library_construction_protocol: Cells were washed once with PBS, singularized using TrypLE and resuspended in PBS + 0.5%BSA (FACS buffer) at the concentration of 1x10^6 cells/ml. Approximately 500,000 cells for each sample were pelleted at 500 x g for 5 min at 4℃ and resuspended in 100 μL FACS buffer supplemented with 500 ng of one of four Hashtag Antibodies: A0251 anti-human Hashtag 1 Antibody (Biolegend 394601) for 0 nM RA, A0252 anti-human Hashtag 2 Antibody (Biolegend 394603) for 100 nM RA, A0253 anti-human Hashtag 3 Antibody (Biolegend 394605) for 1 μM RA, A0254 anti-human Hashtag 4 Antibody (Biolegend 394607) for 10 μM RA. Samples were incubated on ice for 30 min and then washed twice with 1 mL of FACS buffer. Cells were pelleted as before and resuspended in 250 μL FACS Buffer. Cells were filtered through 40 μM cell strainers (Fisher Scientific; 22363547) and counted on a hemocytometer. Equal counts of each of the four concentrations were combined and cells were recounted using a hemocytometer.  9,900 cells were used to generate 10X scRNAseq library using Chromium Next GEM Single Cell 3' v3.1 reagents according to manufacturer's instructions (10X Genomics; CG000206 Rev D). Hashtag libraries were prepared according to the manufacturer's protocol (BioLegend). scRNAseq libraries were indexed using 10X SI-GA-B10 and SI-GA-B11 indices and HTO libraries were indexed using D701 (CGAGTAAT) and D702 (TCTCCGGA) indices. Libraries were sequenced on a Nextseq 550 using a High Output v2.5 75-cycle kit (Illumina, 20024906) to a mean read depth of 57,698 and 59,121 reads per cell for the two RNA replicates and 567 and 770 reads per cell for the respective hashtag libraries.