Fig. 1. Spontaneous or BMP-2-induced extra-embryonic differentiation of human ES cells. (A,B) Phase contrast morphology of control (A) or BMP-2 (B, 25 ng/ml) cells 7 days after treatment. A shows typical stem cell morphology. (C) Spontaneously differentiating ES cell colony. (D) Hematoxylin and eosin stained section of cells similar to those shown in C after removal from culture dish. (E,F) Phase contrast (E) and indirect immunofluorescence (F) image of BMP-2-treated cells stained with antibody to cytokeratins 8, 18 and 19. (G,H) Phase contrast (G) or indirect immunofluorescence (H) micrographs of BMP-2-treated cells stained with antibody to laminin. (I) Double-label staining of BMP-2-treated cells stained with GCTM-2 recognizing a stem cell surface proteoglycan (red) and SPARC (green). (J,K) Phase contrast (J) or indirect immunofluorescence (K) micrographs of a cystic structure and cells at its base stained with antiserum to alphafetoprotein. Wall of cyst (at left) and cells at base (at right) are stained. Bars, A-C, 50 µM; D, 10 µM; E-K, 20 µM.