VWF/p.V1316M induces ADAM17-independent GPIbα shedding. Quantification of GPIbα (A) and GPIX (B) receptor levels by flow cytometry at the surface of circulating platelets collected from WT-VWF/WT (red bars, n = 26) or WT-VWF/p.V1316M (blue bars, n = 26) mice. (C) Platelet count in ADAM17^fl/flPF4-Cre⁺ mice expressing VWF/WT (100%, n = 4, red diamonds) or VWF/p.V1316M (n = 4, blue diamonds) 4 days after hydrodynamic gene transfer. The right axis shows the absolute platelet count. (D) Platelet size in ADAM17^fl/flPF4-Cre⁺ mice (100%, n = 4, red diamonds) and ADAM17^fl/flPF4-Cre⁺ -VWF/p.V1316M mice (n = 4, blue diamonds). The right axis shows FSC values. (E) Platelet aggregates found in blood smears from ADAM17^fl/flPF4-Cre⁺-VWF/p.V1316M mice. Images were acquired as described in Figure 1. (F) Quantification of GPIbα receptor levels by flow cytometry at the surface of circulating platelets collected from ADAM17^fl/flPF4-Cre⁺-VWF/WT mice (n = 4, lime green bar) and ADAM17^fl/flPF4-Cre⁺-VWF/p.V1316M mice (n = 4, light green bar). (G) Representative immunoblot for glycocalicin (GC; detected with anti-GPIbα antibody Xia.G7 from EMFRET Analytics, Würzburg, Germany) in plasma from WT and ADAM17^fl/flPF4-Cre⁺ mice expressing VWF/WT and VWF/p.V1316M (upper panel). Quantification of data in upper panel using Image Studio Lite software (lower panel); data are mean ± SD. n = 3-9 mice per group. ***P ≤ .001.