ERG

Five 20-day-old mice were anesthetized and each underwent an intravitreal injection with 1 μL rAAV1-dCasX-KRAB/sgRNA-mPK5 as described above. After 2 weeks, ERG (by dark adaptation, using a DIAGNOSYS Celeris containing an interior stimulator) was performed as followed. After overnight dark adaptation, the animals were prepared for ERG recording under dim red light. While under anesthesia with a mixture of ketamine 1% pentobarbital sodium (10 mg/kg i.p.), their pupils were dilated using one drop of 1% tropicamide followed by one drop of 1% cyclopentolate hydrochloride applied on the corneal surface. One drop of Genteal (corneal lubricant) was applied to the cornea of the untreated eye to prevent dehydratation. A drop of 0.9% sterile saline was applied on the cornea of the treated eye to prevent dehydration and to allow electrical contact with the recording electrode. The binocular stimulators were aimed at both eyes of the mouse, and the impedance was less than 10 Ω. A series of flash intensities was produced by the stimulators to test both scotopic and photopic response.⁴¹