Gata1 is essential for the stress erythropoietic response. (A) Peripheral blood counts of the Tx-treated Gata1^fl/y::Tx-Cre (KO-Tx) (■) and WT mice (□) after induction of hemolytic anemia with PHZ. Results are shown as mean plus or minus SD (error bars); n ≥ 3. RBC indicates red blood cell counts; HCT, hematocrit; PLT, platelet counts. Bottom graph displays the RBC volume of representative WT and KO-Tx samples. (B) Plasma Epo levels of KO-Tx (●) and WT (○) mice after induction of hemolytic anemia with PHZ. Epo values are plotted against HCT values for each mouse. (C) Log₁₀ (Epo)/HCT ratios after PHZ treatment. Average and SD are shown; n ≥ 4. (D) BM sections (hematoxylin and eosin staining) and cytospins (Wright-Giemsa staining) of KO-Tx and WT mice after induction of hemolytic anemia with PHZ. (E) Spleens and Wright-Giemsa staining of cytospins from splenic cells of KO-Tx and WT mice after PHZ treatment. (F) CFUe assays of BM and spleen cells of KO-Tx and WT mice after induction of hemolytic anemia with PHZ.