APLN alters EB morphology and increases expression of hematopoietic and endothelial genes during mesodermal differentiation. (A-C) Images of H&E-stained paraffin sections showing morphologic appearances of day 4 EBs differentiated in FGF2 alone or in BVS with and without APLN addition at day 2. Several neural rosettes (nr) are evident in the FGF2 EB. EBs that received BVS and APLN were larger with more prominent thin-walled cysts (cy). Scale bar: 100μM. (C) Histogram depicting the mean cell number per EB from day 3 to day 6 under each of these culture conditions. Error bars represent SEM for n = 6 independent experiments. *P < .01 comparing BVS+d2 APLN with BVS at each time point (see also supplemental Figure 5). (E) Histogram indicating the number of genes whose expression was up-regulated or down-regulated (≥ 2.5 fold change) at each time point in EBs cultured with BVS plus a single pulse of APLN at day 2 compared with those receiving BVS alone. (F-I) Histograms comparing the kinetics of gene expression in cells differentiated with or without APLN for selected genes. Panels are grouped to show the profiles of genes whose expression was maximal from day 3 to day 6 as indicated (see also supplemental Figure 6). Abbreviations for gene names are expanded in supplemental Table 8.