It has long been known that an individual’s sex has some influence on the likelihood of certain diseases. Thus, depression and anxiety tend to occur more in women, while men are more likely to experience certain neurodevelopmental disorders, such as attention deficit hyperactivity disorder or autism. They are also more sensitive to gestational stress and other conditions they may be exposed to before birth, such as maternal infections.
In fact, a study published in 2017 in the journal JAMA Psychiatry pointed out that for every four men with autism spectrum disorders (ASD), one woman is affected. On that occasion, the researchers from the Johann Wolfgang Goethe University who signed the work suggested that the thickness of the male cerebral cortex, thinner than theirs, could play a role in it.
It is not the first time that a neuroanatomical relationship has been sought to explain such a disparity in cases of ASD, but in an essay published in July 2018 collected by Nature Communications , a team of experts from the departments of Pharmacology at the University of Maryland and Biomedical Sciences of Pennsylvania indicates that the causes seem rather molecular, and that they should be sought in the placenta , an organ that can condition the future health of the baby in various ways.
A key gene and protein
In a study with rodents, these scientists observed that high levels of a protein in it, called H3K27me3, seem to increase the resilience of females towards the aforementioned gestational stress. Likewise, the OGT gene, which resides on the X chromosome – women have two and men one – provides some protection to female fetuses against some disturbances in the intrauterine environment.
“This connection could help us explain the considerable differences in neurodevelopment that occurs in humans of both sexes,” says Tracy L. Bale, one of the neuroscientists who has participated in this initiative. “In the placenta, the OGT gene and the H3K27me3 peptide are critical in encoding numerous proteins during pregnancy, which, over time, can have very different effects,” he adds.
In previous studies, Bale and his collaborators found that, at least in mice, the stress of the father can alter their sperm and, with it, affect the brain development of their offspring, who would be more likely to experience some neurodevelopmental disorders. The stressed parents also had offspring that offered a lower hormonal response to stress, a phenomenon that has been linked to the onset of some neuropsychiatric conditions, such as post-traumatic stress disorder.
Reference: Placental H3K27me3 establishes female resilience to prenatal insults. Tracy L. Bale et al. Nature communications. DOI: https://doi.org/10.1038/s41467-018-04992-1
