Effects of Runx1-tg on the growth and expansion of thymocytes. (a) Incorporation of bromodeoxyuridine (BrdU) into various subsets of thymocytes. Lck-Cre-tg mice (open boxes) and distal Runx1-tg;Lck-Cre-tg mice (closed boxes) were each injected with BrdU intraperitoneally. Thymocytes were prepared after 4 hr and processed for flow cytometric analysis of BrdU, CD4/CD8, CD25 and CD44. Percentages of BrdU+ cells in various subsets are shown as the mean ± SD values (n = 3). Significances of difference were statistically tested by Student’s t-test, and if detected between the compared genotypes, they are indicated by brackets with *(P < 0·05). (b) Ontogeny of DN and DP thymocytes during mouse development. Thymuses were taken from mice at embryonic day 17·5 (E17.5), E18.5, at birth, 1, 2 and 6 weeks after birth, and processed for flow cytometric analysis of CD4 and CD8 expression. The numbers of total, DN and DP cells are shown in distal Runx1-tg;Lck-Cre-tg (thick lines) and Lck-Cre-tg mice (thin lines).