Symmetric Numb segregation in Numb and dnNb TG DN thymocytes. (A) Confocal images of mitotic Numb TG (top) or dnNb TG (bottom) fetal thymocytes at metaphase, anaphase, and telophase stages stained with antibodies against CD25 (red), Numb (green), and treated with TOPRO-3 iodide (blue). The images are representative of at least 3 independent experiments. (B) Percentage of Numb inherited by each daughter cell at the telophase stage in Numb TG (●) and dnNb TG (▴) mice. A total of 10 (Numb TG mice) and 6 (dnNb TG mice) z-stacks were analyzed. Average standard deviation for DC#1 and DC#2 = 5.11 (Numb TG), 6.22 (dnNb TG). Horizontal lines represent average values. (C) A model of Numb influence on thymocyte decisions.