Investigating the pathogenicity of missense mutations in VSX1 and their association with corneal dystrophies

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Litke_Anastasia_MSc_2018.pdf (3.52 MB)

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2018-05-04

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Litke, Anastasia Marie

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Abstract

Two corneal dystrophies, posterior polymorphous corneal dystrophy (PPCD) and keratoconus, have been associated with missense mutations found in the transcription factor-encoding gene Visual System Homeobox 1 (VSX1). Despite this association, the pathogenic link between VSX1 and these diseases remains controversial. To address this issue, I utilized a variety of in vitro approaches to study how seven VSX1 missense mutations found in disease populations that span two highly conserved domains, the homeodomain (HD) and CVC domain affect VSX1 transcriptional activity, protein expression levels and subcellular localization. I also carried out an in vivo investigation by generating a mouse line carrying a mutation in Vsx1: P254R. Corneal morphology was examined through histology and ex vivo whole eye confocal imaging which was used to assess corneal thickness. Quantification of immunocytochemistry was used to characterize terminal marker expression in the inner retina compared to previously described phenotypes in Vsx1-null mice. My in vitro results showed that mutations found in both the HD and CVC domain alter the normal transcriptional repression activity in Vsx1. These changes were not due to changes to protein expression or subcellular localization. Characterization of corneal and retinal phenotypes in vivo revealed no significant differences in Vsx1 P254R mice when compared to wild-type and Vsx1-null controls. In conclusion, my work shows that Vsx1 P254R is not pathogenic for corneal dystrophies in a mouse model. However, my in vitro studies show that Vsx1 mutations have the ability to alter transcriptional activity and therefore still have the potential to be pathogenic in humans. Further investigation is needed to determine whether VSX1 mutations found in disease populations are, in fact, causative for corneal dystrophies.

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corneal dystrophy, cornea, PPCD, keratoconus, posterior polymorphous corneal dystrophy, confocal

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http://hdl.handle.net/1828/9342

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ETD (Electronic Theses and Dissertations)
Theses (Biology)
 
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