Platelets from DAPP1^−/−mice are hyperresponsive to GPVI stimulation. (A) FACS analysis of P-selectin exposure on WT and DAPP1^−/− (KO) mouse platelets in response to CRP (10 min). n = 9 + standard error of the mean. (B) ATP release by WT and DAPP1^−/− mouse platelets in response to CRP. Data are expressed as peak ATP release as a percentage of a standard. n = 5 + standard error of the mean. (C) FACS analysis of integrin α_IIbβ₃ activation on WT and DAPP1^−/− mouse platelets in response to CRP (10 min). n = 9 + standard error of the mean. (D) Integrin α_IIbβ₃ activation on WT and DAPP1^−/− mouse platelets in response to CRP (5 µg/mL, 10 min) after preincubation for 10 minutes with either vehicle, WTM (100 nM), or AR-C66069 (ARC, 1 μM). FACS fluorescence intensities (A, C-D) were normalized to the response to maximal agonist concentration averaged per mouse pair (WT and DAPP1 KO) to preserve sample variance at the maximal concentration. Statistical analyses were performed by using 2-way analysis of variance with Bonferroni post-tests. *P < .05; **P < .001; ***P < .0001.