Date of Award

12-2014

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Biochemistry

Advisor

Wayne N. Frankel

Second Committee Member

Greg Cox

Third Committee Member

Keith Hutchison

Abstract

Epilepsy is characterized by seizures and is one of the most common neurological diseases in the world affecting approximately 3% of the population worldwide [2, 40]. It is estimated that 1 in 10 individuals will have at least one seizure during his/her lifespan [40]. At the onset of this project, only a handful of genes have been identified in causing epilepsy, in part because it is a genetically complex disease [12]. In addition, 1/3rd of all epilepsy patients fail to achieve complete seizure control with the current anti-epileptic drugs (AEDs) and many patients have adverse side effects from the drugs [30]. As a result, further research is needed for the discovery of more epilepsy-associated genes and to understand the mechanism underlying seizures for the development of better therapeutic drug targets. A new mouse mutant was identified in the Neuroscience Mutagenesis Facility (NMF) at The Jackson Laboratory that had a low seizure threshold response to electrical stimuli. Here we describe the gene identification and characterization of this mouse mutant named, Nmf389. We used two high-throughput sequencing techniques, exome and RNA sequencing to identify the mutation causing the low seizure threshold phenotype in these mice. The mutation was located in the Tmem151b gene, a gene with no previously known function, located on Chromosome 17. The mutation was a forty-two nucleotide deletion resulting in an in-frame deletion of fourteen amino acids. We confirmed through a Tmem151b knockout mouse that this was indeed the gene causing the low seizure threshold phenotype in the Nmf389 mutant mouse and proceeded to further characterize the phenotypic and seizure susceptibility. Phenotypically, these mice were normal except they had simpler dendritic processes from the CA pyramidal cells of the hippocampus. We also found that these mice are sensitive to electrically-induced seizures and occasionally older mice exhibit spontaneous seizures. Additionally, we examined if the Nmf389 mutation modified seizures in two known genetic models of epilepsy and found in one that the Nmf389 mutation may suppress the seizure-phenotype. These results show the power in whole genome mutagenesis screen combined with high-throughput sequencing for the discovery of novel seizure-associated genes.

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