Platelet spreading on immobilized fibrinogen. Washed platelets were layered at a density of 5 × 10⁷/mL onto fibrinogen-coated slides. After several time points, cells were fixed and incubated with the membrane stain, vybrant DiO. Platelets lacking either PLCβ2β3 or PI3Kγ had impaired spreading compared with wild-type platelets. The spreading defect was most apparent at earlier time points. This demonstrates that second messengers generated by both PLCβ2β3 and PI3Kγ are required for platelet spreading. Results are representative for 3 experiments performed to date.