Increased number of apoptotic cells is observed in c-Maf^−/− fetal liver. (A) Gross appearance of E13.5 fetal liver. The c-Maf^−/− fetal liver is smaller than a c-Maf^+/+ fetal liver. Scale bar represents 100 μm. The picture was taken with a NIKON coolpix 5200 digital camera in macro mode and processed with the Adobe Photoshop CS4 software.(B) The mean total number of fetal liver cells in c-Maf^+/+ (n = 14) and c-Maf^−/− (n = 10) embryos at E13.5, c-Maf^+/+ (n = 6) and c-Maf^−/− (n = 4) embryos at E14.5, and c-Maf^+/+ (n = 8) and c-Maf^−/− (n = 8) embryos at E15.5. The mean number of fetal liver cells is significantly reduced in c-Maf^−/− embryos. Data are presented as mean ± SEM. (C) H&D staining of c-Maf^+/− and c-Maf^−/− fetal liver sections (top). Arrowheads indicate pyknotic nuclei, which indicate apoptotic cells. TUNEL assays showed increased apoptosis in the c-Maf^−/− fetal liver (bottom panel). Images were acquired by a Leica DM RXA2 microscope (Lecia HC PL Fluotar 20×/0.50 PH2) at room temperature and processed with the Adobe Photoshop CS4 software. Scale bars in the top panel represent 200 μm. Scale bars in the bottom panel represent 50 μm. (D) The fraction of cells in different phases of the cell cycle was measured by PI staining followed by flow cytometric analyses. The percentage of cells in sub-G₀/G₁, G₁, S phase, and G₂/M are indicated. The sub-G₀/G₁ phase represents the apoptotic population. The apoptotic population was increased in c-Maf^−/− fetal liver.