Folate and sperm:
There is a cloud on her horizon no bigger than a man’s hand. (Poisoned Inheritance ECONOMIST vol. 409 no. 8866 December 14, 2013 page 85 reviewing work by Sarah Kimmins and colleagues at McGill University, Montreal published in Nature Communications.) Where it goes from here is anybody’s guess but I am optimistic for a downpour.
It has long been known that if mothers are denied adequate folic acid in their diet during early pregnancy their babies have an increased chance of birth defects. What has now been shown through elegant work is that if male rats are denied folic acid then their fertility is reduced, their offspring have a greater incidence of birth defects and as the pups go on in life they have an increased likelihood of cancer, diabetes, autism and schizophrenia. (Of course a rat can’t tell you what it’s hallucinations are, but you can observe things like working memory, selective attention, “set shifting,” social interaction and startle inhibition: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1764543/ ) These things seem to be on the rise in rich countries although folate deficiency is presumably not; they add folic acid to things like bread.
Say, “Folate,” and I’ll think, “Affects methylation of DNA and has epigenetic effects,” and say, “That’s my game.”
It’s not yet clear whether men should take folate supplements before attempting to become fathers. The relevant methylation of their sperm could happen just before ejaculation or it could happen during early embryonic development. I’m sure the answer will be coming out of Montreal pretty soon. The workers there have diligently run down the site where methylation of the sperm takes place, and sure enough some of them are implicated in the diseases in question. What I doubt they ask (although I’ll suggest they ask, my letter being included below) is whether the problem is really always just a lack of methylation or is it a mismatch between the maternal methylation pattern and the paternal. It might be indeed, since there is certainly a steadily increasing mismatch between methylation patterns of couples in our stampede to outbreed.
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