Epilepsy Mutations in Different Regions of the Nav1.2 Channel Cause Distinct Biophysical Effects

dc.contributor.advisorCummins, Theodore
dc.contributor.authorMason, Emily R.
dc.contributor.otherSullivan, William J., Jr.
dc.contributor.otherBrustovetsky, Nickolay
dc.contributor.otherSheets, Patrick
dc.contributor.otherHashino, Eri
dc.date.accessioned2020-07-07T14:32:47Z
dc.date.available2020-07-07T14:32:47Z
dc.date.issued2020-06
dc.degree.date2020en_US
dc.degree.disciplinePharmacology & Toxicology
dc.degree.grantorIndiana Universityen_US
dc.degree.levelPh.D.en_US
dc.descriptionIndiana University-Purdue University Indianapolis (IUPUI)en_US
dc.description.abstractWhile most cases of epilepsy respond well to common antiepileptic drugs, many genetically-driven epilepsies are refractory to conventional antiepileptic drugs. Over 250 mutations in the Nav1.2 gene (SCN2A) have been implicated in otherwise idiopathic cases of epilepsy, many of which are refractory to traditional antiepileptic drugs. Few of these mutations have been studied in vitro to determine their biophysical effects on the channels, which could reveal why the effects of some are refractory to traditional antiepileptic drugs. The goal of this dissertation was to characterize multiple epilepsy mutations in the SCN2A gene, which I hypothesized would have distinct biophysical effects on the channel’s function. I used patch-clamp electrophysiology to determine the biophysical effects of three SCN2A epilepsy mutations (R1882Q, R853Q, and L835F). Wild-type (WT) or mutant human SCN2A cDNAs were expressed in human embryonic kidney (HEK) cells and subjected to a panel of electrophysiological assays. I predicted that the net effect of each of these mutations was enhancement of channel function; my results regarding the L835F and R1882Q mutations supported this hypothesis. Both mutations enhance persistent current, and R1882Q also impairs fast inactivation. However, examination of the same parameters for the R853Q mutation suggested a decrease of channel function. I hypothesized that the R853Q mutation creates a gating pore in the channel structure through which sodium leaks into the cell when the channel is in its resting conformation. This hypothesis was supported by electrophysiological data from Xenopus oocytes, which showed a significant voltage-dependent leak current at negative potentials when they expressed the R853Q mutant channels. This was absent in oocytes expressing WT channels. Overall, these results suggest that individual mutations in the SCN2A gene generate epilepsy via distinct biophysical effects that may require novel and/or tailored pharmacotherapies for effective management.en_US
dc.identifier.urihttps://hdl.handle.net/1805/23195
dc.identifier.urihttp://dx.doi.org/10.7912/C2/341
dc.language.isoen_USen_US
dc.subjectelectrophysiologyen_US
dc.subjectepilepsyen_US
dc.subjectmutationsen_US
dc.subjectNav1.2en_US
dc.subjectvoltage-gated sodium channelsen_US
dc.titleEpilepsy Mutations in Different Regions of the Nav1.2 Channel Cause Distinct Biophysical Effectsen_US
dc.typeThesis
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