Environmental Epigenetics by the Father of the Field

Source: Strawbridge Studios, Wikimedia Commons/ CC by 3.0

In a previous post, I cited a talk by Randy Jirtle (left) which touched on the imprinted brain theory and now can add another by the man who could rightly be called the father of environmental epigenetics.

This radio interview is the best account of the subject which I have ever heard and is far and away the most accessible to a non-specialist audience.

Prof Jirtle also explains hormesis. This is the finding that some things which are harmful in large doses (such as ionising radiation) can be positively beneficial in small ones—and certainly questions the no-safe dose mantra of the health and safety industry. Indeed, according to the hygiene hypothesis, a no-safe-dose-of-dirt attitude is positively unsafe!

I only want to add two comments. The first is that hormesis is relevant to the imprinted brain theory also to the extent that it certainly does not suggest that no degree of autism or psychosis is safe or compatible with sanity. On the contrary, its diametric model of mental illness implies that normality represents a certain degree of overlap between autistic and psychotic. Furthermore, it also suggests that genius could be seen as a much greater degree of overlap than normal: a mixture of autistic and psychotic savantism in the same mind.

My second point is that environmental epigenetics is only part of the picture: the other part being developmental epigenetics. Here it is worth pointing out that epigenetic is something of an orphan adjective, being derived from epigenesis, which, as I have explained in previous posts, describes the process of development of the organism from gene to adult. In this interview, Prof Jirtle gives due recognition to developmental epigenesis in his comments about cancer, which is usually a late-onset disorder, (and whose counter-intuitive involvement with the imprinted brain theory I discussed in an earlier post).

With developmental epigenetics in mind, the epigenome might be described as the complete list of genes expressed in human development. When drafting the entire human genome was first mooted, many probably assumed that this is what it would in effect be. But the revelation that expressed genes only represent a tiny fraction of human DNA soon put paid to such a simplistic expectation. Nevertheless, the epigenome as defined above could be listed in the order of its expression. The result would be in effect the program, set of directions, or recipe for producing a human being, and would epitomise developmental epigenetics.

Clearly, once we have the text of the epigenome complete, we will have the Bible of the future. For the time being though, readings of our genome, however you think about it, don't come much better than this!

(With thanks and congratulations to Randy Jirtle.)