Assessment of TEL/PDGFβR transgene expression: the fusion protein is expressed in tumors and hematopoietic tissues from transgenic mice, but not in tissues from normal controls. (A) PCR of RNA isolated from transgenic and normal mouse tissues. The forward primer (TPY3F, 5′-TAC AAA AAG TAC CAG CAG-3′) binds the 3′ end of the PDGFβR, and the reverse primer (HBG1, 5′-GCG AGC TTA GTG ATA CTT GT-3′) anneals to the antisense strand of the human β-globin exon 3 and were designed to span the β-globin intron in the transgenic construct (see Fig 2). Samples contaminated with genomic DNA give a larger, 1.6-kb product (data not shown). The 0.7-kb product expected from the amplification of spliced mRNA is seen in samples isolated from transgenic mouse tumor, spleen, and bone marrow, but not in normal spleen, bone marrow, or in reverse transcriptase–negative controls. (B) Western blot of whole-cell lysates from tumors (N), bone marrow (M), and kidney (K). The antibody used was tail PDGFβR. The TEL/PDGFβR protein runs as a doublet, as reported previously,10 due to an alternate start site for translation within the TEL gene.