(A) Flow cytometric analysis of the B-cell colonies generated from bone marrow of a transgenic mouse (Tg) and a nontransgenic control (C) with anti-B220 and anti-CD43 antibodies (4 weeks of age). Colonies established from transgenic mice and nontransgenic controls are similarly positive for B220 and show the same broad pattern for CD43. (B) Expression of transgene-derived mRNA in the transgenic B-cell colonies. The RT-PCR products of the transgenic colonies (Tg) and nontransgenic colonies (C) were electrophoresed in an agarose gel, stained with ethidium bromide, and photographed. In the top panel (E2A-HLF), products of genomic and mRNA amplification are indicated by arrows and the position of the DNA size markers are shown on the left. In the bottom panel (K-ras), K-ras RT-PCR products are shown as an internal control.