Fiscal Year
2008
Total Cost
$50,000
Indirect Cost
Name
Boston University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
604483045
City
Boston
State
MA
Country
United States
Zip Code
02118
Scharfman, Helen E; Brooks-Kayal, Amy R (2014) Is plasticity of GABAergic mechanisms relevant to epileptogenesis? Adv Exp Med Biol 813:133-50
Saha, Shamol; Hu, Yinghui; Martin, Stella C et al. (2013) Polycomblike protein PHF1b: a transcriptional sensor for GABA receptor activity. BMC Pharmacol Toxicol 14:37
Grabenstatter, Heidi L; Russek, Shelley J; Brooks-Kayal, Amy R (2012) Molecular pathways controlling inhibitory receptor expression. Epilepsia 53 Suppl 9:71-8
Kim, Julia H; Roberts, Daniel S; Hu, Yinghui et al. (2012) Brain-derived neurotrophic factor uses CREB and Egr3 to regulate NMDA receptor levels in cortical neurons. J Neurochem 120:210-9
Gonzalez, Marco I; Brooks-Kayal, Amy (2011) Altered GABA(A) receptor expression during epileptogenesis. Neurosci Lett 497:218-22
Brooks-Kayal, Amy R; Raol, Yogendra H; Russek, Shelley J (2009) Alteration of epileptogenesis genes. Neurotherapeutics 6:312-8
Hu, Yinghui; Lund, Ingrid V; Gravielle, Maria C et al. (2008) Surface expression of GABAA receptors is transcriptionally controlled by the interplay of cAMP-response element-binding protein and its binding partner inducible cAMP early repressor. J Biol Chem 283:9328-40
Hu, Yinghui; Russek, Shelley J (2008) BDNF and the diseased nervous system: a delicate balance between adaptive and pathological processes of gene regulation. J Neurochem 105:1-17
Reddy, Timothy E; Shakhnovich, Boris E; Roberts, Daniel S et al. (2007) Positional clustering improves computational binding site detection and identifies novel cis-regulatory sites in mammalian GABAA receptor subunit genes. Nucleic Acids Res 35:e20
Roberts, Daniel S; Hu, Yinghui; Lund, Ingrid V et al. (2006) Brain-derived neurotrophic factor (BDNF)-induced synthesis of early growth response factor 3 (Egr3) controls the levels of type A GABA receptor alpha 4 subunits in hippocampal neurons. J Biol Chem 281:29431-5

Showing the most recent 10 out of 11 publications