Early experiences in childhood can alter gene expression – Harvard study

http://developingchild.harvard.edu/index.php/library/reports_and_working_papers/working_papers/wp10/

The approximately 23,000 genes that children inherit from their parents form what is called the “structural genome.” Scientists liken the structural genome to the hardware of a computer— both determine the boundaries of what’s possible, but neither works without an operating sys- tem to tell it what to do. In the genome, that operating system is called the epigenome.4 Like the software in an operating system, the epigenome determines which functions the genetic “hard- ware” does and does not perform.5  This system is built over time as positive experiences, such as exposure to rich learning opportunities, or negative influences, such as environmental toxins or stressful life circumstances, leave a chemical “signature” on the genes. These signatures can be temporary or permanent, and both types affect how easily the genes are switched on or off.   For example, even though identical twins have the same structural genomes, their different experiences result in different epigenomes.6 

These differing experiences leave signatures on the epigenome that cause some genes to be expressed differently.  This explains why genetically identical twins, though similar in many ways, can exhibit different behaviors, skills, health, and achievement in both school and, later, in the workplace.  The field of epigenetics is relatively new and at the cutting-edge of the biological sciences. To date, scientists have found that temporary epigenetic chemical modifications control when and where most of our genes are turned on and off. This, however, is not the en- tire story. Certain experiences can also cause enduring epigenetic modifications in hundreds of genes that have already been identified, and the list is growing.7,8 Increasing evidence shows that experience-driven, chemical modifications of these latter genes appear to play particularly key roles in brain and behavioral development. This new knowledge has motivated scientists to look more closely at the factors that shape the epigenome and to study whether interventions can reverse these modifications when negative changes occur.
 Nutritional status, exposure to toxins and drugs, and the experiences of interacting with varied environments can all modify an individual’s epigenome.9 Epigenetic instructions that change how and when certain genes are turned on or off can cause temporary or  enduring health problems. Moreover, research in both animals and humans shows that some epigenetic changes that occur in the fetus during pregnancy can be passed on to later generations, affecting the health and welfare of children, grandchildren, and their descendents.10,11,12 
For example, turning on genes that increase cell growth, while at the same time switching off genes that suppress cell growth, has been shown to cause cancer.13,14 Repetitive, highly stressful experiences can cause epigenetic changes that damage the systems that manage one’s response to adversity later in life.2,3,15
On the other hand, supportive environments and rich learning experiences generate positive epigenetic new scientific research shows that environmental influences can actually affect whether and how genes are expressed. Thus, the old ideas that genes are “set in stone” or that they alone determine development have been disproven. In fact, scientists have discovered that early experiences can determine how genes are turned on and off and even whether some are expressed at all.1,2,3
Therefore, the experiences children have early in life—and the environments in which they have them—shape their developing brain architecture and strongly affect whether they grow up to be healthy, productive members of society. This growing scientific evidence supports the need for society to re-examine the way it thinks about the circumstances and experiences to which young children are exposed. 
Like the software in a computer’s operating system, the epigenome determines which functions the  genetic “hardware” does and does not perform.

  PART 2 next …