library_construction_protocol: Animals were sedated with ketamine and xylazine and perfused with a minimum of 25 mL of PBS. 2-3 brain stems were pooled as one sample. Brain stems were cut into pieces and digested for 40 min at 37 °C with 5% CO2 in PBS supplemented with 1mg/mL Collagenase 1 (Roche), 10U/mL Pulmozyme (Dornase alpha) and 3.423 mg/mL Trehalose (Sigma Aldrich). 20 μl of sterile EDTA was added to each sample and incubated at 37°C for another 5 min. Tissues were then mechanically disrupted through a 70 μm cell strainer into a single-cell suspension. Single-cell suspensions were washed with 25 mL 2% FCS-HBSS (Thermo Fisher Scientific), centrifuged, and resuspended in a mixture of PBS with 0.5% BSA (VWR) and Debris Removal Solution (Miltenyi Biotec). After overlaying PBS with 0.5% BSA, suspensions were centrifuged, resuspended, and adjust the cell count to 106 cells/mL. Single cell suspensions were converted to barcoded scRNAseq libraries following the manufacturer's instructions. Quality control of libraries were performed with Tapestation 4200. After QC.