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Michael Stuck, Shannon Conley, Muna Naash; A novel knock-in model for the Y141C pattern dystrophy mutation in RDS. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5087.
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© ARVO (1962-2015); The Authors (2016-present)
Mutations in the photoreceptor specific retinal degeneration slow (RDS) gene have been linked to pattern dystrophy (PD) and macular dystrophy/choroidal neovascularization (MD/CNV) in patients. PD is a complex genetic disorder which involves multiple genetic loci; however the cellular and molecular mechanisms which lead to PD in many cases are unknown. Of particular interest is why some RDS mutations cause PD/MD while others cause retinitis pigmentosa (RP). Here we study a known PD/MD associated RDS mutation (Y141C) to understand the biochemical and cellular changes that accompany the disease process.
We generated a Y141C-RDS knock-in model and used a heterologous expression system (transiently transfected Cos-7 cells) to study the effects of the Y141C mutation in RDS. RDS complex formation and protein localization were analyzed both in vitro and in vivo. Retinal function, structure and ultrastructure were assessed in vivo by electroretinography (ERG), histology/electron microscopy, fundus imaging, and fluorescein angiography.
In vitro studies demonstrated that Y141C-RDS protein aggregates and fails to oligomerize normally. RDSY141C/Y141C knock-in mice exhibited normal RDS mRNA levels but protein levels were low and exhibited signs of aggregation. Outer segments (OSs) in the RDSY141C/Y141C were dysmorphic and significantly shorter than normal, but Y141C protein was targeted correctly to the OSs. Scotopic and photopic amplitudes from knock-in mice are consistent with Y141C being a loss-of-function mutation: RDSY141C/+ mice show haploinsufficiency phenotype comparable to RDS+/- while RDSY141C/Y141C is similar to RDS-/-.
We show that Y141C-RDS does not form proper RDS complexes and is not capable of supporting OS formation. These data indicate that Y141C is a loss-of-function mutation so it is not clear why the patient phenotype is PD/MD/CNV rather than RP as has been seen with other loss-of-function mutations (e.g. C214S). Studies are ongoing to see if the Y141C mice develop the PD fundus phenotype or CNV, but these preliminary results suggest that development of PD may require additional mutations or genetic modifiers and that studying the mechanisms underlying RDS-associated PD/MD will be difficult in monogenic disease models.
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