"It is now evident that the ability to optimally diagnose, prevent, and treat diseases will remain elusive
until it is more fully appreciated that human health and disease are not dependent solely upon genetic variations,
but rather upon complex interactions between alterations in the rigid genome and the plastic epigenome."
-- Randy Jirtle, PhD
until it is more fully appreciated that human health and disease are not dependent solely upon genetic variations,
but rather upon complex interactions between alterations in the rigid genome and the plastic epigenome."
-- Randy Jirtle, PhD
Epigenomic factors such as methylation and histone modification control the expression of underlying genes.
The Importance of Epigenetics
In the quote above, the pioneering epigenetics researcher Randy Jirtle describes the "rigid" genome and the "plastic" epigenome. What is this plastic epigenome and why does it matter to the understanding of the origins of disease and disorders?
Our genetic code, those 25,000 genes recently characterized as part of the Human Genome Project, provides the set of basic instructions for the creation of proteins that make all cells, tissues, and organs of an organism. These genes remain relatively stable over evolutionary time — humans and chimpanzees, for example, share 96% the same genetic code — and do not tend to mutate easily in response to environmental stressors.
On the other hand, the epigenome, which provides layers of complex molecular instruction to our genes, is particularly vulnerable to environmentally induced perturbations, particularly during critical windows of development.
Our genes can not and do not function without the epigenetic instruction book telling them when, where, and how to work. Our genome is essentially identical in all of our cell types—blood cells, brain cells, muscle cells, skin cells, etc. — but the epigenome programs each cell type to operate differently, to read different genes, to increase or downgrade or even silence gene expression.
Research has shown that epigenomic activity can be perturbed by various exposures, such as hormone-disrupting synthetic molecules, resulting in abnormalities in the expression of the underlying genes. Research has also shown that if germline epigenetics are altered, these alterations can be carried through to subsequent generations, resulting in a form of heritability that extends far beyond the confines of standard genomic pathogenesis that have long been the narrow focus of disease research.
In addition, studies have shown that mutagenesis of the core genome may be precipitated by environmentally induced destabilizing events in the epigenomic scaffold.
Our genetic code, those 25,000 genes recently characterized as part of the Human Genome Project, provides the set of basic instructions for the creation of proteins that make all cells, tissues, and organs of an organism. These genes remain relatively stable over evolutionary time — humans and chimpanzees, for example, share 96% the same genetic code — and do not tend to mutate easily in response to environmental stressors.
On the other hand, the epigenome, which provides layers of complex molecular instruction to our genes, is particularly vulnerable to environmentally induced perturbations, particularly during critical windows of development.
Our genes can not and do not function without the epigenetic instruction book telling them when, where, and how to work. Our genome is essentially identical in all of our cell types—blood cells, brain cells, muscle cells, skin cells, etc. — but the epigenome programs each cell type to operate differently, to read different genes, to increase or downgrade or even silence gene expression.
Research has shown that epigenomic activity can be perturbed by various exposures, such as hormone-disrupting synthetic molecules, resulting in abnormalities in the expression of the underlying genes. Research has also shown that if germline epigenetics are altered, these alterations can be carried through to subsequent generations, resulting in a form of heritability that extends far beyond the confines of standard genomic pathogenesis that have long been the narrow focus of disease research.
In addition, studies have shown that mutagenesis of the core genome may be precipitated by environmentally induced destabilizing events in the epigenomic scaffold.