Genetic Regulation of Complex Neurological Disease

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DESCRIPTION (provided by applicant): The goal of this Competitive Revision application (NOT-OD-09-058 - NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications) is to complement our current program (NS061971) to study the molecular basis of complex seizure disorder in Brunol4 mutant mice, by examining the cellular basis of the seizure phenotypes using conditional gene expression and electrophysiology. We already published that Brunol4 heterozygous mutants have limbic and tonic-clonic seizures and a low seizure threshold, and homozygous mutants also have spontaneous absence seizures. Using temporal conditional deletion, we recently determined that it is sufficient to delete Brunol4 at 7 wks of age to lower seizure threshold and to produce spontaneous limbic and tonic-clonic convulsions. This was invaluable information to have as it suggests that future investigation into the biological mechanism can focus on adult, maintenance functions of Brunol4 rather than development per se. In addition, by using spatial conditional deletion, we also determined that removing of Brunol4 from cortical and hippocampal excitatory neurons may account for a portion, but not all, of the convulsive seizure phenotype-providing further biological insight into the complexity. In the first part of the competitive revision, we will complete the conditional studies by examining the effects of deleting Brunol4 from inhibitory neurons. We will also assess the effects of compound conditional deletion by combining two different cre drivers (i.e. excitatory and inhibitory). In the second part, we will perform patch-clamp electrophysiological recordings of neurons in germline and conditional mutants, to give further insight into effect of the mutation on synaptic activity at the cellular level. This will be in collaboration with our colleague Dr. Zhang, an expert in brain slice electrophysiology. This extension of the currently funded program, in which the aims are entirely molecular in nature, will complete our initial picture of the 'biology' of the complex seizure disorder in this animal model. In addition, we are excited about the possibility of using this as an opportunity to add new tools to our research abilities. These will be critical both for rounding-out the Brunol4 program, and for providing opportunities for mechanistic insight into our other disease models in the future. PUBLIC HEALTH RELEVANCE: The most common medical conditions, such as heart disease, cancer, autoimmune and brain disorders, are often genetically complex, influenced by the interaction of multiple genes with other factors such as diet and environment. This complexity makes it a challenge to study and to understand the causes of common disease. In this program we will study the function of a gene, called Brunol4, which mimics a genetically complex "excitability" disorder of the brain by causing the misexpression of many other genes. Learning how Brunol4 functions at the molecular and cellular level will help us to understand how and why genes are coordinately regulated in the brain and may provide new entry points for future therapies.