Thursday, May 11, 2006

Wait, does this mean genetics isn't everything?   posted by JP @ 5/11/2006 10:18:00 AM

This week's Nature has an excellent news article on epigenetics.

We all know humans share some large and horribly impressive percentage of our genome. But we're all different, and studies (using resources like the HapMap) of those under-appreciated percentages of the genome we don't all share should give us a clue to why that is.

But identical twins share an even more impressive percentage of their genome. How, given the fact that they're, well, identical, can they be different? The news article cites this study and describes it:
By studying 80 pairs of identical twins, ranging in age between 3 and 74, Esteller's team found that epigenetic differences were hardly detectable in the youngest twins, but increased markedly with age. These changes had a striking effect on gene activity: the number of genes that differ in activity between 50-year-old twins was more than three times that in pairs aged 3. "So we are more than our genes," says Esteller. "Not only is the DNA sequence important but also how gene activity is regulated in response to environment. This might explain why many identical twins have different susceptibility to disease."

And the promise for better understanding of phenotypes is there:
[Epigenetics] should also fill some big gaps in our grasp of how the environment affects a creature's constitution — epigenetic changes explain how simply altering the diet of a pregnant mouse, for example, can completely change the coat colour of her pups, or even alter their response to stress.

As of now, it's technically difficult to get a genome-wide view of methylation, but arrays to do just that should be just around the corner.

See also: Microarray-based DNA methylation profiling: technology and applications