Genetic differences in glucose phosphate isomerase activity among mouse embryos.
We have compared mouse embryos of three heterozygous, congenic genotypes (with high, medium and low levels of oocyte-coded glucose phosphate isomerase (GPI-1) activity respectively) to test whether 1) the survival time of oocyte-coded GPI-1 activity in the early embryo is affected by its activity level in the oocyte and 2) whether embryo-coded GPI-1 is detected earlier in embryos that inherit low levels of oocyte-coded GPI-1. The oocyte-coded GPI-1 was entirely GPI-1A allozyme in the high and medium groups but was the less stable GPI-1C allozyme in the low group. We determined total GPI-1 activity and the ratio of different GPI-1 allozymes in early embryos and calculated the activity of oocyte-coded and embryo-coded GPI-1. In all three groups, the oocyte-coded enzyme activity remained at a more or less constant level for the first 21 1/2 days. Some oocyte-coded GPI-1 remained in 4 1/2 day embryos from the high and medium groups but was gone by 5 1/2 days. Very little remained in 4 1/2 day embryos that inherited low levels of a less stable form of the enzyme (GPI-1C allozyme). Despite a 4- to 5-fold difference in initial oocyte-coded GPI-1 activity, no differences were seen among the three genotypically distinct groups of embryos in the time of activation of the embryonic Gpi-1s genes. The embryo-coded GPI-1 was first detectable in 3 1/2 day compacted morulae in all three groups. The level of oocyte-coded GPI-1, in the high group, when embryo-coded GPI-1 was first detected was higher than the level in the low group at any stage prior to detection of embryo-coded GPI-1.(ABSTRACT TRUNCATED AT 250 WORDS)
West
J D
JD
Department of Obstetrics and Gynaecology, University of Edinburgh, UK.
Flockhart
J H
JH
D000818:Animals; D001755:Blastocyst / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D004622:Embryo, Mammalian / Q000201:enzymology*; D005260:Female; D005956:Glucose-6-Phosphate Isomerase / Q000235:genetics* / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009865:Oocytes / Q000201:enzymology*; D011247:Pregnancy
D007527:Isoenzymes; D005956:Glucose-6-Phosphate Isomerase