A new study conducted by researchers from the University of the Basque Country in Spain sought to understand how a pregnant mother’s Body Mass Index (BMI) during the beginning of pregnancy impacts the molecular profiles of the placenta.
“And more specifically, placental DNA methylation– or the addition of a group compromising one carbon and three hydrogens in a specific position in the DNA molecule,” explained Nora Fernández-Jiménez, a Faculty of Medicine and Nursing lecturer.
To date, this was the largest study focusing on placental DNA methylation. It included 2,631 mother and child pairs from North America, Europe, and Australia.
Unlike more familiar mutations– which involve the substitution of one nucleotide in the DNA sequence for another– methylation is a DNA modification that regulates gene expression without actually altering the DNA sequence.
Recent research has found that methylation bridges the gap between the fetal genome and the intrauterine environment. In other words, the rate of methylation in a genome region may increase due to the environment.
But this kind of increase usually causes DNA to become more compact– meaning that these regions cannot be accessed for transcription. This ultimately leads to some genes being silenced.
On the flip side, the opposite effect could also occur. For instance, the rate of methylation in a genome region could decrease in response to the environment.
“In this case, the DNA obtains an open configuration to which the transcription machinery has better accessibility, and gene expression would be increased as a result,” said Fernández-Jiménez.
“In both cases, the sequence remains intact, but the genome behaves in one way or another.”