Fig. 6. Cyr61 promotes CT domain- and heparan sulphate proteoglycan-dependent spreading of cells from blastulae; Xcyr61 is required for cell-cell adhesion. (A,B) Confocal microscope images of phalloidin-FITC stained activin-treated animal pole blastomeres spreading on fibronectin (A) or purified mouse Cyr61 (B). Cells plated on fibronectin have a polarised phenotype, with a least one long filopodium and, at the opposite end of the cell, lamellipodia. Cells plated on Cyr61 are characterised by extensive lamellipodia and no filopodia. (C-H) Phase-contrast images of live activin-treated animal pole blastomeres seeded on bovine serum albumin (BSA), fibronectin (FN), Cyr61 (CYR61) or Cyr61 lacking the CT domain (–CT) in the absence (C,D,E,G) or presence (F,H) of heparin (H). Cell spreading on Cyr61 requires the CT domain of that protein and is inhibited by heparin. Cell spreading on fibronectin is not inhibited by heparin. (I,J) Re-aggregation of blastomeres requires Xcyr61. Blastocoel roofs derived from control embryos or from embryos injected with MO2 (30 ng) were dissociated and allowed to re-aggregate. Cells derived from control embryos formed large clumps (I); those derived from MO2-injected embryos re-aggregated poorly (J). Scale bars: in B, 20 µm for A,B; in C, 100 µm for C-H; in I, 300 µm for I,J.