Researchers at the National Institute of Health said a regulatory mechanism that turns genes on and off in the brain's executive hub are among the most environmentally responsive.
The mechanism, called DNA methylation -- a biochemical process that is important for normal development in higher organisms -- abruptly switches from off to on within the human brain's prefrontal cortex during this pivotal transition from fetal to post-natal life. As methylation increases, gene expression slows down after birth.
This mechanism leaves chemical instructions that tell genes what proteins to make -- what kind of tissue to produce or what functions to activate.
Although not part of DNA, these instructions are inherited from a child's parents, but they are also influenced by environmental factors, allowing for change throughout the lifespan, the study said.
"Developmental brain disorders may be traceable to altered methylation of genes early in life," lead author Barbara Lipska, a scientist in the NIH's National Institute of Mental Health said in a statement. "For example, genes that code for the enzymes that carry out methylation have been implicated in schizophrenia. In the prenatal brain, these genes help to shape developing circuitry for learning, memory and other executive functions which become disturbed in the disorders."
The study, published in the American Journal of Human Genetics, found methylation in a family of these genes changes dramatically during the transition from fetal to post-natal life and that this process is influenced by methylation itself, as well as genetic variability.
"Regulation of these genes may be particularly sensitive to environmental influences during this critical early life period," Lipska said.