Generation of mice conditionally lacking Mcl-1 expression in neutrophils and macrophages. (A) Schematic of targeting strategy for Mcl-1 allele. E1, E2, and E3 are exons 1-3 of Mcl-1. S indicates SpeI site. The size of alleles digested by SpeI and the probe are shown. (B) Southern blot analysis of gDNA from homologously recombined ES clones and parental ES cells (wild type). gDNA was digested with SpeI and hybridized with probes shown in panel A. (C) Southern blot analysis of gDNA from the tails of Mcl-1^f/+ mice after crossing with FLPeR mice. gDNA from wild-type mice (+/+) served as a control for the wild-type allele. (D) Expression of Mcl-1 in BM-derived macrophages. Macrophages derived from 1-week culture of BM from Mcl-1^−/− and control mice in the presence of L929-conditioned medium were lysed for Western blot analysis. Erk expression serves as a loading control.