Restoration of thymocyte development and β-selection associated proliferation in Lck-Cre Fbx12fl/fl mice by deletion of Cdkn1b. (a) Flow cytometry of cells from Thymus (left) or Spleen (right) from mice of the indicated genotype. Thymus: left, CD4 vs CD8 staining of total thymocytes; center, CD44 vs CD25 staining of lineage-negative DN thymocytes. Spleen: CD4 vs CD8 staining of total splenocytes. (b) Cell numbers of the indicated thymocyte subsets and DN3/DN4 ratio (n=4 mice per genotype). (c) Percentage of cycling S/G2/M stage cells in the indicated thymocyte subsets determined by staining for DAPI vs Ki-67 (n=4 mice per genotype). For all graphs, horizontal lines indicate the mean and vertical lines indicate the standard deviation (±s.d.), P values were determined by unpaired two-tailed Student’s t-test. NS, not significant (P>0.05), *P<0.05, **P<0.01, ***P<0.005, ****P<0.0001. Data shown in (a) are representative of four independent experiments.