Characterization of Eng cKO mice. (A) Scheme for pIpC treatment. To induce Eng deletion, Engfl/Δ;Mx1-Cre+ mice (blue) and control mice (red), Engfl/wt;Mx1-Cre+ or Engfl/Δ;Mx1-Cre−, were injected intraperitoneally with 5 doses of pIpC (250 µg) every other day for 10 days. (B-D) Eng deletion in HSCs. BM from pIpC-treated control mice (left panels) and Engfl/Δ;Mx1-Cre+ mice (right panels) were analyzed by fluorescence-activated cell sorting (FACS) 2 weeks after the last pIpC injection. (B) Representative gating strategy for the LSKCD48−CD150+ HSC fraction are showed in the top 3 rows. Control LSKCD48−CD150+ HSCs are homogenously positive for Eng (bottom left panel), whereas HSCs from pIpC-treated Engfl/Δ;Mx1-Cre+ mice have significantly reduced levels of this receptor (bottom right panel). Representative histogram plots (C) and respective quantification (D) confirm Eng deletion in HSCs from pIpC-treated Engfl/Δ;Mx1-Cre+ mice, whereas HSCs from controls express Eng at very high levels. (D) Box plot whiskers represent minimum and maximum values for each cohort (n = 5 per group). (E-G) Blood counts. Time course analyses of white blood cells (WBC) (E), red blood cells (RBC) (F), and platelets (PLT) (G) in pIpC-treated Engfl/Δ;Mx1-Cre+ mice and control mice. Error bars represent standard error of the mean for each cohort (n = 8 per group). (H) Survival curve shows that Eng deletion does not affect the survival rate of pIpC-treated Engfl/Δ;Mx1-Cre+ mice compared with controls. A total of 14 mice was analyzed (7 for each group). Mice were followed for a total of 30 weeks. ***P < .001.