Cdc42GAP deletion leads to JNK activation and increased apoptosis of HSPs. HSPs were cultured in the presence or absence of 10 μM JNK inhibitor SP600125 and were starved for 6 hours. Cells were stimulated with 100 ng/mL SCF for 10 minutes before they were subjected to Western blot analysis (A) or were analyzed for apoptosis by annexin-V- and 7-AAD-based FACS at different time points (B). (C) JNK siRNA-expressing retrovirus or the control retrovirus-treated HSPs were selected with puromycin (2 μg/mL) for 2 days to enrich the transduced cell population before they were subjected to apoptosis analysis.