Effects of maternal and embryonic genotype on prenatal survival in two selected mouse lines

The effect of fetal and maternal genotype on embryo survival was studied in two lines of mice from the same base population: line E, selected for high embryo survival, and line CN-, selected for small litter size. Embryos were collected at 3.5 days postcoitus from normally mated donors of both lines and were transferred to the uteri of 2.5-day pseudopregnant recipients from each line. The number of embryos recovered and the proportion of those recovered that had been fertilized were greater in line E donors than in line CN- donors (P < .05). Development into blastocysts was slower for CN- embryos. The proportion of recipient females that were pregnant was higher for line E than for line CN- after transfer of line E embryos (P < .005). The same trend was observed following transfer of line CN- embryos (P < .10). Embryos of both lines showed greater survival when transferred to line E recipients than when transferred to line CN- recipients (P < .005), and, within line E recipients, E embryos tended to survive better than did CN- embryos (P < .10). The results suggest that although the genotype of the embryo may play a role, the maternal genotype has greater influence on embryo survival in the two lines of mice.