SLC2A2 and Hyperglycemia: Absence of Slc2a2/Glut2 expression in visceral yolk sac of knockout mutant embryos may reduce glucose transport to the mutant embryo and thus “normalize” the nutritional environment for mutants, but this would not apply for the yolk sacs associated with heterozygous or wildtype embryos, which would continue to be susceptible to the detrimental effects of maternal hyperglycemia.