IL2RG and severe combined immunodeficiency: To evaluate the role of WASp during in vivo differentiation, WT, WASp KO, and IL2RG-CRISPRed HSPCs were transplanted into 3-day-old sublethally irradiated immunodeficient non-obese diabetic–severe combined immunodeficiency (SCID) Il2RG−/− (NSG) pups.