library_construction_protocol: The frozen hippocampus tissues directly into a prechilled Dounce homogenizer with ice-cold homogenization buffer (0.25 M sucrose, 25 mM KCl, 5 mM MgCl2, 20 mM tricine-KOH [pH 7.8], 1 mM dithiothreitol, 0.15 mM spermine, 0.5 mM spermidine, protease inhibitors, 5 μg/mL actinomycin, 0.32% Nonidet P-40, and 0.04% bovine serum albumin). After 25 strokes with a loose pestle, we mixed the homogenate 1:1 in OptiPrep and centrifuged the solution at 10,000 × g for 20 min at 4 °C. We subsequently collected the separated nuclei, which were pelleted at the bottom of the centrifuge tube, washed them once to remove the OptiPrep, and resuspended them in Dulbecco's modified Eagle medium/F12 supplemented with 10% fetal bovine serum. All buffers and gradient solutions for nuclei extraction contained 60 U/mL RNAsin. The protocol was refered to Shun-Fat Lau, et al, 2020. Library was performed according to the manufacter's instructions(single cell 3' v3 protocol, 10x Genomics).