Investigating the Pathogenicity of VSX1 Missense Mutations and Their Association With Corneal Disease

Abstract

PURPOSE. Despite numerous studies associating Visual System Homeobox 1 (VSX1), with posterior polymorphous corneal dystrophy and keratoconus, its role in these diseases is unclear. Here we examine the pathogenicity of VSX1 missense mutations in vitro and in a mouse genetic model. METHODS.Vsx1 transcriptional repressor activity, protein stability, and subcellular localization activity, was examined using luciferase reporter-based assays, western blotting and immunolabeling, respectively, in transfected human embryonic kidney 293T cells. A genetic model for VSX1 p.P247R was generated to investigate pathogenicity of the mutation, in vivo. A wholemount confocal imaging approach on unfixed intact eyes was developed to examine corneal morphology, curvature, and thickness. Immunolabeling and electroretinography was used to examine retinal phenotype. RESULTS.A mutation corresponding to human VSX1 p.P247R led to enhanced transcriptional repressor activity, in vitro. A mouse model for VSX1 p.P247R did not have any observable corneal defect, but did exhibit an abnormal electroretinogram response characterized by a more prominent ON as opposed to OFF panretinal responsiveness. In vitro analysis of additional VSX1 missense mutations showed that they either enhanced repressor activity or did not alter activity. CONCLUSIONS.Our results indicate that although VSX1 sequence variants can alter transcriptional activity, in the context of a mouse genetic model, at least one of these changes does not lead to corneal abnormalities. While we cannot exclude a role for VSX1 as a risk factor for corneal disease, on its own, it does not appear to play a major causative role.

Atypical visual processing in a mouse model of autism

“…Retinal function was studied electrophysiologically using the full field ERG, following established methods 31 , 37 . In brief, male BTBR (n = 7) and control B6 (n = 6) mice were dark-adapted overnight and prepared under dim red light for ERG recordings (Fig.…”

High VSX1 expression promotes the aggressiveness of clear cell renal cell carcinoma by transcriptionally regulating FKBP10

“…Recent studies reported that VSX1 mutations played a pathogenic role in posterior polymorphous corneal dystrophy [ 32 , 33 ], and that the variant p.(His244Arg) in the VSX1 gene was observed in a sporadic female patient with bilateral keratoconus [ 34 ]. However, there are limited investigations focusing on the relationship between VSX1 upregulation and tumor aggressiveness.…”

Inherited Eye Diseases with Retinal Manifestations through the Eyes of Homeobox Genes

“…Mice lacking Vsx1 exhibit ERG b-wave defects, decreased OFF visual signaling, and a perturbation of directional selectivity, all of which are thought to arise from dysfunctional cone bipolar cell signaling [298,300]. A mouse model for Vsx1 p.P247R did not have any corneal defects, but did exhibit an abnormal electroretinogram response [305].…”

“…The mutations in the homeodomain and critical CVC domain of the VSX1 gene result in abnormal craniofacial features, absence of the roof of the sella turcica, and anomalous development of the corneal endothelium. This mutation also impacts the maintenance of cone bipolar cells of the visual system [304,305]. Nonetheless, the VSX1 gene has not been definitively demonstrated to play a causal role in keratoconus [306,307].…”