Researchers at Tel Aviv University said they have found a mechanism in nematodes — worms that are found in all environmental habitats — that allows neurons, or brain cells, to transmit information across generations and control the behavior of the organisms’ progeny.
The findings imply that the activity of the brain, and not only the information hardwired in the DNA, might play a role in what our children inherit.
The researchers said it was not known yet whether any of the work done on the nematodes, also called roundworms, translates to humans.
The results of their study go against one of the basic dogmas of modern biology, called “the second law of biology,” that says that only sperm and eggs affect inherited traits, and the influence of neurons on behavior is not hereditary. Inherited information is thus believed to be isolated from environmental influences.
The mechanism that the researchers have now identified shows instead that neuronal responses — meaning responses from the nervous system — can be transmitted across generations, according to a statement released by the university.
This could mean that the nervous system, which is unique in its ability to plan and organize responses to both environmental and internal cues, helps future generations of progeny.
In their study, the researchers show that the worms’ nervous system controlled the capacity of their progeny to look for food.
The discovery may have major implications for our understanding of heredity and of evolution, said Prof. Oded Rechavi of TAU’s George S. Wise Faculty of Life Sciences and Sagol School of Neuroscience, who led the study. The study was published in the journal Cell on Thursday.
According to the paper, co-authored by Rechavi’s students Rachel Posner and Itai Toker, this is the first time a mechanism has been identified that can transmit neuronal responses — or the activity of the brain — across generations.
The research also identified the way the neurons transmit messages to future generations: via small RNA molecules, whose role is to regulate the function of genes.
The researchers found that these RNA molecules transfer information from the parent neurons to the progeny by regulating the genes in the germ cells (sperm and egg), thus controlling the expression of many genes, leading to changes in physiological processes of the developing organism. In particular, the inheritance of small RNAs controlled by the nervous system affects the food-seeking behavior of the progeny, even three generations down the road.
A ‘holy grail’
“We learned a lot on transgenerational inheritance of small RNA in worms in the last couple of years,” said Toker. “But the discovery of a transgenerational transfer of information from the nervous system is a holy grail.”
“The nervous system is unique in its ability to integrate responses about the environment as well as bodily responses. The idea that it could also control the fate of an organism’s progeny is stunning,” he said.
In their research, the scientists discovered that synthesis of small RNAs in neurons is needed for the worm to be efficiently attracted to odors associated with essential nutrients — to look for food.
These small RNA control genes, including a gene named saeg-2, that are needed for the nervous system to function properly, to generate movement toward food after the scent of food is perceived.
The researchers found that it is the small RNAs produced in the parents’ nervous system that influenced this behavior in their progeny.
In other words, nematodes that were not able to produce small RNAs in their neurons exhibited defective food identification skills. But when the researchers restored the ability to produce small RNAs in neurons, the nematodes moved toward food efficiently once again.
The most interesting part, however, was that worms that descended from ancestors that had these small RNAs had the ability to find food, even if they did not produce small RNAs themselves. And this impact was maintained for multiple generations.
If the findings do indeed translate to humans, “and we don’t know that they would, then it changes the way we think about inheritance,” said Rechavi.
“Many traits might be affected by factors that are epigenetic, meaning not inherited by DNA. Deeper understanding of nonconventional forms of inheritance could be crucial to better understand these conditions and to design better diagnostics and perhaps therapies,” he said in an interview.
Toker added that further studies may want to check if specific neuronal activities can impact the inherited information in a way that would give specific advantages to the progeny.
“Through this route, parents could potentially transmit information that would be beneficial to the progeny,” and therefore potentially influence “an organism’s evolutionary course,” he said.