Tuesday, May 30, 2006

Vive Lamarck!   posted by JP @ 5/30/2006 05:02:00 AM

A little while back, I mentioned epigenetics, noting that arrays for the detection of methylated sites in the genome are starting to become available. Recently released from The American Journal of Human Genetics is a new article that uses just that type of array to detect epigenetic variation in human sperm. what do they find? Here's the first paragraph of the discussion:
In this study, we performed an in-depth analysis to address the question of epigenetic variability in the germline. The main conclusions are that (1) the male germline exhibits locus-, cell-, and age-dependent DNA methylation differences and that (2) DNA methylation variation is significant across unrelated individuals, at a level that, by far, exceeds DNA sequence variation.

That is, different people carry different epigenetic information in their germline. The next question is clear-- does this information get tranmitted to the next generation?

In general, I had been under the impression that methylation was "cleaned" off the DNA after fertilization, but that's nothing but a general rule, and exceptions abound. If epigenetic information can be efficiently transmitted from parents to their children, that would be a huge--for the study of disease, for the study of genetic conflict, and for genetics in general. The authors of the article mention that the age of your father is a risk factor for schizophenia, and transgenerational effects on other traits have been seen before. Could this be the mechanism?

This sort of phenomenon could also raise some hairy policy issues-- imagine that we know smoking causes specific epigenetic changes that, if transmitted to a child, increase their risk of some disease. Would we then be justified in banning smoking by anyone who is fertile? Or what if smoking decreases the risk of some disease in your offspring? Would the tobacco companies get back all the money they've paid out in settlements?

Of course, I'm getting way ahead of myself-- no one knows how widespread the transmission of epigenetic variation will be. But this is fascinating stuff, and well worth keeping in mind...