BIOCHEMICAL AND GENETIC ANALYSES OF AN EMBRYONIC ANTIGEN

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The goals of this proposal are to isolate and characterize a mammalian embryonic cell surface glycoprotein (ESGp) whose expression and biochemical structure appear to be developmentally regulated. ESGp from two cell through morula stage mouse embryos migrates as a single discrete electrophoretic band at a molecular weight of 90 kDa. At the blastocyst stage, however, the molecule migrates as a broad, heterogeneous band ranging from 90 to 110 kDa. Using teratocarcinoma cell analogues, I have shown that this band is actually a composite of three distinct molecules of MW 90, 95, and 110 kDa each of which is synthesized uniquely by the different cell types of the blastocyst: the embryonic ectoderm (EE) and visceral (VE) and parietal endoderms (PE), respectively. A survey of various mouse tissues and cell lines reveal only these three forms of glycoprotein. All undifferentiated cells and sperm express the 90 kDa "embryonic" form characteristic of embryonic ectoderm, which differentiated cells and adult tissues express the 110 kDa "adult" form characteristic of parietal endoderm; only embryonic visceral endoderm cells have been shown to express the 95 kDa form. In order to understand the significance of these molecular differences in mouse embryonic development, I propose to isolate the embryonic and adult ESGps and to analyze their protein and carbohydrate moieties. Antisera will be raised against the isolated glycoproteins and used to examine both the function and distribution of the ESGp in embryos, tissues and cell lines. The antibodies will also be used to screen cDNA libraries for ESGp positive clones. This cDNA will be sequenced and the ESGp sequences will be compared amongst themselves and with all other known sequences for possible homology. These studies will certainly enhance our current understanding of both the biochemical and genetic interactions regulating early mammalian development.