Washington: New maps of chemical modifications to brain DNA have revealed that massive epigenetic changes takes place during a child`s first few years of life.
During development in mammals, chemical tags called methyl groups are added to certain cytosine nucleotides in the DNA, which affects how nearby genes are expressed.
Later, environmental stressors such as stress, diet and disease can alter these patterns and change the genes` expression.
These epigenetic modifications appear to play a role in some neurological disorders.
Because epigenetic patterns can differ between tissues in the body, Ryan Lister of the University of Western Australia in Crawley and colleagues decided to zero in on the brain`s methylation.
The team collected nine human brains including examples from foetuses, two-month-old babies, toddlers, teenagers and older adults, and the same from mice at equivalent stages of development.
The researchers removed the frontal cortex, which is involved in thought processing, and separated out the neurons from other cells in the cortex.
By treating the neurons` DNA with a chemical that highlights methylated cytosines, and then sequencing the genomes, the researchers created a map showing how the pattern of methylation changes as the brain develops.
During the first two years of life, they found, a massive wave of methylation sweeps through the brain, altering the DNA in numerous genes involved in forming connections between neurons.
Lister said that this period of reprogramming and rewiring might leave the brain`s DNA particularly susceptible to damage by environmental factors that could disrupt correct methylation.