Fig. 4.
ECM signaling regulates definitive endoderm induction and contractility. (A) Mouse ESCs (CCE and R1) were grown in definitive endoderm (DE) or pluripotency (PP) induction medium on decellularized fibroblast-derived matrices supplemented with FRET fibronectin and either 0 μg/ml (– exogenous laminin) or 50 μg/ml (+ exogenous laminin) mouse laminin-111. Equal amounts of DOC-insoluble ECM were blotted for laminin or fibronectin after 1 and 5 days of ESC culture. (B) R1 ESC mean±s.e.m. (n>300) nuclear SOX17 staining intensity and (C) average extracellular matrix FRET intensity ratios (the box represents the 25–75th percentiles, and the median is indicated; the whiskers show the 10–90th percentiles, n>10) were measured after 5 days of definitive endoderm induction in the presence or absence of the α5β1-integrin function-blocking antibody BIIG2. *P<0.05. a.u., arbitrary units.