How a Mother’s Age Influences Her Offspring Remains a Genetic Mystery—These Tiny Aquatic Animals May Have Answers

New research involving tiny aquatic animals known as rotifers is providing scientists with a unique look at how information about maternal age may be passed from one generation to its offspring. The findings offer insights into the ways a mother’s age can influence factors that range from health and lifespan to the behavior and even reproductive success of her offspring. This phenomenon, known as maternal age effects, has been documented throughout the animal kingdom—observed in everything from invertebrates to large land mammals like elephants, and even humans. For their research, Gribble and her colleagues have focused on Brachionus manjavacas rotifers, a variety of microscopic aquatic creatures whose rapid reproduction abilities allow scientists a unique opportunity to study biological changes that occur across multiple generations. The new findings resulted from work undertaken in Gribble’s laboratory by researcher Alyssa Liguori, which looked at two different genotypes within a single species of rotifer. The premise was simple: if mutations or cellular damage were what was behind maternal age effects, the consequences would likely be shown to worsen progressively across generations. However, what the team found instead was that such effects could be reversed, and in some cases, within a single generation. The fact that this can occur so rapidly seems to imply that the underlying mechanism at play involves changes in the way genes are expressed, as opposed to alterations in the actual genetic code, as suggested in the past. The team is now exploring whether histone modifications—essentially chemical changes that impact proteins that are encased with DNA, which can influence whether particular genes become activated, or suppressed—could play a key role in transmitting information about maternal age from one generation to the next. Additionally, the researchers are now looking at whether mitochondrial DNA (mDNA), known to generally be inherited from an offspring’s mother, could play a key role in helping transmit information about maternal age from one generation to the next. One intriguing aspect of the recent research that Gribble emphasizes involves how one rotifer strain seemed to produce offspring from older mothers, which actually exhibited longer lifespans. This may suggest that some genetic variants could help to protect against, or possibly even reverse, factors that are generally negatively associated with advanced maternal age. Still, a few mysteries remain, such as what exactly causes maternal age effects to remain so widespread, especially if they often reduce an offspring’s evolutionary fitness. Gribble has an idea: she suspects that natural selection may provide at least part of the answer, since reproduction in rotifers occurs relatively early in life. This could mean that evolutionary pressures that eliminate harmful effects that may arise from reproduction at advanced ages could be comparatively weak. Ultimately, the team believes their research may help to illuminate a much broader question: how the experiences and biological state of one generation influence those that follow. “It’s not just about what’s in your genome as an individual,” Gribble said, adding that this is mainly because “your health potentially depends on the health and environment of your mom and grandmother and great-grandmother.” Fundamentally, if researchers can identify the mechanisms behind maternal age effects in rotifers, these unassuming aquatic creatures could help to significantly advance our understanding of the ways biological information is carried across generations, potentially offering new insights into human health and precision medicine. The team’s findings were detailed in a new paper, “Transgenerational and Intergenerational Maternal Age Effects Exhibit Complex, Genotype-Specific Patterns of Inheritance,” which appeared in The American Naturalist.

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