Effect of Tcl1 expression on ES cell growth.

(A) Cell proliferation assay. Cell proliferation between 24 and 48 hours of culture was analyzed by MTT assay. The proliferation rate of Tcl1^−/− (KO) was significantly lower than that of wild-type (WT) or Tcl1^−/−(CAG-Tcl1) cells. Values are expressed as means ± SD (left panel, n = 12 each; right panel, n = 8 each). Difference from Tcl1^−/− (KO) ES cells: ∗∗P<0.01. (B) The percentage of cleaved caspase 3-positive cells was calculated for 9–13 areas selected at random (left panel, n = 9–13, 6312–14211 nuclei per cell line; right panel, n = 10, 3329–4538 nuclei per cell line). The percentage of cleaved caspase 3-positive apoptotic cells in Tcl1^−/− (KO) cells was significantly higher than that in wild-type (WT) or Tcl1^−/−(CAG-Tcl1) cells. Values are expressed as means ± SD. Difference from Tcl1^−/− (KO) ES cells: ∗P<0.05, ∗∗P<0.01. (C) Teratoma formation of wild-type (WT) (n = 9), Tcl1^−/− (KO) #4 (n = 6), Tcl1^−/−(CAG-EGFP) #5 (n = 3), and Tcl1^−/−(CAG-Tcl1) #1 (n = 3) and #3 (n = 5) ES cells. The weight of each teratoma is shown in grams. Horizontal bars indicate the mean of each sample. ∗P<0.03. (D) Histological analysis of the teratomas derived from Tcl1^−/− (KO) #4 and #5 and Tcl1^−/−(CAG-Tcl1) #1 and #3 ES cells. No histological differences were recognizable between Tcl1^−/− (KO) and Tcl1^−/−(CAG-Tcl1) ES cells.