HRD- and βLCR-driven transgenes have distinct expression patterns during terminal erythroid differentiation. (A) Fetal liver cells were grown and switched to differentiation conditions. Nuclear proteins were isolated at the times indicated, and analyzed by Western blot to compare the expression patterns of endogenous Gata1 and the Gata2 protein under the control of HRD and βLCR (line A) transgenes. Top panel: staining of the same blot for Npm1 was used as a loading control. Bottom panel: expression of Gata2 and Gata1 proteins. A higher exposure of the area indicated is shown on the right (B) Graphical representation of the expression levels of the Gata2 and Gata1 proteins after normalization for Npm1 expression. The expression level of HRD-derived Gata2 was determined relative to the Npm1 expression level, and the observed ratio was normalized to 1 at 24 hours of differentiation. The normalization factor was applied to the values obtained for the Gata2/Npm1 ratios at the other time points, for both the HRD-G2 and βLCR-G2 samples. For differentiation time 0 hours and 36 hours, the difference between βLCR-driven Gata factor expression is significantly different from that of endogenous Gata1 (lower, P < .01 and higher, P < .04, respectively [4 independent experiments]). HRD-driven Gata factor expression is not significantly different from endogenous Gata1 at any time point analyzed (unpaired t test).