In this experiment the scientists tried to examine how maternal diet during the periconceptional period affects the DNA methylation at metastable epialleles (MEs) in the offspring, an if there are any permanent phenotypic consequences. Gambian women living in rural areas experience seasonal differences in the diet that occurs naturally, whch allowed them to conduct such experiment. To test their initial hypothesis about the connection between periconceptional nutrition of mothers and developmental establishment of DNA methylation at candidate MEs in the offspring, the scientists compared DNA methylation in peripheral blood leukocytes (PBL) obtained from Gambian children who were conceived during either the dry or the rainy season. The results of this experiment indicated that DNA methylation at MEs was higher in those individuals who were conceived during the nutritionally challenged rainy season. It provided the scientists with the evidence of a permanent, systemic effect of periconceptional environment on human epigenotype.The second part of the experiment was aimed at confirming concordance among tissues derived from all 3 germ layers, and establishing whether or not interindividual epigenetic variation at candidate MEs is conserved in genetically divergent populations. In order to do so, the scientists tested post-mortem hepatic, kidney and brain tissuesthat they obtained from 8 healthy Vietnamese donors deceased in car accident.
Autopsy samples of all three tissues listed above indicated that highly correlated across tissues DNA methylation that was represented in three embryonic germ layer lineages. Because monozygotic twin pairs had substantial discordance in DNA methylation at these loci, it was concluded that their epigenetic state is established stochastically.