The experiment focused on epigenetics, examining how chemical signals regulate gene activity without altering the genetic code. Within each cell, DNA wraps around proteins called histones, which receive chemical signals that determine which genes remain active or silenced.
To identify the mechanism, the researchers transiently altered the distribution of the H3K27me3 signal in the worms by having the animals manufacture a modified version of a histone. This initial intervention noticeably reduced animal fertility. Under normal conditions, each specimen produces about 300 offspring, but the affected worms produced only 50 to 100 descendants. Descendants selected to continue the experiment no longer carried the genetic modification that caused the initial alteration, yet they kept both the unusual chemical signal distribution and the reduced fertility.
Doctoral student Isa Özdemir and postdoctoral researcher François-Xavier Stubbe stated that the changes in gene regulation and the fertility problems persisted for at least 15 generations.
Two Distinct Proteins Control Transgenerational Transmission
The transmission process relies on two consecutive phases involving different proteins that act at different times. First, a protein named SET-32 adds a transient chemical signal to the histones, which is necessary for passing the altered state from the exposed generation to their offspring. Second, a protein called MES-4 preserves the effect across subsequent camadas. Özdemir and Stubbe explained that maintaining an epigenetic state depends on a succession of specialized mechanisms rather than a single process.
The transmission did not occur identically across all test subjects. In each generation, some animals recovered their normal gene regulation patterns and fertility, while others maintained the alteration. Between 25 percent and 40 percent of descendants from low-fertility specimens preserved that specific trait throughout the observed generations. This variation happens because two competing processes operate simultaneously: one replicates the altered state while the other reconstructs the normal pattern, making the change unstable and reversible in individual specimens and broods.
Laboratory Findings and Biological Implications
The study clarifies basic mechanisms of gene regulation and suggests that this form of transmission could act as an additional mechanism for organisms to respond to changing environments. However, the researchers emphasize that the experiment did not involve humans and does not demonstrate that the same phenomenon occurs in human health.
