RIAM deficiency does not affect platelet outside-in signaling and in vivo thrombus formation. RIAM-null platelets display a normal (A) spreading and (B) reorganization of the actin (red, Phalloidin Atto647N) and tubulin (green, α-tubulin-Alexa F488) cytoskeleton on a fibrinogen-coated (100 μg mL⁻¹) surface. Values in A represent mean. Images in B were acquired with a TCS SP5 confocal microscope (100×/1.4 oil STED objective; Leica Microsystems). Scale bars represent 3 µm. (C-D) Platelet clot retraction of RIAM-null platelets was indistinguishable from wild-type controls. Values in D are mean ± standard deviation. In vivo, RIAM deficiency neither interfered with (E) normal hemostasis as assessed by a tail bleeding time assay nor with (F-G) arterial thrombus formation upon FeCl₃-induced damage of the endothelium. Each symbol in E represents 1 individual. Each symbol in F represents 1 mesenteric arteriole. Horizontal lines in E and F represent mean. Arterioles in G were visualized with an Axiovert 200 inverted microscope and a 10×/0.25 objective (Zeiss). The presented results are representative of ≥3 independent experiments with at least n = 3 vs 3 individuals per group.