APLN binds posterior mesodermal and anterior mesendodermal progenitors in differentiating hESCs. (A) Amino acid sequence of synthesized APLN-13 N-terminal pyroglutamate (N-Pyr) peptide conjugated to fluorescein (Fl). (B) Staining protocol used to label cells with APLN-13–Fl. (C-F) Flow cytometric analysis of undifferentiated (d0) hESCs and day 3 EBs differentiated under neurectodermal (FGF), posterior mesodermal (BVS), and anterior mesendodermal (B^loVSA^hi) conditions labeled with APLN-13–Fl and Abs to PDGFRα or EPCAM. The growth factor concentrations are provided in “Cell culture and differentiation” and supplemental Figure 1. The percentage of cells falling into each quadrant is indicated in top right of each plot.