Northern blot analysis of M1 clonal lines transfected with the GATA-1 expression vector. Lane 1, parental M1 cells; lane 2, M1 cells transfected with the control vector; lane 3, M1GATA-Y1 clone; lane 4, M1GATA-Y22 clone; lane 5, M1GATA-Y25 clone; lane 6, EL-4 murine thymoma cell line. The membrane containing 15 μg total RNA from each cell line was sequentially hybridized with murine GATA-1, murine GATA-2, NF-E2 (p45), Maf K, murine CD34, human platelet factor 4 (hPF 4), murine β-globin, and 18S rRNA probes.