Reduced LPP-CFC/HPP-CFC frequency and proliferation of p85α^-/- and p85α^-/-; p85β^+/- c-kit⁺ fetal liver cells. c-kit⁺ cells were purified from WT, p85β^+/-, p85α^-/-, and p85α^-/-p85β^+/- fetal livers and plated in agar cultures containing growth factors that promote the growth of (A) LPP-CFCs and (B) HPP-CFCs. Data shown are the mean number of colonies per 4000 c-kit⁺ cells plated. ^*P < .05; n = 4. (C) Representative LPP-CFC photomicrographs generated from WT and p85α^-/-; p85β^+/- c-kit⁺ cells. Original magnification, × 40. (D) Proliferation of WT, p85β^+/-, p85α^-/-, and p85α^-/-p85β^+/- c-kit⁺ fetal liver cells in response to kitL. Freshly isolated c-kit⁺ fetal liver cells were plated in triplicate with no growth factors or 10 ng/mL KitL for 16 hours. Cells were pulsed with tritiated thymidine and harvested for measurement of β emission. Results represent the mean thymidine incorporation ± SEM of 9 independent experiments. ^*P < .05. (E) Akt activation of WT, p85β^+/-, p85α^-/-, and p85α^-/-p85β^+/- c-kit⁺ fetal liver cells in response to kitL. Western blots for Akt phosphorylation and total Akt are shown. Data are representative of 4 independent experiments. ^**P < .05 for p85α^-/- vs p85α^-/-p85β-/-.