Nonoverlapping functions for Notch1 and Notch3 in thymocyte differentiation. (A) Absolute cellularity in 5 or more thymuses from mice expressing a conditional deletion of Notch1 (N1⁻; Notch1^fl/fl), germline deletion of Notch3 (N3⁻; Notch3^lacZ/lacZ), mice with mutations in both alleles (N1⁻N3⁻), or control mice (N1⁺N3⁺). Note that all mice used for experiments shown in this figure were heterozygous for lck[Cre]. (B-E) CD4/CD8 staining on total thymocytes (right) or CD117/CD25 staining on lineage-negative thymocytes (left) from N1⁺N3^+, N1⁺N3⁻, N1⁻N3⁺, or N1⁻N3⁻ mice, respectively. Both cellularity and phenotype reflect the status of the Notch1 allele, and other than a small decrease in cellularity (similar to that found in N3⁻ mice lacking Lck[Cre], see Figure 2), mutation of Notch3 does not affect the outcome independently of the status of Notch1.