Mom's eggs typically get most of the credit for the miracle of life. But now researchers have found sperm may pass nutritional information — not encoded in the DNA — from generation to generation.
In the study, a host of metabolic changes showed up in the livers of mice whose fathers were fed a low-protein diet.
"The take-away is that we are more than just our genes," said study researcher Oliver Rando of the University of Massachusetts Medical School. "And there are many ways our parents can 'tell' us things."
The underlying sequence of base pairs in the mice's genes did not change. (A base pair consists of two nucleotide molecules that sit opposite one another on complementary strands of DNA.) Rather, chemical modifications occurred that alter the way the genes are expressed, or how they function in the mice. The phenomenon is called epigenetics, when the genes themselves don't change but their function does.
These chemical changes, like the genes themselves, are also inherited, and according to the researchers, their results increase evidence that this external alteration of the genetic code may play an important role in passing environmental information on to the next generation.
This idea isn't new. In humans, epidemiological studies indicate that if your paternal grandfather went hungry, you will be at a greater risk of developing obesity and cardiovascular disease, and a study in rats published earlier this year found that fathers on a high-fat diet pass health problems on to their daughters.
In the current study, published today (Dec. 23) in the journal Cell, the researchers fed the father mice a low-protein diet from the time they were weaned until they reached sexual maturity. They found that the expression of hundreds of genes was altered in these males' offspring. These changes included a chemical modification associated with reducing the activity of a gene involved in the synthesis of lipids and cholesterol in the liver.
"It's consistent with the idea that when parents go hungry, it's best for offspring to hoard calories," Rando said.
It is not yet clear how the chemical modifications are encoded and passed on from the father. However, these results, plus those of other studies, suggest rethinking basic approaches to studying complex diseases, such as diabetes, heart disease or alcoholism, the researchers wrote.
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