The animal kingdom is practically dripping in mucus.
Amphibians, snails and slugs One of the most famous masters of mucus, but even the most lonely microorganism can ooze sticky slime from time to time.
In our species mucus is produced in the mouth, nose, throat, lungs, intestines, cervix, urinary tract, All for a variety of 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 originate from a common ancestor gene that is passed down through generations because it confers survival benefits.
Even in our own species, the genes that encode mucoproteins 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 encode mucus production that don’t fit anywhere else.
Each of these lineages is separate It may have evolved independentlyAnd now researchers think they’ve figured out where they came from.
When comparing mucus-encoding genes, known as mucin 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 (protein building blocks) 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 encode non-Mucinian proteins tend to get thinner over time. These proteins are rich in organic acid Proline They are more likely to align with generations, according to the authors of the current study.
“I don’t think it was previously known that protein function might evolve in this way, from the protein’s acquisition of repetitive sequences,” Says Evolutionary biologist Omar Kokumin of the University at Buffalo.
“The non-myosin protein becomes mucin once repeats are acquired. This is an important method that makes evolution out of the muck. It’s an evolutionary hoax, and we’re now documenting that happening over and over once more.”
The authors came across their discovery when studying human saliva. During the experiments, they noticed that a specific myosin gene in humans had similarities 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 one way or another this gene tear ends up serving another purpose,” explain Jokkumin.
“It acquires the repeats that confer mucin function, and is now abundantly expressed in the saliva of mice and rats.”
If Gokcumen and colleagues are right, their findings offer scientists a new genetic evolutionary mechanism — 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) it 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 Evolutionary geneticist Petar Pajek of the University at Buffalo.
“And then, at the other end of the spectrum, maybe if that mechanism gets derailed — it happens too often, or in the wrong tissues — 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 science progress.
