Integration and expression of the nls-LacZ gene in multilineage cells. (A) The nls-LacZ gene expressing BM cells recovered 4 weeks after injection. Cells with lymphoid (lower right) and myeloid (upper left) morphology are β-gal⁺. Note the nuclear localization of the β-gal signal. (Original magnification, × 200). (B) Macroscopic view of β-gal⁺ colonies derived from BM cells recovered 4 weeks after injection. The nls-LacZ expressing HPP-CFC and LPP-CFC are evident in a 60-mm culture dish. (C) Microscopic view of one of the nls-LacZ–expressing HPP-CFC shown in (B). (Original magnification, × 5). (D) The nls-LacZ–expressing thymocytes. Approximately 10% of the cells express nls-LacZ in this sample obtained 8 weeks after injection. (Original magnification, × 200). (E) Southern blot of genomic PCR products from FACS-sorted cell populations. Both CD19⁺ B cells and CD33⁺ myeloid cells isolated from a BM 14 weeks after injection (Experiment 11, C2 shown in Table 5) showed strong bands of 470 bp size. In thymocytes recovered 11 weeks after injection, faint bands can be detected in the CD4⁺CD8⁺ and CD4⁺CD8⁻ subsets, but not in the CD4⁻CD8⁺ subset. Reanalysis of sorted cells showed a purity of 99.8% for CD19⁺ cells, 99.5% for CD33⁺ cells, 99.0% for CD4⁺CD8⁺ cells, 99.4% for CD4⁺CD8⁻ cells, and 98.9% for CD4⁻CD8⁺ cells.