Mouse retinas were homogenized by passing them through a 30-gauge BD 9 http://www.bd.com) needle 5–10 times in 1× PBS solution. Nuclear and cytoplasmic proteins were extracted using the NE-PER Nuclear and Cytoplasmic Extraction Kit (Product# 78833, Pierce Biotechnology, http://www.piercenet.com). Proteins were separated by 10% SDS-PAGE and transferred to nitrocellulose. After blocking overnight at 4 °C in 5% skim milk, membranes were incubated in the primary antibody for 2 h at room temperature. After three 10-min washes in TPBS (100 mM Na2HPO4, 100 mM NaH2PO4, 0.5 N NaCl, 0.1% Tween-20), membranes were incubated for 30 min at room temperature in the secondary horseradish peroxidase-conjugated antibody (Jackson ImmunoResearch Laboratories, http://www.jacksonimmuno.com). Blots were developed using the ECL-Plus chemiluminescent detection system (Amersham Pharmacia Biotech, http://www.pharmacia.ca), according to the manufacturer's instructions.