The details of the microinjection were as follows: Mice were anesthetized with isoflurane and prepared for aseptic surgery by shaving the dorsal surface of the skull and applying a chlorhexidine-based surgical scrub. Ophthalmic ointment was applied to each eye and the mouse was then transferred to and positioned on a stereotaxic frame (David-Kopf Instruments, Tujunga, CA). A 1-cm midline incision was made in the skin over the dorsal surface of the skull, and the skull was exposed to allow the positioning of a drill over the Bregma point of reference. From Bregma, the coordinates used were + 1 mm anteroposterior, + 1.7 mm lateral, and − 3 mm ventral to the skull surface. These coordinates were selected to target the center of the left striatum and avoid passing through any ventricle. 10% brain homogenates were injected with Nanofil syringes (World Precision Instruments, Sarasota, FL) and steel bevel needles (33-gauge diameter for Q226X and G131V and 26-gauge diameter for the Y226X brain homogenate) into the striatum at a rate of 0.5 μl/min with a total of 1.0 μl per mouse controlled with a pump (UltraMicroPump III with a Micro4 pump controller; World Precision Instruments). The needle was kept in place for 2 min following injection to avoid any reflux of the brain homogenate (BH) solution. The skin incision was closed with sutures. The patency of the needles was verified prior to and after injections. Following surgery mice were placed on a heating pad until fully recovered.