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PURPOSE: As part of a large scale systematic screen to determine the effects of gene knockout mutations in mice, a retinal phenotype was found in mice lacking the Slc9a8 gene, encoding the sodium/hydrogen ion exchange protein NHE8. We aimed to characterize the mutant phenotype and the role of sodium/hydrogen ion exchange in retinal function. METHODS: Detailed histology characterized the pathological consequences of Slc9a8 mutation, and retinal function was assessed by electroretinography (ERG). A conditional allele was used to identify the cells in which NHE8 function is critical for retinal function, and mutant cells analyzed for the effect of the mutation on endosomes. RESULTS: Histology of mutant retinas reveals a separation of photoreceptors from the RPE and infiltration by macrophages. There is a small reduction in photoreceptor length and a mislocalization of visual pigments. The ERG testing reveals a deficit in rod and cone pathway function. The RPE shows abnormal morphology, and mutation of Slc9a8 in only RPE cells recapitulates the mutant phenotype. The NHE8 protein localizes to endosomes, and mutant cells have much smaller recycling endosomes. CONCLUSIONS: The NHE8 protein is required in the RPE to maintain correct regulation of endosomal volume and/or pH which is essential for the cellular integrity and subsequent function of RPE.

Original publication

DOI

10.1167/iovs.14-15735

Type

Journal article

Journal

Invest Ophthalmol Vis Sci

Publication Date

05/2015

Volume

56

Pages

3015 - 3026

Keywords

Animals, Cell Culture Techniques, Disease Models, Animal, Electroretinography, Fluorescent Antibody Technique, Gene Knockout Techniques, Gene Silencing, Intraocular Pressure, Mice, Mice, Inbred C57BL, Microscopy, Confocal, Mutation, Ophthalmoscopy, Plasmids, Real-Time Polymerase Chain Reaction, Retinal Diseases, Retinal Pigment Epithelium, Sodium-Hydrogen Exchangers