A new study has begun to establish a link between placental DNA and the risk of mental disorders later in life. However, more research is needed to better understand these findings. (Image credit: Katja Knupper/Die Fotowerft/DeFodi Images via Getty Images)
Scientists have identified a potential link between the placenta, the organ that provides the developing fetus with oxygen and nutrients, and the development of mental illness.
If confirmed, the discovery could help experts better understand how some mental disorders may begin to develop before birth, and how their likelihood may be increased by events that occur in the womb.
According to the “neurodevelopmental hypothesis,” first proposed in 1987 by neuroscientist Daniel Weinberger, schizophrenia is shaped by fetal brain development. The theory suggests that a combination of genetic risk factors and conditions during pregnancy shape early brain wiring, which in turn increases the likelihood of developing schizophrenia and other mental disorders later in life.
Although this hypothesis is widely accepted as plausible, the exact mechanism behind it remains unclear.
Now, a new study published March 14 in the journal Nature Communications shows that part of the answer may lie in epigenetic modifications of the placenta. These chemical changes to DNA molecules don’t affect the genes themselves, but rather influence which ones are turned on or off.
In the study, the scientists analyzed DNA from 368 placenta samples, focusing on epigenetic changes known as DNA methylation, which affect gene expression. They found more than 214,000 DNA sites in the placenta where DNA methylation occurs frequently.
Many of these methylated DNA sites were in areas where DNA is actively used to make RNA and proteins; RNA is the genetic equivalent of DNA that helps carry instructions for assembling proteins in the cell. So it’s possible that DNA methylation can either silence or activate genes that play a role in the development and function of the placenta, the team said. Changes in placental function are important because the placenta serves as a link between the maternal environment and the fetus.
Previous studies have linked certain genes to mental disorders, including schizophrenia, bipolar disorder and major depressive disorder. So the team compared their placental DNA methylation data to existing data on these disorders to see if the same genes were involved.
They found that several genes linked to mental disorders were highly methylated in the placenta. This led them to speculate that methylation might affect the activity of these placental genes — changing whether they make proteins or not — which in turn could influence fetal brain development.
To investigate potential effects on the developing fetal brain, the scientists looked at how DNA methylation alters gene expression in the placenta. They found that many of the genes affected by DNA methylation are involved in immune responses. Based on these results, they hypothesized that DNA methylation in the placenta affects the expression of genes related to immunity, which in some cases may increase the risk of infections.
Previous studies have linked infections during pregnancy — including seasonal flu and Zika — to altered neurological development in the fetus and an increased risk of mental disorders in offspring. Scientists believe that infections during pregnancy may affect fetal brain development by triggering immune responses in the mother that can then lead to inflammation in the fetal brain; or the microbes may directly infect fetal brain cells.
A new study suggests a possible link between placental epigenetics and these harmful immune responses. However, “a major problem is that this work does not provide direct experimental evidence that specific methylation patterns lead
Sourse: www.livescience.com
