After removing the cerebellum, forebrains (hemispheres) were put into RNase-free RINOTM tubes (#PINKR1-RNA, Next Advance, NY) filled with 1ml of RLT lysis buffer (RNeasy® mini kit, Qiagen) and homogenized with Bullet Blender (Next Advance). After a brief centrifuge, 100µl of homogenates were diluted into 400µl of RLT buffer. After mixing with 500µl of 70% EtOH, total RNA was isolated according to the manufacturer's protocol (RNeasy® mini kit, Qiagen). Messenger RNA was purified from total RNA using poly-T oligo-attached magnetic beads. The library was prepared with NEBNext Ultra II RNA library preparation kit.