Hematopoietic characterization of Hox mutants. FL cellularity (left panel) from 13.5-, 14.5-, and 15.5-day-old wild-type embryos and from homozygous and heterozygous Hoxb4 and Hoxb1-Hoxb9 14.5-day-old embryos (n = 6, 22, 8, 19, 20, 17, and 10 from left to right). P values are .01, .03, and < .001 for FL cellularity of Hoxb4^-/-, Hoxb1-b9^+/-, and Hoxb1-b9^-/- mice, respectively. Myeloid progenitors per fetal liver (center panel, n = 3, 4, 3, 3, and 3) and per 3000 sorted c-kit⁺ cells (right panel, n = 3) of E14.5 mutant and control FLs. Values are expressed as the mean ± SD from 3 samples per test group (exact number shown in Tables 1 and 2). Statistical analysis was performed using a 2-tailed Student t test.