Figure 4.

Response of TKO and control MEFs to cell–cell contact and low serum conditions. (A) Cell cycle analysis of confluent TKO and control MEFs. One or two representative results are shown for each genotype. The percentage of cells in the S phase of the cell cycle is indicated, with standard deviations (+/−). At least three experiments were performed. (B) Cell cycle analysis of confluent TKO and control MEFs in 0.1% serum. The percentages of cells in the S phase of the cell cycle are indicated, with standard deviations (+/−). At least three experiments were performed. “TKO” represents an experiment where all the cells, attached to the plate or floating, were included in the assay. No S-phase count was calculated in these conditions given the high sub-G₁ population. Control cells were analyzed in the same way. “TKO (attached)” corresponds to an experiment where floating cells were removed before cell cycle analysis. (C) Western blot analysis of the cleaved form of PARP specific of apoptotic cells in confluent TKO and control cells grown in 0.1% serum. Extracts were prepared from whole populations, including dead, floating cells. (D) Survival of confluent MEF populations grown in 0.1% serum. Annexin negative and positive cell populations were sorted by flow cytometry, and annexin negative cells were considered to be alive. Percentages are the average of at least three experiments, with standard deviations (error bars).