Vav1-cre–induced homozygous Mof loss leads to lethal hematopoietic failure in mouse pups. (A) Survival curve of Vav1-cre;Mof^f/f and Vav1-cre;Mof^f/+ mice represented as days after birth (x-axis). (B) Representative photographs of 9-day-old Vav1-cre;Mof^f/f, Vav1-cre;Mof^f/+, and Mof^f/f pups. (C) Representative photographs of spleen, thymus, and liver of 9-day-old Vav1-cre;Mof^f/f, Vav1-cre;Mof^f/+, and Mof^f/f pups. Colors of arrows correlate to mouse genotype (Vav1-cre-Mof^f/f, orange; Vav1-cre-Mof^f/+, mustard green; Mof^f/f, blue). (D) White blood cell (WBC) count, hemoglobin (Hb), and platelet count at time of euthanasia (at 8-9 days of age). (E) BM cell count after CD45.2 selection. (F) Bar graphs representing the total number of mature B cells (B220⁺), myeloid cells (GR1⁺/MAC1⁺), and T cells (CD3⁺) in BM (harvested from femurs, pelvic bones, tibias, and spine) and spleen as measured by FACS. (G) Bar graph representing the total number of MP and LSK cells in BM as measured by FACS. Error bars represent standard deviation (SD) of the mean. Significance is shown for comparing Vav1-cre;Mof^f/f and Vav1-cre;Mof^f/+ to Mof^f/f. *P < .05; **P < .01.