CRYGD and retinitis pigmentosa 1: In this study, we demonstrated that 4-phenylbutyric acid (4-PBA), chemical chaperone, an ER stress inhibitor, dramatically restored downregulation of phototransduction-related genes, CRYGD and F2R, suggesting that ER stress may be a possible therapeutic target for photoreceptor degeneration in EYS-RP patients.