Expression of Jagged 1 protein in cultured mouse stromal cells. (A and B) Cultured primary mouse stromal cells were allowed to adhere to slides coated with type I collagen and then stained immunohistochemically with a rat anti–Jagged 1 polyclonal antiserum (A) or with control anti-rat Ig (B). Antibody binding was visualized by staining with diaminobenzidine, and the cells were counterstained with hematoxylin. (C) Western blot of cultured primary mouse stromal cell extract, which was separated on a 3% to 12% gradient SDS-polyacrylamide gel electrophoresis under reducing conditions, transferred, and probed with a goat anti-Jagged 1 antibody. The lefthand column shows the position of molecular weight markers (Amersham); the figures are molecular weights in kilodaltons. The single band detected at approximately 170 to 180 kD corresponds to Jagged 1.