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CHARACTERIZATION OF AN ANTIGEN PRESENT ON TESTICULAR CELLS AND PRE‐IMPLANTATION EMBRYOS WHOSE EXPRESSION IS MODIFIED BY THE t12 HAPLOTYPE

In attempts to identify cell surface molecules specified by lethal genes in the T/t‐complex, we prepared a rabbit antiserum that has cytotoxic activity against testicular cells from males heterozygous for t12, but not against wild type cells. However, anti‐t12 serum immunoprecipitates the same major component, a glycoprotein of mol. wt. 87,000 daltons, from galactose‐labelled C3H.+/t12 testicular cell lysate and from congenic C3H.+/+ lysate, although the gp87 molecule precipitated from +/t12 cells appears to be more highly galactosylated than the +/+ form. The antigen is heavily glycosylated in both genotypes, since when testicular cells are treated with tunicamycin before immunoprecipitation, a protein of 40,000‐42,000 daltons is obtained.Gp87 is also present on pre‐implantation embryos, and on teratocarcinoma cells, but is barely detectable on any adult somatic cells examined. Its expression is developmentally regulated during pre‐implantation stages, but the temporal pattern of its expression appears to be different between wild type and t12 embryos. Thus, we believe we have identified a molecule that may play a role in the differentiation of testicular cells and pre‐implantation embryos, and that is either specified by genes in the t12 haplotype, or responsive in some way to the effects of t12.