Single-cell RNA seq library is prepared with Chromium Next GEM Single Cell 3' Reagent Kits V3.1 (Dual Index) from 10X Genomics according to manufacturer's instruction. Briefly, single HSCs were sorted by FACS into PBS solution. Then microfluids was used to construct droplets containing single-cell, GEMs and reverse transcription reagents. 100 µl of droplets were incubated at 53°C for 45 minutes, then at 85°C for 5 min. Droplets were then released by Recovery Agent, cleaned up with Dynabeads MyOne SILANE and amplified by PCR for 12 cycles. The amplified cDNA was used for library construction according to the manufacturer's instruction.