Worm experiments reveal how epigenetic effects persist across generations

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Every cell in an organism contains the same DNA, which carries all the instructions needed for it to function. Yet cells do not all use the same genes: A nerve cell, for example, does not activate the same genes as a muscle cell.

Epigenetics refers to the mechanisms that allow gene activity to be modulated without changing the DNA sequence. These mechanisms involve, among other things, subtle and reversible modifications to the proteins that package and organize DNA. They can alter how DNA is organized—but not its content—and affect the accessibility of genes to cellular proteins.

Some of these modifications can persist when cells divide and, in some cases, can be passed on to the next generation. To determine how long an epigenetic change can persist across generations, the team led by Florian Steiner, a professor in the Department of Molecular and Cellular Biology at the UNIGE's Faculty of Science, studied Caenorhabditis elegans. This tiny worm has become a major model organism in biology, thanks to the many discoveries of fundamental biological mechanisms it has enabled.

Its rapid reproduction also makes it possible to follow several generations easily in the laboratory. The study is published in The EMBO Journal. The scientists focused on a modification of histones—the proteins around which DNA is wrapped—known as H3K27me3.

This epigenetic mark is associated with the repression of certain genes, meaning that it helps prevent them from being expressed. The researchers temporarily disrupted the distribution of H3K27me3 by causing the worms to express a mutated form of the H3.3 histone. This initial disruption led, among other effects, to reduced fertility, from around 300 offspring per parent to 100 or even 50.

However, it was not genetically inherited: The descendants were genetically normal. The scientists then followed gene regulation and fertility from one generation to the next. "Surprisingly, we found that the effects did not disappear when the initial trigger was gone.