Expression of the Tcp-1 locus of the mouse during early embryogenesis.

The synthesis of proteins by preimplantation mouse embryos was studied by two-dimensional (2D) gel electrophoresis of proteins labelled with [35S]methionine. The product of the Tcp-1 locus of the mouse, p63/6.9, is synthesized by morula and blastocyst stage embryos, but is not detectable in 2-cell embryos. These results indicate that maternal expression (oocyte-specific) of this gene is not occurring and that this gene may be developmentally regulated. Blastocysts which are allowed to implant in vitro have rates of protein synthesis that permit fluorographs of single embryos to be performed. These embryos can be unambiguously identified for their t-complex genotype. Quantitation of the amounts of the Tcp-1a and Tcp-1b allelic products in morula embryos suggested delayed expression of the paternal allele.