Are your genetics the way they are because your mother was on a diet shortly before she became pregnant with you? Or maybe it’s because your grandmother was exposed to a large amount of lead early in her life?
Studies suggest that what happens in one generation, no matter how small, can have lasting effects on future generations. These effects result from epigenetic changes that occur in response to the environment and turn genes on or off without altering the genome or DNA sequence. But, unraveling the mystery of how experiences can cause inheritable changes has been much easier said than done. Previously, scientists did not have a simple way to study and track the phenomenon through generations.
Now, in a new paper published in Nature Communications, researchers from the University of Maryland have demonstrated a simple mating-based method that shows how permanent epigenetic changes can last for more than 300 generations.
The research team, led by Antony Jose, began exploring epigenetic changes with Caenorhabditis elegans (C. elegans) in 2013 when they noticed something unusual about one of the worms’ genes. Those bred to carry a gene called T, which produces fluorescent proteins, sometimes glowed and sometimes didn't. This was especially puzzling to the researchers since the “glowers” and “non-glowers” had nearly identical DNA.
For their new study, the researchers conducted C. elegan breeding experiments in which only the mother or the father carried the T fluorescent gene. While they expected all offspring to glow regardless of which parent carried the gene, that was not the case. Instead, if the mother carried the fluorescent gene, the offspring always glowed—meaning the gene was always turned on. But, when the father carried the gene, the offspring weakly glowed or did not glow at all.
"We found that there are these RNA-based signals controlling gene expression," said Jose. "Some of these signals silence the gene and some of them are protective signals that prevent silencing. These signals are duking it out as the offspring develop. When the gene comes from the mother, the protective signal always wins, but when the gene comes from the father, the silencing signal almost always wins."
When the silencing signal wins, the gene is silenced for good, or for at least 300 generations, which is how long Jose and his colleagues followed their laboratory-bred worms.
However, the research team hasn’t yet discovered why the silencing signal only wins sometimes, or why this set of genes reacts differently than most other genes—which typically bounce back quickly and are expressed within just a few generations.
"The two big advantages we now have from this work are that this long-lasting epigenetic change is easy to induce through mating, and that it occurs at the level of a single gene," said Jose. "Now we can manipulate this gene and control everything about it, which will allow us to determine what characteristics make a gene susceptible or resistant to heritable epigenetic change."