Novel molecular mechanisms for Prph2-associated pattern dystrophy.

Area of Science:

• Ophthalmology
• Genetics
• Molecular Biology

Background:

• Mutations in peripherin 2 (PRPH2) are linked to retinitis pigmentosa (RP) and macular dystrophies, but the reasons for varied patient outcomes are unknown.
• Most PRPH2 mutations occur in the D2 loop, crucial for protein folding via disulfide bonds.
• A C213Y mutation causes butterfly-shaped pattern dystrophy, unlike adjacent C214 mutations leading to RP.

Purpose of the Study:

• To investigate the molecular mechanisms underlying the phenotypic variability of PRPH2 mutations.
• To understand how the C213Y mutation affects PRPH2 protein function and interactions.

Main Methods:

• Generated a knockin mouse model expressing the C213Y PRPH2 mutation.
• Assessed PRPH2 protein oligomerization with Rom1 and self-assembly.
• Quantified PRPH2 levels, rod and cone function, and outer segment structure in mutant mice.
• Investigated the effect of wild-type PRPH2 supplementation.

Main Results:

• The C213Y mutant PRPH2 protein failed to oligomerize with Rom1 but could form homotetramers.
• Heterozygous C213Y mice showed reduced PRPH2 levels and impaired rod and cone function.
• Supplementation with wild-type PRPH2 improved protein levels and outer segment structure but did not restore function.

Conclusions:

• PRPH2 mutations can cause retinal disease through mechanisms other than haploinsufficiency, including stable mutant proteins with gain-of-function effects.
• The C213Y mutation leads to distinct molecular defects and functional deficits in retinal cells.
• Therapeutic strategies for PRPH2-associated diseases may require eliminating the mutant protein to be effective.