The location of the PTC type 1 mutation affects the efficiency of alternative splicing in TAM blast cells. (A) The location of the GATA1 mutation in each TAM patient. Details of the mutation in each sample are described in Table 1. (B) RT-PCR analysis of GATA1 in TAM blast cells harboring PTC type 1 mutations. RT-PCR was performed using primers recognizing both the long transcript including exon 2 and Δexon 2 (top). All of the patient samples consisted of mononuclear cells from peripheral blood. The numbers in parentheses indicate the number of nucleotides in mRNA from the translation initiation codon. Ex 2(+) and Ex 2(−) indicate PCR products with or without exon 2, respectively (middle). Ratio of Ex 2(−)/(+) was calculated from the results of a densitometric analysis of the RT-PCR (bottom). Note that the intense bands of the short form were observed in the samples from the patients who have GATA1 mutations located on the 3′ side of exon 2 (lanes 7-11).