Brain complexity: parental contribution to personality (Introduction)

by David Turell , Thursday, March 22, 2018, 18:36 (2438 days ago) @ David Turell

A new study in mice demonstrates how nurture by different moms affects the brain:

https://medicalxpress.com/news/2018-03-early-life-dna-adult-brain.html

"In the perennial question of nature versus nurture, a new study suggests an intriguing connection between the two. Salk Institute scientists report in the journal Science that the type of mothering a female mouse provides her pups actually changes their DNA. The work lends support to studies about how childhood environments affect brain development in humans and could provide insights into neuropsychiatric disorders such as depression and schizophrenia.

"'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," says Rusty Gage, a professor in Salk's Laboratory of Genetics. "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 a decade, scientists have known that most cells in the mammalian brain undergo changes to their DNA that make each neuron, for example, slightly different from its neighbor. Some of these changes are caused by "jumping" genes—officially known as long interspersed nuclear elements (LINEs)—that move from one spot in the genome to another. In 2005, the Gage lab discovered that a jumping gene called L1, which was already known to copy and paste itself into new places in the genome, could jump in developing neuronal brain cells.

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" Gage, Bedrosian and colleagues began by observing natural variations in maternal care between mice and their offspring. They then looked at DNA from the offspring's hippocampus, which is involved in emotion, memory and some involuntary functions. 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.

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"The researchers hypothesized that offspring whose mothers were neglectful were more stressed and that somehow this was causing genes to copy and move around more frequently. Interestingly, there was no similar correlation between maternal care and the numbers of other known jumping genes, which suggested a unique role for L1. So, next, the team looked at methylation—the pattern of chemical marks on DNA that signals whether genes should or should not be copied and that can be influenced by environmental factors. In this case, methylation of the other known jumping genes was consistent for all offspring. But it was a different story with L1: mice with neglectful mothers had noticeably fewer methylated L1 genes than those with attentive mothers, suggesting that methylation is the mechanism responsible for the mobility of the L1 gene.

"'This finding agrees with studies of childhood neglect that also show altered patterns of DNA methylation for other genes," says Gage, who holds the Vi and John Adler Chair for Research on Age-Related Neurodegenerative Diseases. "That's a hopeful thing, because once you understand a mechanism, you can begin to develop strategies for intervention"

"The researchers emphasize 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. "

Comment: this work confirms what we have thought. It also reemphasizes that neuronal genetics helps form the personality in the way that brain neurons are constructed to receive the work of the s/s/c in development.