Individual BFU-E but not CFU-GM colonies express EPO. (A) Individual erythroid BFU-E and nonerythroid CFU-GM colonies stimulated with EMP were harvested and analyzed by RT-PCR for EPO, EPOR, and G6PD. BFU-E colonies (lanes 1-4) contain EPO and EPOR mRNAs, and CFU-GM colonies (lanes 5-8) were negative. The housekeeping gene G6PD is expressed in both types of colonies. Size marker 123 bp ladder (M), negative control (−), genomic DNA (g), EPO, EPOR, or G6PD cDNA (+). (B) Restriction digestion analysis. EPO RT-PCR products prepared from individual BFU-E colonies (lanes 2-4) were digested (lanes 6-8) with either PstI (upper panel) or PvuII (lower panel). cDNA EPO template PCR product (lane 1) and its digest (lane 5). A similar restriction pattern in respect to the size of digested DNA (PstI digest, 175, 90, and 23 bp; PvuII digest, 201 and 87 bp) was obtained from all analyzed samples.