Mammary Memory

Not only can mammary glands produce milk to feed babies, they can remember if they’ve done it before, according to new research in mice. The findings support anecdotal evidence from human mums that suggested breast milk production is more vigorous with a second baby than with the first. Indeed, mammary glands of mice that had previously been pregnant and raised young (bottom row) responded faster and more robustly to pregnancy hormone treatment – producing a greater density of branching lactation ducts – than did mice that had never been pregnant (top row). It turns out that pregnancy and breastfeeding result in the chemical tweaking – or epigenetic modification – of DNA within mammary gland cells. This modification, in essence, primes the lactation genes for reactivation by a subsequent pregnancy. Exactly how a physiological experience leads to epigenetic memory in cells is mysterious, but it‘s also unlikely to be unique to pregnancy.

Written by Ruth Williams

Ruth Williams

Writer

Ruth is a freelance science journalist based in the US. She's a regular correspondent for The Scientist, and her work has appeared in The Lancet, Nature, Scientific American Mind, BBC Focus and elsewhere. Twitter @rooph

Website

• Image from work by Camila dos Santos and colleagues
• Cold Spring Harbor Laboratory, USA
• Originally published under a Creative Commons Licence (BY 4.0)
• Research published in Cell Reports, May 2015