GFI1B and anemia: Consequently, numbers of reticulocytes (Retic), immature reticulocytes (IRF-H) and macrocytic RBCs (Macro) were increased in the absence of Gfi1b as well as the mean corpuscular volume (MCV) and red cell size and shape (RDW), while the white blood cell count (WBC) did not change significantly (Figure 2C), indicating that Gfi1b deficient mice suffer from anemia.