Enforced TAL1 expression enhances SRC activity. (A) Secondary transplantations were performed by intravenous injection of total bone marrow cells containing 2 to 2.5 × 10⁶ human CD45⁺ cells (39 mice, white symbols) or of purified human CD34⁺ cells (6 mice, black symbols) from primary mice. Secondary mice were analyzed at 5 to 6 weeks (45 mice, 3 experiments) and at 12 weeks after transplantation (14 mice, 1 experiment). Shown are the levels of engraftment measured by the percentage of CD45⁺ cells achieved in secondary recipients. Median values are indicated. A positive mouse contained at least 0.1% human cells in its BM. (B) Phenotype analysis of the human cells detected in 2 representative secondary recipients analyzed 5 weeks after transplantation. Percentage of positive cells is indicated in each quadrant for every surface marker tested. (C) TAL1 transgene expression in human CD45⁺ cells enriched from the bone marrow of 3 secondary recipients that received BM cells from primary mice that received a transplant 5 weeks before with TAL1⁺ cells.