Loss of CXCR4 abolishes the effects of Gprasp1 or Gprasp2 silencing on HSPCs.Cxcr4^+/+ or Cxcr4^Δ/Δ HSPCs transduced with Gprasp1, Gprasp2, or control shRNAs were assayed by flow cytometry for apoptosis, cell-cycle status (A), or migration assays toward an SDF-1 gradient in trans-well assays (B). (C) Cxcr4^+/+ or Cxcr4^Δ/Δ CD45.2⁺ LSK cells were transduced with control or Gprasp shRNAs and transplanted with CD45.1⁺ LSK cells into irradiated recipients at a 2:1 ratio. Recipients’ PB was analyzed for CD45.2⁺mCherry⁺ cells. Data in panel C from ≥2 independent transplants with 5 recipients per condition per transplant. Data represented as mean plus or minus SEM. */#, P < .05; **/##, P < .005; ***/###, P < .001 significantly different to control. In panel C, * refers to Gprasp1 shRNA; # refers to Gprasp2 shRNA.