…New research from the University of Maryland provides a surprising possible explanation. For the first time, developmental biologists have observed molecules of double-stranded RNA (dsRNA)—a close cousin of DNA that can silence genes within cells—being passed directly from parent to offspring in the roundworm Caenorhabditis elegans. Importantly, the gene silencing effect created by dsRNA molecules in parents also persisted in their offspring.

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“This is the first time we’ve seen a dsRNA molecule passing from one generation to the next,” said Antony Jose, an assistant professor in the UMD Department of Cell Biology and Molecular Genetics and senior author on the study. “The assumption has been that dsRNA changes the parent’s genetic material and this altered genetic material is transmitted to the next generation. But our observations suggest that RNA is cutting out the middle man.”

Jose and his team, including graduate student and lead author Julia Marré and former research technician Edward Traver, introduced dsRNA marked with a fluorescent label into the circulatory system of C. elegans worms. They then watched as these fluorescent RNA molecules physically moved from the parent’s circulatory system into an egg cell waiting to be fertilized.

In a surprising turn of events, some of the dsRNA molecules could not silence genes in the parent because the dsRNA sequence did not match any of the parent’s genes. But the dsRNA molecules did silence genes in the offspring, when the new worm gained a copy of the matching gene from its other parent. This suggests that, in some cases, gene silencing by dsRNA might be able to skip an entire generation.

“It’s shocking that we can see dsRNA cross generational boundaries. Our results provide a concrete mechanism for how the environment in one generation could affect the next generation,” Jose said. “But it’s doubly surprising to see that a parent can transmit the information to silence a gene it doesn’t have.”….