Using the Pf4-Cre:Confetti system to determine the origin of Mk membrane buds. (A) Schematic representation of the Pf4-Cre:Confetti system used to label Mks for identification of Confetti configurations a–d. (B) Quantification of Confetti configurations of E13.5 circulating Plts by flow cytometry (n = 20 mice). (C) MEFs derived from R26R-Confetti embryos were treated with recombinant TAT-Cre protein and purified by flow cytometry according to fluorescent protein expression. Anti-GFP antibody effectively detected nGFP, cYFP, and mCFP, and anti-RFP detected cRFP (n = 2 independent experiments). Scale bar, 30 μm. (D) With the exception of CFP, these antibodies effectively identified Pf4-Cre:Confetti configurations for Mks in high-volume 3D imaging of E13.5 FL: cassette 1 expression shown in blue; cassette 2 expression in yellow; coexpression of both cassettes 1 and 2 appear gray. Scale bar, 70 μm. (E and F)Confetti configuration scores of free Plts (E) and Mks (F) imaged in situ (n = 5 mice).