Reduced pluripotent progenitor numbers and clonogenic potential in Pbx1^−/− FL.

(A) Representative FACS profiles of wt (left) andPbx1^−/−(right) FL at E14.5 show a relative increase in frequency of lin⁻Sca-1⁺c-Kit⁺ cells inPbx1^−/−FL. Note that the absolute numbers of lin⁻Sca-1⁺c-Kit⁺AA4.1⁺cells per FL, however, are reduced (wt = 2.8 × 10⁴cells per FL; Pbx1^−/−= 1.6 × 10⁴ cells per FL). Results are shown for single animals of each genotype. (B) In vitro clonogenic potential is shown for HSC-enriched pluripotent progenitors, which were purified by 2 rounds of FACS analysis of cells from 4 pooled FLs of each genotype by means of the FACS gates shown in panel A. (C) Day-8 CFU-S frequency for purified Pbx1^−/−andPbx1^+/−lin⁻Sca-1⁺c-Kit⁺ cells injected into irradiated wt recipients. Data were obtained from a single experiment (representative of 2) on cells (with 4 or more pooled FLs of each genotype) purified by 2 rounds of FACS sorting by means of the gates shown in panel A.