c-Maf^−/− embryos are anemic. (A) Gross appearance of E13.5 embryos. The c-Maf^−/− embryo is paler and smaller than its c-Maf^+/+ littermate. Scale bar represents 5 mm. The picture was taken with a NIKON coolpix 5200 digital camera in macro mode and processed with the Adobe Photoshop CS4 software. (B) Hematocrit values for c-Maf^+/+ (n = 6) and c-Maf^−/− (n = 6) embryos at E13.5, c-Maf^+/+ (n = 8) and c-Maf^−/− (n = 7) embryos at E14.5, and c-Maf^+/+ (n = 12) and c-Maf^−/− (n = 9) embryos at E15.5. Data are presented as mean ± SEM. The mean hematocrit values for c-Maf^−/− embryos were significantly lower than values for c-Maf^+/+ at E13.5, E14.5, and E15.5. (C) Blood smears from E13.5 embryos stained with May-Grünwald-Giemsa stain. The blood smear from a c-Maf^−/− embryo contains far fewer enucleated red blood cells. Images were acquired by a Biorevo BZ microscope (Plan Apo 20×0.75 DIC N2) at room temperature and processed with the Adobe Photoshop CS4 software. Scale bars represent 20 μm. (D) The percentage of enucleated red blood cells in peripheral blood for c-Maf^+/+ (n = 5) and c-Maf^−/− (n = 7) embryos at E13.5, c-Maf^+/+ (n = 4) and c-Maf^−/− (n = 4) embryos at E14.5, and c-Maf^+/+ (n = 8) and c-Maf^−/− (n = 8) embryos at E15.5. A minimum of 200 cells was counted for each sample. Data are presented as mean ± SEM. The percentage of enucleated red blood cells is significantly reduced in c-Maf^−/− embryos than in c-Maf^+/+ embryos at E13.5, E14.5, and E15.5. *P < .05 and **P < .01.