The study was conducted by researchers from the University of Exeter and King’s College. 400,000 genome areas have been analyzed in brain tissues of 179 embryos from 23 to 184 days (100 of them were males and 79 females). On the one hand, researchers have measured the methylation of these genome areas in the different stages of embryo development and, on the other, have compared the results of male and female embryos to see if there are significant differences between the two.
Methylation is a molecular mechanism of gene silencing: in a certain area of a gene, a group of methyl (a molecule) is added that does not express the gene. Methylation is the main epigenetic mechanism of regulation of genomic expression, fundamental in the processes that govern embryonic development.
“The prenatal stage is a time of enormous plasticity,” explains research director Jonathan Mill, “in which the structures that will control neurobiological function in the brain throughout life are defined. Knowing how genes are activated at this stage can help understand the origin of certain disorders related to neurodegeneration, such as autism and schizophrenia.” In fact, some of these alterations are more or less numerous among men or women, and therefore they have compared the results of male and female embryos (autism, for example, affects five times more men).
The results have been published by British researchers in the journal Genome Research. On the one hand, it is observed that the degree of methylation of approximately 28,700 sites varies depending on the development phase of the embryo and that the general tendency is to lose methylation as it progresses in its development. Researchers have commented that these methylation changes based on the development phase have been detected around several genes that play an important role in the development of neurogaration.
On the other hand, comparing the results of male and female embryos, methylation differences have been found in more than 8,000 locations. Apart from those on the X chromosome (since female embryos have two X chromosomes), the sum of the rest shows a 6.5% difference in the methylation pattern of male and female brain embryo tissues during the brain development process.
Although some of the areas methylated separately according to the sex of the embryo coincide with areas related to autism and schizophrenia, researchers cautiously warned that the research work is limited, as they have only had access to the tissues of the early stages of embryo development.