With small beady black eyes and mottled gray fur, the mice born in a recent experiment in Hong Kong are completely different from other mice of their kind, and in fact, different from other animals.
But despite their fundamental differences, they couldn’t seem more ordinary, a fact that reveals surprising truths about our evolutionary history.
The mice had genes from a single-celled microorganism called Brassica napus. chooflagellates. Although microorganisms are not themselves animals, they are closely related to animals, largely unchanged from the era before the existence of complex multicellular organisms.
Remarkably, the successful selection of chonoflagellate genes in an animal as complex and multicellular as the mouse provides us with new insights into the evolutionary origins of animal traits.
Animals have a feature known as pluripotency. The ability of embryonic stem cells to differentiate and develop into the various tissues that make up a fully developed organism. Despite lacking this talent, chonoflagellates have their own version of the responsible gene. Animal pluripotency.
By swapping the mouse gene with the version found in choanoflagellates, the researchers were able to determine how similar the two function.
“By successfully creating mice using molecular tools derived from unicellular relatives, we are witnessing an incredible continuity of function across nearly a billion years of evolution.” says geneticist Alex de Mendoza. He received his Ph.D. from Queen Mary University, UK.
“This study shows that the key genes involved in stem cell formation may be much older than the stem cells themselves, perhaps helping to pave the way to the multicellular organisms we see today. It suggests something.”
Pluripotency is thought to have emerged with the emergence of multicellular animals approximately 700 million years ago, so transcription factors related to stem cell pluripotency, socks and POU The family is thought to be limited to multicellular animals.
However, previous studies conducted on microorganisms adjacent to animals have shown that origin pluripotent Before multicellularity. If this is true, it could be one of the driving forces, rather than a result, of animal evolution.
The choanoflagellate Sox gene has traits similar to those found in the mammalian Sox2 gene. In mice, Sox2 interacts with a POU member called Oct4. However, the choanoflagellate POU gene is unable to generate pluripotent stem cells.
A research team led by Ya Gao and Daisylyn Senna Tan from the University of Hong Kong and Mathias Girbig from the Max Planck Institute for Terrestrial Microbiology in Germany has investigated what happens when the mammalian Sox2 gene is replaced with the choanoflagellate Sox gene. I wanted to know.
They grew cloned mouse stem cells and reprogrammed their genomes, replacing Sox2 with choanoflagellate Sox. These cells were injected into mouse blastocysts and then implanted. false pregnancy Mouse surrogates are conceived, given birth, and housed in a nurturing environment.
Chimeric puppies are born with different characteristics based on their spliced genetics. Obviously they were rats. However, they had black eyes and black fur spots, indicating their mixed genetics. Otherwise they were pretty normal. This suggests that the choanoflagellate Sox gene was able to create developmentally compatible stem cells in mice.
This suggests that tools to generate multipotency developed in choanoflagellates before the emergence of multicellularity.
“Although choanoflagellates do not have stem cells and are unicellular organisms, they do have these genes, which probably control fundamental cellular processes that multicellular animals later reused to build complex bodies. It is thought that. de mendoza says.
This finding suggests that the Sox transcription factor of hundreds of millions of years ago in choanoflagellates was biochemically similar to Sox genes that play important functions in today’s multicellular organisms. On the other hand, the inability of the choanoflagellate POU to produce pluripotent stem cells suggests that POU members needed to undergo modification to play the role they currently play in pluripotency.
These results could have implications for stem cell research and treatments, the researchers said. And they add interesting complexity to the story of how life diversified on Earth.
“Our data clearly demonstrate that two major gene families involved in vertebrate pluripotency and key developmental genes across animals were already present before the origin of multicellularity. Masu.” The team writes in their paper:.
“Ultimately, their biochemical abilities were harnessed to construct one of the cell types that define complex multicellular entities.”
This research nature communications.
