Hoxa-9^-/- marrow has a normal frequency of immunophenotypic HSCs. Normal and Hoxa-9^-/--deficient marrow cells were analyzed by FACS for expression of lineage markers, flk-2, Sca-1, and c-kit. Marrow cells were initially gated for Lin^-flk-2^- cells (left-hand panels). Lin^-flk-2^- cells were then analyzed for expression of Sca-1 and c-kit (middle- and right-hand panels). The frequency of c-kit⁺flk-2^-Lin^-Sca-1⁺ (KFLS) cells in mutant (A) and wild-type (B) marrow was essentially identical (1 in 10 000 nucleated cells).