Gene knockout in highly purified mouse hematopoietic stem cells by CRISPR/Cas9 technology

The CRISPR/Cas9 system has been used for genome editing of human and mouse cells. In this study, we established a protocol for gene knockout (KO) in mouse hematopoietic stem cells (HSCs). HSCs were highly purified from the bone marrow of tamoxifen-treated Cas9-EGFP/Cre-ER transgenic mice, maintained in serum-free polyvinyl alcohol culture with cytokines, lentivirally transduced with sgRNA-Crimson, and transplanted into lethally irradiated mice with competitor cells. Previous studies of Pax5 KO mice have shown B cell differentiation block. To verify our KO HSC strategy, we deleted Pax5 gene in 600 CD201⁺CD150⁺CD48^-c-Kit⁺Sca-1⁺Lin^- cells (HSC1 cells), highly enriched in myeloid-biased HSCs, and CD201⁺CD150^-CD48^- c-Kit⁺Sca-1⁺Lin^- cells (HSC2 cells), highly enriched in lymphoid-biased HSCs. As predicted, both Pax5 KO HSC1 and HSC2 cells showed few B cells in the peripheral blood and the accumulation of pro-B cells in the bone marrow of recipient mice. Our data suggesetd that myeloid-biased and lymphoid-biased HSCs share a common B cell differentiation pathway. This population-specific KO strategy will find its applications for gene editing in a varity of somatic cells, particuarly rare stem and progenitor cells from different tissues.