Figure 2.

Disruption of β3-integrin in platelets and megakaryocytes results in a bleeding phenotype. A) No differences observed in red blood cell (RBC), white blood cell (WBC), or platelet counts in β3KOP (solid bars) vs. TS-HET (hatched bars) and WT mice (open bars). B) Increased gastrointestinal bleeding events in β3KOP mice. Fecal occult blood tests were performed on feces samples from β3KOP and littermate controls and demonstrated a significantly higher number of positive tests in β3KOP mice. *P < 0.01 vs. controls; χ² test. C) Increased bleeding times in β3KOP mice. Each symbol represents bleeding time on a single mouse according to genotype. In each case. bleeding in β3KOP mice had to be stopped by the examiner when bleeding did not stop spontaneously. P < 0.001; ANOVA with appropriate post hoc test. D, E) Platelet aggregation was dysfunctional in β3KOP platelets. D) In vivo clot retraction was assessed using pooled PRP from β3KOP mice and HET control mice. Red blood cells were added to enhance the color contrast for the photograph. E) Platelet aggregation assays on a slide (SPAT) were performed using PRP. No significant platelet aggregation was observed in PRP isolated from β3KOP mice; each test performed ≥3 times/genotype.