Maternal Microdeletion at the ICR in Mice Increases Offspring Susceptibility to Environmental Perturbation.

Deficiency of methyl donor nutrients folate, choline, and methionine (methyl deficiency) during gestation can impair fetal development and perturb DNA methylation. Here, we assessed genetic susceptibility to methyl deficiency by comparing effects in wildtype C57BL/6J (B6) mice to mutant mice carrying a 1.3 kb deletion at the Imprinting Control Region (ICR) ( ). The mutation mimics microdeletions observed in Beckwith-Wiedemann syndrome (BWS) patients, who exhibit epimutations in that cause loss of imprinting and fetal overgrowth. Dams were treated during pregnancy with 1 of 4 methyl sufficient (MS) or methyl deficient (MD) diets, with or without the antibiotic commonly used to deplete folate producing gut microbes. As expected, after ~9 weeks of treatment, dams in MD and MD + antibiotic groups exhibited substantially reduced plasma folate concentrations. mutant lines were more susceptible to adverse pregnancy outcomes caused by methyl deficiency (reduced birth rate and increased pup lethality) and antibiotic (decreased litter size and litter survival). Surprisingly, pup growth/development was only minimally affected by methyl deficiency, while antibiotic treatment caused inverse effects on B6 and lines. B6 pups treated with antibiotic exhibited increased neonatal and weanling bodyweight, while both wildtype and mutant pups of heterozygous dams exhibited decreased neonatal bodyweight that persisted into adulthood. Interestingly, only antibiotic-treated pups carrying the mutation exhibited altered DNA methylation at the ICR, suggesting ICR epimutation was not sufficient to explain the altered phenotypes. These findings demonstrate that genetic mutation of the ICR increases offspring susceptibility to developmental perturbation in the methyl deficiency model, maternal and pup genotype play an essential role, and antibiotic treatment in the model also plays a key independent role.