The developmental potential of embryos and cells that are deficient in glycolysis

• Main Author: Kelly, Annemarie
• Published: University of Edinburgh 1996
• Subjects: 611
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.653261

Previous work showed that mouse embryos homozygous for a null allele of the gene that encodes the glycolytic enzyme, glucose phosphate isomerase (GPI), died shortly after implantation. Although the homozygous GPI null embryos cannot produce their own GPI, because they lack the appropriate gene, they survived until 7.5 - 8.5 days (West <I>el al</I>, 1990) and some extraembryonic tissues survived until 10.5 days. A histological study was undertaken to determine when the first signs of abnormality become apparent in the dying homozygous GPI null embryos. The critical time period for these mutant embryos was found to be between 6.5 days and 7.5 days. This is after the oocyte coded GPI is exhausted so the embryo has to rely on it's own production of the enzyme. At this stage the embryo is implanting under relatively anaerobic conditions because the placenta has not yet formed. The mutant embryos fail to gastrulate properly and produce only a small amount of mesoderm. The abnormally developed egg cylinder expands to form an empty sac-like structure. The membrane that resembles the yolk sac is in fact comprised of extraembryonic ectoderm and extraembryonic endoderm. Aggregation chimeras were produced between homozygous GPI null embryos and normal embryos to examine whether homozygous GPI null cells could survive for longer when combined with normal cells. Because the homozygous GPI null embryos are embryo lethal, two heterozygotes were intercrossed to produce embryos, 25% of which should be homozygous for the null allele. All of the embryos produced from the intercrossing of the heterozygotes were aggregated to normal 8 - cell embryos.