Each retina was dissected from the eyecup after removal of the cornea and lens. Both retinas of each animal were pooled. Total retinal RNA extraction was performed using a combination of reagent (TRIzol; Invitrogen Life Technologies, Carlsbad, CA) and a micro kit (RNAqueous; Ambion, Foster City, CA). The reagent was used to isolate the RNA, and the kit was used to purify and DNase-treat the RNA. Each retina was quickly placed into a 1.5-mL tube containing 200 μL reagent. After the homogenization of retinas on ice, another 660 μL reagent (TRIzol; Invitrogen Life Technologies) and 160 μL chloroform were added to the tube. The tube was vortexed for 20 seconds and allowed to stand for 7 minutes at room temperature. The tubes were centrifuged at 13,000g for 10 minutes at 4°C. The supernatant was then removed and placed into a clean 1.5-mL tube with half its volume of 100% ethanol. The tube was vortexed briefly before contents underwent purification and DNase treatment, as detailed in the micro kit manual ((RNAqueous; Ambion). Purified DNAse-treated RNA was analyzed on a spectrophotometer (ND-1000; NanoDrop Technologies, Wilmington, DE) and a bioanalyzer (2100 Bioanalyzer; Agilent Technologies, Santa Clara, CA) to determine the quantity and quality of the sample. First-strand cDNA synthesis was achieved by reverse transcribing 1 μg total RNA using the reverse transcriptase protocol (Superscript III; Invitrogen Life Technologies, Carlsbad, CA). A cocktail of 1 μL oligo primer, 1 μL 10 mM dNTP, 4 μL 5× RT buffer, 1 μL 0.1 M dithiothreitol, 1 μL 40 U/μL ribonuclease inhibitor (RNaseOut; Invitrogen Life Technologies), and 1 μL reverse transcriptase (Superscript III; Invitrogen Life Technologies) was added to 1 μg retinal RNA and made up to 20 μL with RNase-free water. The mixture was incubated at 50°C for 1 hour before the reaction was terminated by increasing the temperature to 70°C for 15 minutes.