Cell-intrinsic loss of GPIbα expression on platelets is correlated with the loss of gp96/grp94 and GPIbα expression on megakaryocytes. (A) Top: Flow cytometry of GPIbα expression on platelets (CD41⁺Ter119⁻) from a WT mouse and a KO mouse at the indicated days PTD. The Y-axis is the cell count. The gray histogram represents background staining with isotype-matched antibody. Bottom: Flow cytometry of forward scatter profile (FSC) on platelets (CD41⁺Ter119⁻) at the indicated time points PTD. Data are representative of at least 3 independent experiments. Numbers indicate mean fluorescence intensity for GPIbα and mean size for FSC. (B) Top: Flow cytometry of CD41⁺ expression on Ter119-gated platelets from WT → WT (blue), KO → WT (red), and mixed (WT, blue; KO, red) bone marrow chimeras 1 month PTD. Bottom: GPIbα on WT → WT (blue), KO → WT (red), and mixed (WT, blue; KO, red) bone marrow chimeras from the above gates. Data represent 2 independent experiments with multiple mice. (C) Top: Immunofluorescence of GPIbα expression on megakaryocytes (CD41⁺) of bone sections from WT and KO mice at the indicated time points PTD. Bottom: Immunofluorescence of gp96/grp94 expression on megakaryocytes (CD41⁺) of bone sections from WT and KO mice at the indicated time points PTD. Slides were counterstained with DAPI. Data are representative of at least 3 independent experiments.