GpIb-mediated growth arrest is followed by apoptosis. The Y-axis is the mean fluorescence of FITC-conjugated Annexin V (which binds to phosphatidylserine exposed during apoptosis) and the X-axis is a log scale of cell number. Flow cytometry for Annexin V-binding cells was performed 48 hours after serum repletion. The population of CHO cells expressing /β/IX shows increased annexin V binding in comparison to control cells (vector/β/IX). This is reversed by expressing a mutant complex with a truncation of its 14-3-3 interaction domain (594/β/IX). A mutant with a deleted actin binding protein domain (del/β/IX) continues to show an increased number of apoptotic cells 48 hours after serum-repletion (n = 2).