library_construction_protocol: BM cells were harvested from femurs, tibiae, pelvises and vertebrae by gentle crushing in RPMI medium. Low-density BM mononuclear cells (BMMNCs) were isolated by density gradient centrifugation using Ficoll Histopaque 1083, cells were pooled from all 7 recipients/ group, and stained with an anti-mouse antibody coctail. Donor-derived HSCs (Lin-cKit+Sca1+Flk2-CD48-CD150+) were sorted using MoFlo Astrios Cell Sorter. HSC cells were directly sorted into 50μl RNA extraction buffer and total RNA was extracted according to the manufacturer's protocol  (ARCTURUS PicoPure RNA Isolation Kit). Samples were shipped to BGI. cDNA was amplified from total RNA using the Ovation® RNA‑Seq System V2 at BGI.