p53-independent up-regulation of Noxa in Ptpn11^Δ/Δ HSCs and progenitors. (A) Quantitative PCR of Noxa and Puma in LSKCD150⁺ and LK cells from control and Ptpn11^Δ/Δ mice 23 days after pIpC induction. Results present mean ± SEM relative to Gapdh expression. *P < .05, Student t test. Representative data from one of 4 experiments with similar results are shown. (B) Lin⁻ BM cells, harvested from control and Ptpn11^Δ/Δ mice 10 days after pIpC induction, were infected with control lentivirus or lentivirus expressing a dominant negative p53 mutant (GSE56). Cells were cultured for 48 hours in vitro before staining with anti–c-kit and anti-Sca1 antibodies. GFP⁺ LSK cells were sorted and Noxa expression (mean ± SEM) was determined by quantitative PCR. *P < .05, Student t test. NS indicates not significant. Representative data from one of 3 experiments with similar results are shown. (C) Lin⁻ BM cells were infected with control lentivirus or lentivirus expressing GSE56. Cells were cultured for 48 hours in vitro and were left untreated or irradiated (IR, 300 cGy), harvested, and subjected to quantitative PCR as described in panel B. The levels of Puma and Noxa normalized to Gapdh expression are shown (mean ± SEM). *P < .05, Student t test.