A sea anemone named Nematostella vectensis has rewritten our understanding of heredity—and it did so by losing most of what should have made it tick. When scientists experimentally removed DNA methylation, a chemical modification that regulates genes without changing the DNA itself, the anemone developed normally. This surprising finding, published in Nature Ecology & Evolution by Lan Xu and colleagues, reveals that inheritance is far more flexible than the central dogma of genetics suggests.
For decades, biology textbooks taught a clean story: DNA carries instructions, and those instructions stay the same across generations. But genes do far more than simply exist—they turn on and off in response to signals from cells and environments. This switching happens through epigenetics, modifications like DNA methylation that sit atop the genetic code like a vast control panel. Mammals carefully erase most of these epigenetic marks after fertilization to give each generation a fresh start. But invertebrates like sea anemones, worms, corals, and sea urchins lack this extensive resetting. The implications are profound.
When the researchers stripped away methylation patterns in Nematostella, they expected chaos. Instead, something unexpected emerged: the animals survived, but hidden "jumping genes"—selfish genetic elements that normally sit dormant—began activating. These parasitic DNA sequences, embedded within active genes, can insert themselves into crucial regions and destabilize the genome. Methylation, it turns out, wasn't primarily controlling which genes were on or off in sea anemones. It was acting as a molecular security system, keeping these genomic troublemakers in check.
Even more striking was what happened next. The abnormal methylation patterns persisted in offspring, altering how their genes switched on and off. Dr. Alex de Mendoza, Reader in Evolutionary Epigenomics at Queen Mary, describes the significance plainly: "Because these animals lack the extensive epigenetic resetting that occurs after fertilization in mammals, some abnormal methylation states persisted in the offspring. These inherited epigenetic changes altered how genes are switched on in the next generation, demonstrating that experimentally induced epigenetic variation can be transmitted across generations in an animal."
This opens a window into evolutionary history. The ancestral role of DNA methylation in animals appears to have been genome protection, not development. Over millions of years, mammals evolved to co-opt this same molecular system for elaborate purposes—regulating development, silencing one X chromosome in females, and controlling thousands of other processes. But the ancient function remained.
Perhaps most intriguingly, incomplete epigenetic resetting in invertebrates creates a hidden layer of heritable variation that requires no changes to DNA at all. Evolution typically works on genetic mutations—random changes that either help or harm survival. But this mechanism suggests that organisms can accumulate and transmit epigenetic variation across generations, creating raw material for evolution to act upon without altering the genetic sequence. A sea anemone without most of its methylation patterns still developed successfully, hinting at just how much flexibility life contains beneath the surface. The findings remind us that heredity operates on multiple levels, and that the oldest systems in our cells may still hold secrets about how life changes and persists.