Small epigenetic tags can attach to genes over an organism’s lifetime, blocking environmental influences on how genes are expressed. Specific tags can also be passed from parents to the next generation, thus affecting the inheritance of characteristic traits (phenotypes).
Researchers at IMR in Norway were inspired to study this in fish, after reading about a study on how a mother mouse’s nutrition determines the weight of her offspring.
“Fascinated by this result, we started investigating whether fish phenotypes are also epigenetically influenced by the food they are fed,” they explain in a press release.
“This is of great importance in aquaculture, as tags can either stimulate the development of beneficial traits or possibly hinder the development of robust fish,” the researchers add.
They first used the zebrafish to test if the food had an impact on their offspring. In one experiment, they fed the parent fish a food low in vitamin B, while the offspring received enough vitamin B. They then compared them to a control group where both parents and offspring received enough vitamin B.
When the offspring reached adulthood, the researchers took a closer look at their livers.
“The first thing we noticed was that the experimental group had clearer livers than the control group. Further investigation revealed that liver cells contained more fat, which is associated with poor health,” they explained.
“Furthermore, the analysis showed that genes involved in fat regulation were used differently by the two groups,” the researchers added.
Thousands of tags on the DNA of the offspring had been altered by the amount of vitamin B in the diet consumed by the parents.
“This was the first result to verify that fish feeds can affect epigenetic health of fish progeny, either through changes in inherited labels on DNA or nutrients allocated in the yolk sac. “, they say.
“The result points to an opportunity for the aquaculture industry to epigenetically control the phenotype of the fish it produces, ensuring that parental feeding does not become an old habit that dies hard in their offspring,” they conclude. .
The researchers have since completed a salmon research project in which they addressed four epigenetic questions relevant to the aquaculture industry.
The first was whether the labels and the way genes were used were influenced by the ingredients of the food given to the salmon.
It has been shown that micronutrients in foods can directly affect labels in a dose-dependent manner. This was especially true of genes that play a key role in fat regulation.
If the ingredients of the food do not meet the needs of the fish, the labels can weaken their health.
Epigenetic preparation of pre-smolts
The second question they investigated was whether micronutrients in food affect growth during smoltification by regulating epigenetic tags that regulate gene expression.
Again, we observed that diet affected how genes were used before smoltification. But the impact was greater three months after smoltification, while growth at the post-smolt stage was improved.
These results showed that the diet given at the pre-smolt stage can form the basis of successful smoltification. Epigenetic beacon results will be published later this year.
“For the aquaculture industry, the environmental conditions in which pre-smolts are kept can be of vital importance. If the environmental conditions are not favorable, the tags can become an old habit that dies hard no matter how they are treated in the post-smolt stage,” explain the researchers.
The influence of spawning
The third question investigated was whether the timing of salmon spawning could affect their offspring.
Preliminary results show that micronutrient levels in eggs vary depending on the time of the spawning season. The results suggest that the underpinnings of various phenotypes are conferred by “inheritance” from the mother.
“Inheritance” includes both inherited labels on the mother’s DNA and influence through yolk sac contents, including micronutrient levels. The genetic material of the broodstock from the different spawning seasons studied here came from the same parent line and all the eggs were fertilized by the same father.
For the aquaculture industry, it is possible to adjust the environmental factors (nutrition, diets, nutrient status, temperature and light) to which broodstock are exposed in order to refine the epigenetic tags of the offspring and thus modify specific traits ( phenotypes).
Is there an epigenetic inheritance from the father?
In several model organisms, it has been found that tags inherited from the father can also be passed on to offspring.
“We started by analyzing whether the nutrition of the broodstock sire can affect epigenetic tags in tissue containing DNA that will be passed on to the next generation. The results showed that tags on DNA in gonadal tissue are also highly sensitive to broodstock and sire diet,” they say.
“It is not yet known whether these tags are passed on to the next generation, but based on research involving other model organisms, we expect this. From the above, it is clear that epigenetic research is d ‘great relevance to the aquaculture industry. Among other things, he can uncover ways in which fish farmers can best adapt their fish to cage life by adjusting inherited tags, so that the old habits of their mothers and /or breeding fathers do not die hard in the offspring,” the researchers conclude.