Epigenetic changes last for generations in toxin-adapted fish, study finds – The Daily Evergreen

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About 80% of epigenetic marks have persisted between generations; future experiments involve the crossing of populations

WITH THE AUTHORIZATION OF PNAS

This image, which appears in the study manuscript, shows the physical differences between freshwater and toxin-adapted Atlantic molly. Fish adapted to toxins have larger heads and gills to accommodate low oxygen water.

WSU researchers found in a study that epigenetic changes in fish living in toxic waters rich in hydrogen sulfide can last for two generations after being transferred to freshwater.

DNA itself – through combinations of four different molecules called base pairs – controls the location of genes. Epigenetic changes turn genes on and off without changing the DNA base pair sequence, said Joanna Kelley, co-principal investigator of the study and associate professor at the WSU School of Biological Sciences.

“Epigenetics are the marks on DNA that are not DNA modifications [sequence] himself, ”Kelley said.

There are several types of epigenetic modifications, including DNA methylation, histone markings and non-coding RNA, said Michael Skinner, co-principal investigator of the study and professor at the School of Science. organic.

The researchers mainly focused on DNA methylation, which occurs when an enzyme adds a small molecule called a methyl group to molecules in the DNA strand. Adding this brand causes genes to be turned off or nonexpressed, Skinner said.

Epigenetic changes determine how different types of cells develop in an organism, he said. For example, skin cells and eye cells contain the same DNA sequence, but have different characteristics because certain genes are turned on or off based on methylation patterns.

A species of fish called the Atlantic molly has two subpopulations. One subpopulation lives in freshwater and the other in natural sources rich in hydrogen sulfide, Kelley said. Hydrogen sulfide is toxic to most organisms.

“These different populations of Atlantic mollies have adapted to hydrogen sulfide,” she said. “Essentially, nature made the experience for us.”

Fish populations have essentially the same DNA sequence, Skinner said. The main differences were epigenetic changes.

“It’s a distinct form of inheritance,” he said. “Epigenetics have been developed in an evolutionary way to respond to the environment, to give it that plasticity, so that the organism has the ability to survive more efficiently in different environments, and this is passed on to subsequent generations.”

The researchers moved the pregnant females from water rich in hydrogen sulfide to fresh water, then waited two generations and drew the blood from the offspring, Kelley said.

According to the study, about 80% of DNA methylation marks persisted between generations.

The discovery means epigenetic changes are fairly stable across generations, Skinner said.

“Epigenetic changes can be how a population might persist in an environment, especially over a short period of time,” Kelley said. “So these epigenetic changes may be the first layer of changes we see in a population as they inhabit a new environment.”

Populations adapted to hydrogen sulfide have larger heads and gills than freshwater populations to help them access oxygen in oxygen-poor water, Kelley said.

In future experiments, Kelley said she hoped to crossbreed both freshwater fish and hydrogen sulfide adapted fish to see how the methylation marks persist.


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