SOS2 and infection: We next evaluated the impact of Sos1 or Sos2 ablation, individually or in combination, on cell cycle status as well as proliferation and survival of steady-state, actively growing primary keratinocytes of the four relevant Sos genotypes that were maintained in 2D-culture dishes after undergoing similar infection in all cases with adenoCre viruses (to discard off-target effects) (Figure 2).