Parietal endoderm cell line from a rat blastocyst

We have derived a cell line, RE1, from a pre-implantation rat blastocyst, r esembling morphologically; the L2 cell line from a parietal yolk sac carcin oma of the rat, as well as parietal endoderm cell lines of the mouse. The s ub-cellular organization and epithelial characteristics of RE1 cells are de scribed. The cells express cytokeratins of simple epithelia, and vimentin; and demonstrate synthesis of proteins of the extracellular matrix, such as laminin and collagen IV. Extensive Reichert's-like basement membrane is for med by RE1 cells when grown in suspension as aggregates. Cells have a micro villous surface morphology and abundant, rough endoplasmic reticulum which is swollen with apparent, secretory material. These morphological and cytoc hemical features are characteristic of parietal endoderm cells in vivo, and the RE1. cell line is deduced to be rat parietal endoderm. In addition, RE 1 cells were examined for expression of stage-specific embryonic antigens: cells reacted with antibody against SSEA-1/TEC-1 and EMA-1, constituting th e first observation of parietal endoderm cells expressing the respective ep itopes. RE1-cell monolayers did not generate transepithelial resistances or potential differences in vitro, consistent with their formation of leaky e pithelia. Our observations on RE1-cell morphology and ultrastructure are co nsistent with the occurrence of epithelial-mesenchyme transitions in cultur e. (C) 2001 Harcourt Publishers Ltd.