The animal kingdom is practically dripping with mucus.
Amphibians, snails and slugs Some of the most famous mucus masters, but even the most isolated microorganisms can cause slime to ooze from time to time.
In our species mucus is produced in the mouth, nose, throat, lungs, intestines, cervix, urinary tract, All for different purposes.
However, the origin of slime in the world is a mystery.
Despite the many similarities between mucus, many forms have evolved in parallel rather than in a branching, tree-like fashion.
Across glands and between mammals, a small study found that many mucus genes do not actually share a common ancestor.
This is unusual because most genes with similar functions come from a common inherited gene passed down from generation to generation because it confers survival benefits.
Even in our species, the genes that code for mucus proteins belong to several families. One secretes gel-forming mucus proteins, while the other produces mucus proteins bound to the cell membrane. There are also “orphan” genes that code for mucus production that don’t quite match up anywhere else.
Each of these distinct breeds It may have evolved independentlyAnd now researchers think they’ve figured out where they came from.
By comparing the genes encoding mucus, known as myosin genes, across 49 mammal species, the team found that non-mucosal proteins can evolve into sticky mucus proteins when short, repeating chains of amino acids (the building blocks of proteins) are added once more.
Among all the myosin genes studied, these random repeats were counted 15 different times.
In other words, some genes in mammals that code for non-Musin proteins tend to stick together over time. These proteins are rich in organic acid Proline They are most likely to turn sticky with generations, according to the authors of the current study.
“I don’t think it was known before protein function evolved in this way, from the acquisition of a protein of repetitive sequences,” He said Evolutionary biologist Omar Kokumin of the University at Buffalo.
“A protein that is not mucin becomes mucin simply by gaining repeats. This is an important means by which evolution creates mud. This is an evolving trick, and we are now documenting that it happens مرارا وتكرارا.”
The authors stumbled upon their discovery by chance while studying human saliva. During the experiments, they noticed that a specific myosin gene in humans showed similarity to another gene seen in mice.
But when they tried to find a common origin, they failed.
The myosin gene in mice appears to have evolved independently, although part of the gene shares a structure seen in genes responsible for human tears, which are not considered mucus.
“We think that somehow this gene tear ends up being reused,” explain Jokkumin.
“It acquires a repeat that confers mucin function, and is now abundantly expressed in the saliva of mice and rats.”
If Gokcumen and colleagues are correct, their findings present scientists with a new mechanism of genetic evolution — the formation of a new genetic function without the usual process of a gene duplication event.
This parallel series of mutations in unrelated genes leading to the same function is an example of convergent evolution (where selective pressure constitutes the same function from unrelated biological origins, such as the wings of bats and birds) that occurs at the genetic level.
“If these fungi keep evolving from non-myosins over and over in different species at different times, that suggests there’s some sort of adaptive pressure that makes them useful,” he said. explain Petar Pajek, an evolutionary geneticist from the University at Buffalo.
“And then, on the other end of the spectrum, maybe if this mechanism goes off the rails — it happens too often or in the wrong tissue — it might potentially lead to diseases like some cancers or mucosal diseases.”
While studying mucus may not seem like the most magical scientific endeavour, it’s hardly an attempt to sniff it out.
The study was published in Scientists’ progress.
