Inhibition of stromal cell heparan sulfate synthesis promotes HSPC egress from the BM and accumulation in extramedullary sites. (A-C) PB analysis showing (A) the WBC count; (B) the contribution to B cells (B220), myeloid cells (Mac1 and Gr1), and T cells (CD3); and (C) the number of circulating progenitor cells measured by CFU assay in methylcellulose in chimeric mice. (D-F) Spleen analysis showing (D) total weight, (E) the contribution to KLS CD48⁻CD150⁺ HSCs, and (F) the contribution to CMP, GMP, and MEP cells. (G-H) Spleen-resident KLS CD48⁻ CD150⁺ HSCs analysis showing (G) cell cycle analysis; cells in G0, G1, and S-G2-M phases of the cell cycle are shown, as well as (H) apoptosis in control and mutant chimeric mice. (I) Relative PB reconstitution and (J) contribution to B cells (B220), myeloid cells (Mac1 and Gr1), and T cells (CD3), 16 weeks after transplantation, of recipient C57BL/6J (CD45.2) mice transfused with spleen cells from control or mutant chimeric mice (CD45.1) competed with equal numbers of wild-type (WT) CD45.2 spleen cells. (K) Representative 3-dimensional micro-computed tomography images of femoral cortical bone (top) and cancellous bone (bottom) of control and mutant chimeric mice. Data are representative of at Ctrl, control; KO, knockout.