library_construction_protocol: P7 C57BL/6J and β2KO mice were anesthetized in an isoflurane induction chamber and euthanized by decapitation. All the solutions were filtered using 0.22 µm syringe filter (Fisher #9720511). Eyes were enucleated and retinas were immediately dissected in oxygenated (95% oxygen/5% carbon dioxide) Ames' media with L-glutamine and sodium bicarbonate (pH ~7.4) at room temperature under light scope. Retinas (6 to 8 per sample) were digested for 10 min at 37oC in 70 µl papain (Fisher #LS003126) + 50 µl DNase (Sigma #D4527-40KU) + 50 µl L-cysteine (Sigma #C1276-10G) in 5 ml Ames, which was activated at 37oC for 15 min. Samples were gently swirled once during this incubation. Following this, papain was removed and samples was gently triturated with P1000 pipette tips in 1 ml 10x ovomucoid (Fisher #NC9931428) + 50 µl DNase + 9 ml Ames. Manual trituration was performed using 2 ml of ovo solution at a time and the supernatant was filtered using 40 μm cell strainer in a new tube. This cell suspension was spun down at 450 g for 8 min. Supernatant was discarded and the pellet was resuspended in 250 μl of Ames + bovine serum albumin (BSA). This solution was prepared using 27 ml Ames + 3 ml 4% BSA (Sigma #A9418-5G) + 50 µl DNase. Cells were counted using hemocytometer (1:100 dilution factor with trypan blue). 10 million cells were incubated in 10 µl CD90.2 microbeads (Miltenyi Biotec #130-121-278) for 10 min at 4oC. Following incubation, 6 ml Ames + BSA solution was added and cells were spun down at 450 g for 8 min. Supernatant was discarded and cells were resuspended in fresh 500 µl Ames + BSA solution. Cell suspension was subjected to magnetic-activated cell sorting (MACS) using large cell columns (Miltenyi Biotec #130-042-202) to sort RGCs. To obtain a high number of RGCs, the tube containing the cells was washed with 500 µl Ames + BSA solution for 2 times. To obtain better purity, MACS was repeated one more time on eluted CD90.2+ RGCs using fresh columns. This cell suspension was spun down at 450 g for 8 min and the supernatant was removed. Pellet obtained was resuspended in ~1000 μl of Ames + BSA and cell concentration was counted using hemocytometer (dilution factor 2). This spun down strategy was employed to obtain a highly concentrated sample in a small volume of ~100 μl Ames + BSA. Single-cell libraries on RGCs isolated were prepared using Chromium Next GEM Single Cell 3' Kit v3.1 (10X Genomics, Pleasanton, CA) following manufacturer's protocol.