Constitutive SLAP expression interferes with Epo-induced survival and BCL-X induction. (A) Quantitative evaluation of apoptosis by TUNEL assay in EpoR and EpoR/SLAP erythroblast clones maintained in the presence of Epo for 24 hours (left panel) or 48 hours (right panel). The mean and standard deviation of 3 independent fields are shown. (B) RT-PCR analyses of BCL-x mRNA expression in EpoR and EpoR/SLAP erythroblasts that were maintained as in panel A. PCR was carried out by using primers specific for either the chicken BCL-x gene (top blot) or the S17 gene as normalization control (bottom blot). Aliquots of 0.5 μL, 1 μL, and 2 μL of each RT product were used. The expected 667-bp BCL-x fragment and 80-bp S17 gene fragment are indicated.