Homing defect in Shp2^Δ/Δ BM cells. (A) Competitive reconstitution strategy 2: transplantation first/injection later. The recipient mice were treated with poly-I:C after BM transplantation. (B) Percentage of CD45.2 donor-derived cells using 1:1 donor to competitor ratio with poly-I:C injection after transplantation (n = 4-7). (C) Shp2^Δ/Δ BM contributed significantly less LSK cells in the 1:1 ratio competitive reconstitution experiment (n = 3). (D) Percentage of CD45.2 donor-derived cells within different lineages in 1:1 ratio competitive reconstitution (n = 3). (E) Declined reconstitution efficacy of Shp2^Δ/Δ BM cells in the secondary transplantation (n = 4-6). (F) Sorted LSK cells were used as donor cells in the transplantation first/injection later competitive reconstitution assay. Peripheral chimerism was analyzed at indicated time points (n = 4). (G) In vivo homing assays. Results were shown with percentage of homed BM cells 16 hours after transplantation (n = 4, 5). (H) Homing defects in Shp2^Δ/Δ progenitors. 5 × 10⁶ wild-type or Shp2^Δ/Δ BM cells were transplanted to lethally irradiated mice. Recipient BM was harvested 24 hours later and seeded in Methocult 3434 medium (StemCell Technologies Inc). Colonies were counted on day 8 (n = 7). We used lethally irradiated but nontransplanted recipients as negative control, and no colonies were detected from the BM. Significantly fewer colonies were formed from Shp2^Δ/Δ marrow transplantation, suggesting that the homing defect resides in primitive progenitors. (I) Shp2 deletion severely reduces the chemotactic response of lin⁻ cells to SDF-1α. 10⁶ lineage-depleted BM cells were plated in the upper chamber for migration toward 5 nm SDF-1α in the lower chamber (performed in triplicate). ***P < .001, **P < .01,*P < .05; error bars are SD.