Now, I love me some epigenetics. Feeling bad that I had to miss the Nova special last night called “The Ghost in our Genes.” I decided to sit in on a nurses session about epigenetics and assisted reproductive technologies.
Lee Fallon a former genetics counsellor and consultant made a very nice presentation employing the usual, though not unhelpful analogies, like the idea that epigenetics is akin to highlighting. If the genome is the book of human life, epigenetics provides the cells with context — instructions on how to read genes and how much or how little emphasis should be placed on certain genes in certain cell types.
Increasingly we’ve seen indications that epigenetic patterns set up during pregnancy will influence offspring long into their lives. And there’s been some concern over the past few years that culture media used during IVF or other stresses to the embryos might influence gene imprinting, potentially adding to the incidence of diseases that can be caused by faulty imprinting. Beckwith Wiedemann Syndrome and Angelman Syndrome are the most visible concerns but also intrauterine growth retardation and birth weight issues appear like they might be influenced by epigenetics.
I’ll first state that there’s little data on the role of epigenetic changes in IVF. One scary sounding number is an association of the procedure with a four fold increase in incidence of Angelman is less frightening in face of the fact that it’s population occurrence is on the order of 1 in 16,000.
It’s really the geekier concepts that attract me to this, and that’s the evolutionary role of epigenetics during fertilization. The sperm, from a survival of the species point of view, really doesn’t care where it is as long as it can produce an offspring that will be strong and viable. Thus, imprinting in the sperm’s contribution to the offspring genome tends to favour expression of growth factors.
This drive for growth may benefit baby, but not necessarily mom, who has to provide the nutrients for this growth. If resources are scarce, this might not protect her long term reproductive health. The maternal complement to an embryo’s genome therefore favours more modest growth. Beckwith Wiedemann can be due to chromosomal translocations and mutations, but in some cases of natural pregnancy occurs due to faulty maternal imprinting. With maternal copies of growth factor genes left unsilenced, the babies grow large and often have large organs. So far, all instances of the disorder in IVF children have been due to imprinting.
But while I like getting caught up in the nitty gritty details of how the diseases occur and what it means biologically, this was a session for practicing nurses http://npg-asrm.org/ in the ART field. Shirley Jones of Planned Parenthood offered practical implications of this dense and evolving field of study. During the meeting, she says, she performed an informal survey of her colleagues that run IVF clinics (she told me she talked to about 10), only one of them had anything about the dangers of imprinting disorders in their consent forms and informational materials.
That’s not necessarily a bad thing. There isn’t much evidence at the moment that IVF is doing dangerous things, but it’s something to keep an eye on, and in a litigious society, even one reference to a potential link could be enough for a judge to find in favour of a plaintiff. But this is only the tip of a coming iceberg in relation to reproduction and epigenetics. Fallon warned of a coming “mushroom of recognition of the importance of epigenetics … This is a much broader issue”
Oh and if anyone saw the Nova program. How was it?