Coexpression of SCL and the c-Kit receptor in hematopoietic precursors.

(A) Bone marrow cells from wildtype (WT) andSCL^lacZ/w knock-in mice were stained with lineage markers (B220, Mac-1, TER119) and the c-Kit antibody, while the SCL locus activity was revealed by β-galactosidase staining with the fluorogenic substrate FDG. Left panels show the c-Kit receptor and FDG fluorescence in the lineage-negative population. Right panels show lineage markers and FDG fluorescence. Results are representative of 3 independent experiments. (B) High c-Kit levels correlate with strong FDG staining. Within the lineage-negative compartment, FDG fluorescence was analyzed in c-Kit^high, c-Kit^int, and c-Kit^neg populations. The MFIs of FDG staining on sorted SCL^lacZ/wt bone marrow cells are indicated (thick line). FDG staining on WT bone marrow (thin line) was used as a negative control. Dead cells were excluded from analysis by propidium iodide staining. Results are representative of 3 independent experiments. (C) SCL and c-kit are coexpressed during B-cell differentiation. Bone marrow B-cell precursors from wild-type mice were purified by flow cytometry31 and gene expression was investigated by RT-PCR. Levels of interleukin receptor 7α (IL-7Rα) were determined to confirm the developmental stages of purified B cells, and S16 was used as a control for the amount of cDNA.