Higher CD26 activity, decreased migration, and engraftment potential of TFPI unresponsive GPC3^−/− HSPCs. (A) WT or GPC3^−/− mouse BM-derived KLS cells were cultured in the presence of SCF and Tpo with or without TFPI. After 5 days, the cells were harvested and CD26 enzyme activity was assessed (n = 5). (B) KLS cells from WT, GPC1^−/−, and GPC3^−/− mouse BM were treated with or without TFPI, and migration toward CXCL12 assessed (n = 5). (C) Proportion of transplanted progenitors homed into the recipient BM after 16 hours of transplantation was compared between TFPI-treated and untreated KLS cells from WT and GPC3^−/− mice by Colony forming unit-cell assays (n = 8). (D) A total of 0.5 × 10⁶ BM cells from WT, GPC1^−/−, and GPC3^−/− mice together with 0.5 × 10⁶ competitor CD45.1 BM cells were transplanted in lethally irradiated hosts and donor-derived chimerism in peripheral blood was analyzed after 3 months (n = 12). One million BM cells from primary recipients were injected in lethally irradiated secondary recipients (n = 12). Donor-derived chimerism in secondary recipients was analyzed after 3 months of transplantation. Error bars represent SEM. *§#, P < .05; §, WT vs GPC3^−/−; #, GPC1^−/− vs GPC3^−/−.