Reconstituting SPL^−/− mice with the SPL S94D variant results a loss of function in platelet aggregation. (A) Schematic of the constructs used to express SPL(WT)-GFP, SPL(S94D)-GFP, or GFP alone. LTR, long terminal repeat; pA, polyadenylation signal. (B) Immunoblot of SPL (top) and GFP (bottom) in platelet lysate derived either from SPL^−/− mice or from lethally irradiated mice reconstituted with SPL^−/− fetal liver cells expressing SPL(WT)-GFP, SPL(S94D)-GFP, or GFP alone. The experiment is representative of 2 similar experiments. (C) Histogram of SPL(WT)-GFP and SPL(S94D)-GFP expression in platelets. The experiment is representative 2 similar experiments. (D) Platelet aggregation stimulated with PAR4 agonist peptide, AYPGKF. Three experiments are summarized in the graph.