Scl/p210;Rac2^−/− LSCs fail to outcompete with wild-type HSCs during competitive repopulation in vivo. (A) Evolution of peripheral blood chimerism of CD45.2⁺ Scl/p210 or Scl/p210;Rac2^−/− splenocytes, competitively transplanted with CD45.1⁺ WT BM cells, into lethally-irradiated CD45.1⁺ mice. Data represent mean ± SD (n = 8 mice per group). (B) Scl/p210-transgenic chimera in peripheral blood of WT recipient mice after 6 weeks of competitive transplantation as determined by genomic DNA b3a2 content of peripheral blood leukocytes. Data represent mean ± SD (n = 8 mice per group). (C-D) Colony-forming unit–cell (CFU-C) homing of Scl/p210 and Scl/p210;Rac2^−/− splenic progenitors into lethally-irradiated recipients (C) BM and to (D) spleen in vivo (n = 3 mice per group); P = n.s; not significant). (E) Adhesion to recombinant fibronectin (CH-296) and (F) migration toward CXCL12 of Non-Tg, Non-Tg;Rac2^−/−, Scl/p210 and Scl/p210;Rac2^−/− hematopoietic progenitors in vitro. Data (mean ± SD) represent 1 of the 2 independent experiments performed each per triplicate of pools of 5 mice per group and experiment. *P < .05, **P = .01, and ***P < .005 between the respective groups.