Qualitative effects of Ap2a2-transduced HSCs. (A) Cell proliferation counts of respective green fluorescent protein–positive (GFP⁺) transduced cells. *P = .03. Values presented are means ± SEM from independent experiments for pKOF (n = 3), pAp2a2 (n = 4), HoxB4 (n = 4), and NA10HD (n = 2). (B) Methylcellulose assays for in vitro proliferation and differentiation. Values presented are means ± SEM number of GFP positive colonies from 3 independent experiments. Statistical significance between vector and Ap2a2 for CFU-G, *P < .001; CFU-GEMM, *P = .02; and BFU-E, *P = .002. (C) Cytospin morphology of respective GFP⁺-transduced cells. Asterisks indicate clusters of undifferentiated blasts. (D) Means ± SEM from 300 cell differential counts with respective GFP⁺-transduced cells from independent experiments for vector (n = 5), pAp2a2 (n = 5), and NA10HD (n = 2). Statistical significance between vector and Ap2a2 was P = .002 and for NA10HD, *P ≤ .0001). (E) Quantitative RT-PCR expressed as G₀:cycling ratio (mean ± SEM) from LT-HSC (CD49b⁻Rho^lowLSK) and IT-HSC (CD49b⁺Rho^lowLSK) populations paired for G₀-quiescent and cycling from 7 independent sorts. Both Ccnb1 (Cyclin B1) as part of the cell-cycle network⁶  and Gpsm2, which is involved in active mitotic spindle orientation,^8-10  serve as effective internal controls given their (expected) relative higher expression during cycling (see also supplemental Figure 2C).