PCR amplification from cDNA and FISH.

(A) Multiplex PCR. Lane 1 = case #1, lane 2 = case #2, lane 3 = e13a2-positive patient, lane 4 = K562 cell line (e14a2 positive), lane 5 = SD1 cell line (e1a2 positive), lane 6 = “blank.” Note the faint band of approximately 500 bp (arrow) and the 800-bp band corresponding to BCR(arrowhead). (B) PCR with primers corresponding to BCR exon e1 and ABL exon a3. Lane 1 = case #1, lane 2 = case #2, lane 3 = SD1 cell line, lane 4 = “blank.” Sequencing of the 540-bp PCR product (arrow) revealed 51 bp ofBCR intron 1 (nt 75253-75302, accession U07000) fused between e1 and a3. (C) PCR with primers corresponding to BCRexon e1 and ABL exon a2. Lane 1 = case #1, lane 2 = case #2, lane 3 = SD1 cell line, lane 4 = “blank.” M indicates molecular weight marker. (D) FISH (LSI bcr/abl probe, Vysis, Downer's Grove, IL). Left panel (case #1): two yellow fusion signals (arrowheads) indicate an m-BCR rearrangement. Right panel: one yellow fusion signal (arrow) indicates an M-BCRrearrangement (patient with confirmed e13a2 transcript).