Home » Sterile Mice Are Now Fertile As They Can Produce Rat Sperm

Sterile Mice Are Now Fertile As They Can Produce Rat Sperm

by Coffee Table Science

Researchers at the ETH University, Zurich, Switzerland, have genetically engineered animals that can produce sperm despite being sterile (infertile). This research opens the door to breeding animals using their genetic material (DNA). 

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What are sterile mice?

Sterile mice are hybrid mice or the offspring of two different parents (rats and mice) that are genetically modified and created in laboratories for research purposes. They have more robust genes than their parents and tend to have special qualities like longer lifespan, strong immunity, unique physical characteristics etc. However, they are infertile and can’t produce sex cells, eggs or sperm. 

The new research showed that it is possible to produce sex (germ) cells in hybrid animals, in this case, rat sperms in sterile hybrid mice. While the technology still needs improvement to add germ cells of one animal species into embryos of another. This step can be a big move to prevent endangered species from extinction. 

“Our study shows that we can use sterile animals as hosts for the generation of germ cells from other animal species,” said Ori Bar-Nur, a biologist at ETH Zurich and the study’s lead author. “Aside from a conceptual advancement, this notion can be utilised to produce endangered animal species gametes inside more prevalent animals. Other implications may involve an improved method to produce rat transgenic models for biomedical research.” 

How did scientists produce sperm in sterile mice?

The team used pluripotent stem cells (PSCs). These cells can produce different types of cells in the body, which form essential body organs like respiratory, digestive systems, etc. However, producing gametes (sperms or eggs) from PSCs is challenging. In previous experiments, researchers used the blastocyst complementation technique to develop rat organs in mice by injecting rat PSCs into the mouse embryos. They used the same way to create rat sperm in mice carrying genetic mutations (hybrid mice). 

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During the process, the responsible gene for sperm production mutated in the mouse embryo as both mouse and rat cells were growing together. This resulted in reproductive chimaeras, mouse-rat offspring. The male chimaeras developed testes, and the sperms could fertilise female rat eggs. However, the embryo did not give rise to a live offspring. Further, these sperms were non-motile, and their potency to fertilise rat eggs was low compared to rat sperms. 

How can this technology be used in the future?

Though the current experiment showed some negative results, researchers believe this technique can help produce sperms of a specific animal species in another by combining their PSCs in an artificial genetically engineered organism like chimaeras. This technology can restore the number of endangered animal species if they are unable to produce healthy offspring. 

In the future, researchers aim to develop animals from rat sperm that have been produced in chimaeras to support animal conservation. “We will need to improve the technique and demonstrate that rat sperm produced in mice can give rise to adult rats when fertilising rat eggs,” said Bar-Nur. 

The findings have been published in the journal Stem Cell Reports

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