Parental glucose phosphate isomerase activity in three-day mouse embryos.

Abstract

There has been suggestive evidence for embryonic genome activity in the preimplantation mouse embryo for several years. Whitten and Dagg (1961) found a paternal effect on cleavage rate before implantation, and Morris (1968) suggested that the X chromosome is necessary for early cleavage. However, to prove the presence of paternally derived gene activity, it is necessary to demonstrate the existence of a protein in the embryo coded for by a paternal allele. Chapman et al. (1971) have recently shown the presence on day 5 of development of the paternal variant of glucose phosphate isomerase (GPI) in mouse embryos derived by mating males and females containing the genes for different isozyme subunits. In addition, the work of Epstein (1972) on the total activity of hypoxanthine-guanine phosphoribosyl transferase suggests that the paternal allele for this enzyme, which is sex linked, is active at day 4 in development. Work in our laboratory during the past 2 years has also identified the paternal variant of GPI in the mouse embryo but at an earlier stage of development than previously reported. The studies reported here demonstrate paternal allele activity of GPI on the third day of development after only three cleavage divisions. This is not only earlier than previously reported for the mouse but is much earlier than found in fish, frog, and quail.