Abstract
Purpose :
Arrestin and glial fibrillary acidic protein (GFAP) are expressed in photoreceptors and Müller cells, respectively, and play an important role in phototransduction. Harmonin is a scaffolding protein involved in the development and function of ciliated cells including photoreceptors and inner ear hair cells; however, its role in the retina remains unclear. Mutations in harmonin lead to Usher syndrome (Usher), the most common genetic cause of deaf-blindness. Acadian Usher Type 1C is attributed to the USH1C c.216G>A splicing mutation, and knock-in mice display severe hearing impairment, balance disturbances, and visual dysfunction similar to patients. To understand the effects of the 216A mutation on protein expression in the retina, we performed quantitative discovery-based proteomics of retinal extracts from wild type (WT), Usher, and 216A-targeted antisense oligonucleotide (ASO)-treated Usher mice. We hypothesize that Usher retinas have abnormal Arrestin and GFAP protein expression compared with WT controls. Furthermore, we predict that ASO treatment, which improves Ush1c expression and restores visual function in Usher mice, also restores normal Arrestin and GFAP expression in the retina.
Methods :
Juvenile Usher mice were treated with 216A-ASOs by intravitreal injection (IVI) and allowed to recover for 2.5 months post-IVI. Visual function was measured in ASO-Usher, Usher, and WT mice at 3 months of age using electroretinogram (ERG) analysis. Retinas were then harvested and processed for proteomic analysis using liquid chromatography and mass spectrometry (LCMS) and confirmed with immunohistochemistry (IHC) and western blot analysis.
Results :
ERGs were significantly increased in ASO-Usher mice compared with untreated Usher controls. LCMS identified significantly differentially expressed proteins in WT versus Usher (155/3659) and ASO-Usher versus untreated Usher (124/3663) retinas. Among these, Arrestin levels were significantly decreased and GFAP levels were significantly increased in Usher retinas compared to WT. Expression levels were significantly improved following ASO treatment as measured by LCMS, IHC, and western blot analyses.
Conclusions :
These data demonstrate that ASO treatment improves visual function in Usher mice, as well as restores WT Arrestin and GFAP expression levels in the retina, suggesting a new role for harmonin in the healthy retina.
This is a 2021 ARVO Annual Meeting abstract.