A Mother's Age Can Shape Her Offspring Without Changing Their DNA, Rotifer Study Finds

A mother's age can influence the traits and behaviour of her offspring across humans and many other animals, a phenomenon researchers call maternal age effects. According to Kristin Gribble of the Marine Biological Laboratory, nearly all forms of life show some level of the effect, from invertebrates up through elephants, primates and other mammals, and most are negative effects linked to advanced maternal age. How this information passes from mother to offspring has remained unclear.

To probe the mechanism, Gribble's lab studies rotifers, tiny aquatic animals that reproduce quickly and are well suited to laboratory work. Work by postdoctoral scientist Alyssa Liguori, now at SUNY-New Paltz, examined two genotypes of one rotifer species and found that the effects tied to maternal age did not grow steadily stronger with each generation. Instead they could be reversed within a single generation. That rapid reversal argues against the long-standing idea that maternal age effects come mainly from the gradual build-up of cellular damage or DNA mutations that accompany ageing.

The findings point instead to an epigenetic process involving histone modifications, chemical changes to the proteins that DNA wraps around, which can switch genes on or off without altering the DNA sequence. Gribble's team is now testing whether these modifications are responsible, and is also considering whether mitochondrial DNA, usually inherited from the mother, plays a role. Genetic differences may also shape how strongly offspring are affected: in one strain, offspring of older mothers lived longer, hinting at a protective genetic mechanism.

Why the effect persists across so many species is an evolutionary puzzle, since offspring of older mothers often live shorter lives and reproduce less. Gribble suggests natural selection weakens later in life, especially in rotifers, which do most of their reproducing when young, so there is little pressure favouring traits that help older females produce especially fit young.