25 June 2008

Nature and Nurture Linked by Epigenetics

You cannot separate a person's genes from his environment. The two are irrevocably linked by several mechanisms. One of the most important ways in which the environment affects gene expression is via an epigenetic mechanism called "methylation." DNA methylation is always at work in the animal, initially helping guide differentiation and development of tissues and organs, and responding to the environment and shaping gene expression by putting parts of the DNA "off limits" to the gene expression system, or in de-methylation putting parts of the DNA back "on-line".
Johns Hopkins researchers who studied the genomes of people in Iceland and Utah say they may have found a clue to why people are increasingly prone to disease as they age...a person could become more prone to heart disease, cancer and other diseases of aging because certain genes that used to function no longer do so - or vice versa. Animal studies have shown that such changes can be triggered by environmental forces such as diet...Collaborating with scientists at the University of Iceland, the Hopkins researchers studied two populations over time to see if they could observe changes in the amount of "methylation" present in a person's genome.

...The degree of methylation is part of a person's epigenetics - aspects of an individual's makeup that exist apart from the genes themselves...The researchers tapped into continuing studies in Utah and Iceland, both havens for genetic research because of homogeneous populations. The researchers obtained DNA samples given over a decade apart by 111 people in Iceland and 126 in Utah.

For each person, they measured the amount of methylation present at each point in time - about a third of the subjects in Iceland and 30 percent in Utah had substantial changes over the period.

...Environmental factors can increase the amount and the location of methylation along the genome, influencing whether genes are functioning or not. The changes can also occur randomly, as cells divide and information gets lost or jumbled. __Source_via_Kurzweilai.net
Being able to investigate the state of methylation and other epigenetic states and processes, takes understanding of gene expression light-years beyond the mere genome. Methylation is one means by which a once-pristine genome is "marked by life." As scientists better learn to read the language of epigenetic markers, they will be able to better understand the history and current state of particular organisms (and people).

Of course, being able to modify epigenetic states will be a therapeutic tool even more potent--initially--than gene insertion. The reason for this is that the existing genes already know how to work together. When you pop a new gene into the sequence, you are never quite sure ahead of time how it will work.

More here.

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