Impact of Grin1 deletion on platelet and MK spreading on either a collagen or fibrinogen matrix. (A-B) Morphology of MKs from Pf4-Grin1^−/− and WT mice spread on glass coverslips coated with collagen. (A) Representative images of MKs stained for F-actin (red), α-tubulin (green), and Hoechst 33342 nuclear counterstain (blue). Red arrows indicate examples of F-actin nodules frequent in WT but not Pf4-Grin1^−/− MKs. Green arrowheads point to the α-tubulin coil often maintained in Pf4-Grin1^−/− MKs. (B) Bar graphs showing cell area (i), cell circularity (ii), F-actin nodule density per cell area (μm²) (iii), and numbers of F-actin nodules per cell (iv), quantified from fluorescence images shown in panel A using ImageJ. (C) Morphology of platelets from Pf4-Grin1^−/− and WT mice spread on glass coverslips coated with fibrinogen. (C) Representative images of platelets activated with either 10 μM of ADP (i-ii) or 0.1 U/mL of thrombin (iii-iv) and stained for F-actin (red) and α-tubulin (green); red arrows point to F-actin nodules common in WT but not Pf4-Grin1^−/− platelets (i-ii); green arrowheads point to deformed, collapsed, and centralized α-tubulin coil, and red arrowheads indicate peripheral stress fibers of F-actin (iv), both more frequent in WT but not Pf4-Grin1^−/− platelets (iii); green arrows indicate partially maintained peripheral α-tubulin coil in Pf4-Grin1^−/− platelets (iv). For panels A and C, 2 independent experiments were performed with a total of 5 biologic replicates per group. For panel B, 35 MKs were analyzed per group. All bar graphs show median ± 95% CI. Statistical significance is shown (Mann-Whitney U test).