Scientists have unlocked another piece of the nature versus nurture puzzle.
Researchers at the Salk Institute of Biological Studies released a report saying that the way mothers treat their children influences their kids’ DNA once they are adults.
The research, published in the journal Science, even provides evidence that mothering tactics can influence a person’s chances of developing schizophrenia.
The scientists said that a person’s DNA is influenced by the way they were parented as a child.
Researchers from the Salk Institute have found a new link between maternal care and mental health. They argue that the quality of maternal care that a person receives affects the number of copies of the L1 gene that they have. An artist’s impression is pictured
The new paper comes on the heels of a string of research claiming that childhood environments shape human brain development.
‘The work could provide insights into neuropsychiatric disorders such as depression and schizophrenia,’ the analysis said.
Professor Rusty Gage explained that the study changes our fundamental understanding of DNA.
He said: ‘We are taught that our DNA is something stable and unchanging which makes us who we are, but in reality it’s much more dynamic. It turns out there are genes in your cells that are capable of copying themselves and moving around, which means that, in some ways, your DNA does change.’
For at least ten years now scientists have understood that the majority of the cells in the brains of mammals undergo DNA changes.
A number of the changes occur because of ‘jumping’ genes – which are known officially as long interspersed nuclear elements (LINEs).
LINEs move around within the genome, and in 2005 Salk Institute researchers made a discovery about a LINE called L1.
L1 was previously known to ‘copy and paste itself’ in different places within the genome, but the researchers learned that it could get inside neuronal brain cells that were developing.
The study said: ‘The team had hypothesized that such changes create potentially helpful diversity among brain cells, fine-tuning function, but might also contribute to neuropsychiatric conditions.’
Pictured are the cells of a mouse’s hippocampus. These cells saw mobilization of the L1 gene (showing up green here). These genes – which are a part of a person’s DNA – are reportedly linked to how stressed one is as a child
Researcher Tracy Bedrosian explained: ‘While we’ve known for a while that cells can acquire changes to their DNA, it’s been speculated that maybe it’s not a random process. Maybe there are factors in the brain or in the environment that cause changes to happen more or less frequently.’
To answer this question, the scientists behind the new report observed naturally occurring variations among maternal care transferred from mice to their offspring.
Next they studied a part of the brain called the hippocampus in each of the offspring.
The hippocampus is thought to be involved in memory, some involuntary functions and emotion.
The study said: ‘The team discovered a correlation between maternal care and L1 copy number: mice with attentive mothers had fewer copies of the jumping gene L1, and those with neglectful mothers had more L1 copies and, thus, more genetic diversity in their brains.
‘To make sure the difference wasn’t a coincidence, the team conducted a number of control experiments, including checking the DNA of both parents of each litter to make sure the offspring didn’t just inherit their numbers of L1s from a parent as well as verifying that the extra DNA was actually genomic DNA and not stray genetic material from outside the cell nucleus.’
Additionally, the team cross-fostered offspring to make sure mice that were born to mothers who were neglectful were instead raised by attentive mothers and vice versa.
The initial results held, the study said, explaining: ‘Mice born to neglectful mothers but raised by attentive ones had fewer copies of L1 than mice born to attentive mothers but raised by neglectful ones.’
HOW DOES MATERNAL CARE SHAPE ADULT DNA?
A new report from the Salk Institute concludes that maternal care a person receives as a child shapes their DNA as an adult.
For the research scientists tested mice and looked specifically at their L1 genes.
They found that there is a link between neglectful mothers and a higher number of L1 copies within offspring.
Researchers discovered that the amount of copies of the L1 gene a person has could be linked to the maternal care they received as a child. Scientists used mice to test this theory
But they aren’t sure if there are consequences beyond this link.
The study said: ‘The researchers emphasized that at this point it’s unclear whether there are functional consequences of increased L1 elements.
‘Future work will examine whether the mice’s performance on cognitive tests, such as remembering which path in a maze leads to a treat, can be correlated with the number of L1 genes.’
The report said the researchers thought that offspring of neglectful mothers were more stressed.
Additionally, the researchers hypothesized that the stress caused genes to copy and more frequently move around.
The researchers concluded that L1 plays a unique role, and they noted that methylation could be the reason for the gene’s mobility.
Professor Gage said: ‘This finding agrees with studies of childhood neglect that also show altered patterns of DNA methylation for other genes.
‘That’s a hopeful thing because once you understand a mechanism you can begin to develop strategies for intervention.’