Thymocyte development in the absence of β-/γ-catenin or TCF-1. (A) β-Catenin deletion was induced before transfer as described in the legend to Figure 2. Density plots show gated CD45.2⁺ thymocytes, which were analyzed for CD4/CD8 expression, TCRβ expression among CD8⁺ cells, and the distribution of CD44 and CD25 among lin⁻ thymocytes. Numbers indicate the percentage of cells in the respective quadrant or region. Data show a representative analysis of 5-7 performed using 3 independent β-/γ-catenin donor fetuses after 7 months of reconstitution. The absolute number of control and β-/γ-catenin-deficient (CD45.2⁺) thymocytes was not significantly different. (B) Density plots show a corresponding analysis of thymi from 2- to 3-week-old TCF-1–deficient mice. TCF-1–deficient and control thymi contained 12 (± 7) × 10⁶ and 217 (± 75) × 10⁶ cells, respectively. (C) Survival of β-/γ-catenin–deficient and TCF-1–deficient thymocytes in vitro. Total thymocytes were incubated overnight in complete culture medium without the addition of growth factors. Then cells were surface stained and the presence of viable CD4⁺8⁺ (DP) cells was estimated relative to a fixed number of added microspheres. The ratio of beads to DP cells incubated at 4°C was set to 100%. The bar graph shows the mean percentage (± SD) of surviving DP cells at 37°C. (D) Relative CD4 levels on β-/γ-catenin–deficient and TCF-1–deficient DP thymocytes. The mean fluorescence intensity (MFI) of CD4 staining on DP cells of mutant mice was estimated relative to that of corresponding wild-type controls (100%). The bar graph shows the mean percentage (± SD) of CD4 expression on β-/γ-catenin–deficient (n = 4) or TCF-1–deficient (n = 6) DP cells.