DEVELOPMENTAL BIOLOGY 77,480-487 (1980) BRIEF NOTES Identification of Noncollagenous Basement Membrane Glycopolypeptides Synthesized by Mouse Parietal Entoderm and an Entodermal Cell Line CHIN C. HOWE AND DAVOR SOLTER The Wistar Institute of Anatomy and Biology, 36th Street at Spruce, Philadelphia, Pennsylvania 19104 Received June 15, 1979; accepted in revised form December 18, 1979 Using two-dimensional gel electrophoresis, we have identified two noncollagenous basement membrane (BM) glycopolypeptides which are synthesized by the mouse teratocarcinoma-derived parietal yolk sac (PYS) cell line. These glycopolypeptides have molecular weights of about 200,900 and isoelectric points of about 5.6. Polypeptides with identical parameters are synthesized by the parietal entodermal cells of mouse embryos and are found in Reichert’s membrane. Pluripotent embryonal carcinoma cells (ECC) synthesize considerable amounts of the two polypeptides, whereas the yield from nullipotent ECC is negligible. The treatment of nullipotent F9 cells with retinoic acid, which induces entodermal differentiation, activates the synthesis of these polypep- tides. These results indicate that the two pol.vpeptides can be used as markers of parietal entoderm differentiation. -_ INTRODUCTION It has been demonstrated in previous studies by different techniques that the mouse parietal yolk sac (PYS) embryonic cells and PYS carcinoma cells produce a particular kind of basement membrane (BM) (Jetten et al., 1979; Martinez-Her- nandez et al., 1974; Pierce et al., 1962). Parietal entoderm is probably the first dif- ferentiated cell type observed during in vi- tro differentiation of mouse blastocysts and inner cell masses (ICM) (Hogan and Tilly, 1978; Wiley et al., 1978; Solter and Knowles, 1975; Solter et al., 1974). It is also the first observed during in vitro differentiation of embryonal carcinoma cells (ECC) (Martin and Evans, 1975; Martin et al., 1977; Strick- land and Mahdavi, 1978). A biochemical marker for parietal entoderm would be very useful in analysis of this event. In one of our recent studies, we examined the in vitro differentiation of murine ECC and ICM to embryoid bodies (EB). Using two-dimensional gel electrophoresis of [35S]methionine-labeled proteins, we de- tected two high molecular weight acidic polypeptides in ICM-EB and ECC-EB. These polypeptides were also found in ter- atocarcinoma-derived PYS entodermal cells but not in teratocarcinoma-derived fi- broblasts (Howe et al., 1980). It was there- fore of interest to see whether these poly- peptides were components of the BM. It is generally recognized that the BM consists of collagenous and one or more noncollagenous glycoprotein components (Kefalides, 1971; Kefalides and Denduchis, 1969; Lee et al., 1969). The amino acid composition and molecular weight of one noncollagenous glycoprotein have been de- termined (Chung et al., 1979; Johnson and Starcher, 1972), but its isoelectric point is as yet unknown. The high molecular weight acidic polypeptides, which we identified as noncollagenous glycoprotein components of the BM, are synthesized by teratocarci- noma-derived PYS cells and by PYS em- bryonic cells, and are present in Reichert’s 480 0012.1606/80/080480-08$02.60/O Copyright 0 1980by Academic Press, Inc. All rights of reproduction in any form reserved.