FIG 10.

The kinase activity of ERK3 is required for normal thymocyte differentiation. (A) Representative thymic profiles of Erk3^+/+ and Erk3^KA/KA E18.5 mice. The percentages of cells in the different thymocyte subsets are indicated on the dot plot. (B) Cell numbers for the different thymocyte populations are shown for Erk3^+/+ and Erk3^KA/KA E18.5 mice. The bars represent the mean values; each dot corresponds to one mouse. (C) Reduced cell surface expression of the TCR by Erk3^KA/KA DP thymocytes. The representative overlay shows TCRβ cell surface expression by Erk3^+/+ (thin line) and Erk3^KA/KA (thick line) DP thymocytes. (D) Compilation of the percentages of TCR^lo, TCR^int, and TCR^hi DP thymocytes in Erk3^+/+ and Erk3^KA/KA mice. Each dot represents one mouse, and the bars indicate the mean values. Data are representative of 2 independent experiments. ***, P < 0.001, two-tailed Student's t test.