September 30, 2022

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Nature: Satellite DNA plays a vital role in early embryonic development

Nature: Satellite DNA plays a vital role in early embryonic development



 

Nature: Satellite DNA plays a vital role in early embryonic development.

 

All organisms have DNA, the genetic material that provides the blueprint for life. The long, double-helix-shaped DNA molecules in the body’s cells are first translated into RNA molecules and then into proteins, ensuring the functioning of the cell and the entire organism.

But a large portion of DNA is also not used to make proteins, and is called “junk DNA” because their function has long been unclear.

 

However, in a new study, researchers from the Radboud University Medical Center in the Netherlands reveal that a certain type of junk DNA (called satellite DNA) found in mosquitoes that repeats dozens of times in the early stages of mosquito embryos plays a vital role in development.

The related research results were recently published in the journal Nature with the title “A satellite repeat-derived piRNA controls embryonic development of Aedes“.

 

Nature: Satellite DNA plays a vital role in early embryonic development

Image from Nature, 2020, doi:10.1038/s41586-020-2159-2.

 

 

Early development

in all animals — in this new study, in particular the yellow fever mosquito vector Aedes aegypti — is composed of various cell types that form different tissues and organs, all of which Both are produced by a fertilized egg.

It’s a complex process; to ensure that a fertilized egg successfully develops into an embryo, the mother provides not only half of the genetic DNA, but also additional protein and RNA for the egg.

 

These RNAs and proteins are essential complements because these molecules direct the first cell division of the fertilized egg. Only after multiple cell divisions does the mother produce the proteins and RNAs that drive further development.

At the same time, the additional proteins and RNAs provided by the mother must be degraded in time so as not to interfere with the subsequent development of the mosquito.

 

 

Corresponding author of the coordinating RNA

Ronald van Rij from the Radboud University Medical Center, and his team discovered that slipping DNA (stuttering DNA, which refers to the process of polymerases in the replication of DNA segments that contain a large number of repeating nucleotides or repeating sequences— That is, satellite DNA—is prone to slippage) to produce two kinds of small RNA molecules.

This occurs during the earliest stages of mosquito embryonic development. However, these small RNA molecules do not produce any protein.

These small RNA molecules regulate the activity of other protein-coding RNA fragments. In this case, they bind to the parent’s RNA molecule, which is then degraded.

This step is very important: the absence of these “regulatory RNAs” will lead to the persistence of maternal RNA molecules, which will disrupt the subsequent development of the embryo.

 

 

Satellite and dinosaur

Van Rij highlights how extraordinary this new study is. “In this study, we made some completely unexpected discoveries.

Although satellite DNA was first discovered sixty years ago, very little was known about its function. In this study, we found that it actually It has a very important function during a critical stage of development.”

 

Furthermore, from an evolutionary point of view, this mechanism is clearly quite ancient. “Together with researchers from Wageningen University, we studied a large group of mosquito species,” says Van Rij. “This led us to discover that this satellite DNA and specific regulatory RNAs originated 200 million years ago, i.e.

The late Triassic, an era that coincides with the rise of dinosaurs. I think it’s good that these small RNAs haven’t changed for so long. It also shows, in particular, that they have important functions.”

 

 

From mosquitoes to humans?

The first steps of embryonic development in different animal species have obvious similarities, but they differ considerably at the molecular level.

This particular piece of slippery DNA is not found in humans, but it is possible that other satellite DNAs play a role in embryonic development in humans or other animals.

 

 

Background: A serendipitous discovery

This study builds upon a serendipitous discovery. Aedes aegypti is a mosquito that transmits important pathogens such as dengue virus and Zika virus.

Van Rij’s research team studied how these types of viruses are transmitted by mosquitoes. “We’ve done a lot of research on the mosquito’s immune system that fights viruses,” Van Rij said. “This immune system recognizes the RNA of the virus and breaks it down into small pieces.

When analyzing the RNA fragments in cells infected with the virus, , Pascal Miesen and Rebecca Halbach accidentally discovered small RNA molecules that did not come from viruses.

These small RNAs turned out to be produced by the satellite DNA of the cell itself. We found this to be remarkable and decided to investigate further. After 5 years of research, We finally have these findings.”

 

 

 

Reference:

1. Rebecca Halbach et al. A satellite repeat-derived piRNA controls embryonic development of Aedes. Nature, 2020, doi:10.1038/s41586-020-2159-2.

2.Stuttering DNA orchestrates the start of the mosquito’s life

Nature: Satellite DNA plays a vital role in early embryonic development

(source:internet, reference only)


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