A Y178C rhodopsin mutation causes aggregation and comparatively severe retinal degeneration

Area of Science:

• Molecular Biology
• Neuroscience
• Genetics

Background:

• Rhodopsin mutations lead to autosomal dominant retinitis pigmentosa, a degenerative retinal disease.
• The precise mechanisms of photoreceptor cell death and the role of rhodopsin aggregation remain unclear.
• Previous studies linked in vitro aggregation severity to in vivo retinal degeneration rates for P23H and G188R mutants.

Purpose of the Study:

• To investigate the Y178C rhodopsin mutant to determine if the in vitro-in vivo aggregation-degeneration relationship holds true for other misfolding mutations.
• To compare the pathogenic effects of the Y178C mutant with previously studied rhodopsin mutants (P23H, G188R).

Main Methods:

• In vitro characterization of Y178C rhodopsin mutant in HEK293 cells, assessing mislocalization and aggregation.
• In vivo studies in mice to evaluate the impact of Y178C rhodopsin expression on retinal degeneration.
• Utilized PROTEOSTAT dye to label and morphologically analyze rhodopsin aggregates in vivo.

Main Results:

• Y178C rhodopsin mutant mislocalized to the endoplasmic reticulum and formed aggregates in vitro, similar to G188R.
• In vivo, Y178C rhodopsin induced more severe retinal degeneration than G188R, despite similar aggregate morphology.
• Photoreceptor cell death in Y178C mice occurred significantly independently of PROTEOSTAT-labeled aggregates, unlike in P23H and G188R.

Conclusions:

• The Y178C rhodopsin mutation causes severe retinal degeneration, with cell death pathways extending beyond PROTEOSTAT-detectable aggregates.
• PROTEOSTAT-labeled aggregates are not the sole contributors to photoreceptor cell death in Y178C-induced retinitis pigmentosa.
• Alternate forms of rhodopsin aggregates or other pathogenic mechanisms may be involved in Y178C-mediated retinal degeneration.