Yeast two-hybrid screening and GAL4 assay
We carried out yeast two-hybrid experiments using the MATCHMAKER GAL4 two-hybrid system 3 (BD Bioscience) as recommended by the manufacturer. We cloned the full-length mr-s into the pGBKT7 vector and used it to screen a library of mouse P0-P3 retinal cDNAs in the pGADT7 vector. Transformants that conferred growth were picked, isolated and re-introduced with the bait into AH109 to confirm interaction. Plasmid DNA was isolated from yeast using RPM Yeast Plasmid Isolation Kit (Qbiogene). In order to confirm the protein interactions, single colonies were picked and grown individually in synthetic complete media lacking leucine, tryptophan and containing X-gal. After 4–5 days, X-gal positive clones were selected and analyzed. To test self-interaction of mr-s, we subcloned the full-length, N-terminus (amino acids 1–400) and C-terminus (amino acids 391–542) of mr-s into pGBKT7 and pGADT7 vectors. We assessed interactions by scoring blue color on plates of medium containing X-gal.