(A) FACS histogram of bone marrow MNC double-labeled for expression of CD34 antigen (FITC) and c-kit receptor (PE). Cells in region R2 are defined as being Kit “bright,” whereas cells in the region labeled R3 are defined as Kit“low.” (B) RT-PCR analysis of FACS isolated cells for Etsand Myb mRNA expression. Molecular weight marker lanes are indicated by ø. Lanes 1 and 2 show Ets-2 mRNA expression, lanes 4 and 5 c-myb expression, and lanes 7 and 8, β-actin expression in Kit “bright” and Kit “dull” cells respectively. Lanes 3, 6, and 9 represent water control lanes for the PCR reactions.