CARBOHYDRATE ANTIGEN EXPRESSION IN MURINE EMBRYONIC STEM-CELLS AND EMBRYOS .2. SIALYLATED ANTIGENS AND GLYCOLIPID ANALYSIS

A mouse embryonic stem (ES) cell line E14 and early mouse embryos were stained with a panel of 15 monoclonal antibodies recognizing sialylat ed or potentially sialylated carbohydrate determinants. Sialyl Le-x an d sialyl Le-a were detected on the pre-implantation embryo from the 8- cell stage, and sialyl Le-a weakly on undifferentiated ES cells. Chang es in cell surface carbohydrates occurred after induction of ES cell d ifferentiation with retinoic acid (RA) and dibutyryl cAMP. Qualitative analysis of the neutral glycolipids of untreated and RA-treated ES ce lls using high-performance thin-layer chromatography (HPTLC) revealed few differences between the two types of culture. The major gangliosid es in both cultures were indicative of an active 'a' ganglioside synth esis pathway. GD3, a precursor of the 'b' synthesis pathway, previousl y reported to be characteristic of embryonal carcinoma (EC) cells, was absent. RA-induced differentiation caused a shift in the spectrum to more complex gangliosides. Application of fast atom bombardment mass s pectrometry (FAB-MS) to permethylated derivatives of individual bands permitted partial characterization of an unusual sialylated glycolipid and a rare ganglioside with the suggested structure of GalNAc-GD1a.