Mucus-producing mucin proteins have repeatedly and independently emerged in mammals, possibly through co-option of existing proteins into slime factories
The proteins that produce mucus may actually have evolved in at the very least 15 independent instances in mammals, possibly by co-opting existing proteins into mucus-producers.
From the gooey saliva of your dog to the slippery coating of a slug, mucus is just about everywhere in the pet kingdom. Almost every animal, even yeast and bacteria have mucus, says Omer Gokcumen at the University at Buffalo in NY State. Its an essential-for-life sort of substance.
Mammals produce mucus through toilet-brush-shaped proteins called mucins, which lend gooeyness and slip to fluids. Most animals have numerous mucins whose slimy products combine to generate the proper thickness and slickness in various parts of the body.
Gokcumen first investigated mucins after making an urgent discovery in mice. He pointed out that the principal mucin in human saliva, called MUC7, is absent in the rodents. Conversely, mice saliva is thickened with a mucin called MUC10 that humans lack. When he investigated, he and his team found both mucins were evolutionarily unrelated a rest from the most common trend where animals share proteins from the common ancestral gene.
Then, the team found another surprise. MUC10, the mouse-saliva protein, looked remarkably like the protein that lubricates human tears, called PROL1. Unlike the mouse mucin, PROL1 lacked repetitions of specific proteins, the sugar-coated blocks of a protein.
We’d both of these different mucins with two different evolutionary origins. Were like, thats awesome, and we wish to know if this is really happening elsewhere or is this exactly like among those weird, finicky, evolutionary once-in-a-lifetime stories? says Gokcumen.
By way of a genetic analysis of 49 different mammals, from pangolins to rhinoceros, the team could pinpoint 15 distinct mucins that werent within other species, which Gokcumen calls orphan mucins. Finding one new mucin could have been surprising, he says, but finding over twelve was a shock.[These mucins] dont even exist in other species. Theyre just specific to cows, just specific to ferrets, just specific to humans, says Gokcumen. The key reason why [mucins] are weird is they’re not from the single genetic ancestor, however they appear to be evolving independently in various lineages in various ways, he says.
The team suspects the brand new mucins are co-opted from existing proteins. By duplicating parts of specific proteins, the proteins grow longer and transform right into a slime-producing mucin.
Most species with original mucins have just one single, but others were standouts: ferrets have a complete of five mucins unique in their mind alone.
Gokcumen anticipates there are many unique mucins left to find. Next, he hopes to research just how many times the slimy stuff has evolved in slugs and snails.
Journal reference: Science Advances, DOI: 10.1126/sciadv.abm8757
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