Tuesday, October 4, 2022
Home SCIENCE What is mucus made of? A look at the evolution of...

What is mucus made of? A look at the evolution of slime.

This article originally appeared on The conversation.

Omer Gokcumen is Associate Professor of Biological Sciences, buffalo university.

Slime is everywhere. It shapes the consistency of your bodily fluids, from the saliva in your mouth to the goo that coats your organs. Protects you against pathogens, including the coronaviruswhile creating a home in your mouth for billions of friendly bacteria. Aid slugs have spiderman sex hanging from the walls, the hagfish turn into water into a sticky, rapidly expanding substance, lampreys filter their foodY swifts build nests.

But while slime is essential to all forms of complex life, its evolutionary origins remain murky.

I’m in evolutionary geneticist that studies how humans and their genomes evolve. Along with my colleagues, including my long-time collaborator Stephen Ruhl and my student petar pajicwe tackle this evolutionary puzzle in our recently published article. We started by investigating how salivary slime is produced in different species. What we found was that the slime opens a window into the role repetitive DNA plays in the mysteries of evolution.

What are mucins?

slime is made of proteins called mucins, which are containers for sugar molecules. These sugars are the key overseers for making things slimy.

Unlike other proteins, which normally have intricate 3D shapes, mucins often take the form of long, stiff rods. Sugar molecules bind along the rods, creating complex brush-like structures.

Mucins have a long protein backbone with sugars sticking out along ilength of ts. Reproduced from Petrou 2018 with permission from the Royal Society of Chemistry

This association between the building blocks of proteins and the sugars attached to them, repeated over and over again, is essential to the properties of mucins. These structures can adhere to other mucins and microbes, changing the physical properties of the fluids that surround them into a sticky, viscous substance.

slime evolution

Despite the remarkable properties mucins have and their essential role in biology, how they evolved has eluded scientists.

To begin uncovering the evolutionary origins of mucins, my colleagues and I began by looking for common genetic ancestors for mucins in 49 mammalian species. after all, evolution often plays but rarely inventories. The easiest way for a new gene to evolve is copying and pasting an existing one and making minor changes to the new copy to suit the environmental circumstances. The chances of a species independently inventing a complex mucin from scratch are astronomically small. Our research team was certain that copying and pasting existing mucin genes that are then tailored to the needs of a particular species was the main driver of mucin evolution.

But our initial assumptions turned out to be incomplete. Copying and pasting mucin genes into a genome should lead to daughter genes that have similarities to each other. Although some mucins fit our criteria, an earlier study reviewed all known genes encoding mucins in people and found a number of “orphan” mucins They do not belong to any gene family. They exist alone in the vast landscape of the human genome.

Diagram depicting three hypotheses researchers considered for mucin evolution: gene duplication, coding sequence evolution of already repeated non-coding regions of the genome, and gain of existing protein repeats
The researchers considered three possible ways mucins could have evolved: duplicating the entire gene, creating a new gene from scratch, or adding repetitive genetic sequences from existing proteins. From Pajic et al., Science Advances Volume 8, eabm8757 (2022)

We then focused on searching for such orphan genes in the genomes of dozens of species in genetic databases. We found 15 instances of novel mucin genes that evolved in different mammals, with no connection to known mucin genes.

However, further research revealed that these mucin genes do have relatives after all, since they share ancestry with other rod-like proteins. rich in the amino acid prolinewhich are commonly found in saliva. However, these proline-rich proteins do not have the key repeating protein structures that help mucins bind to sugar molecules.

We hypothesized that these proline-rich proteins might undergo “mucinization” by repeatedly adding proteins that bind to sugar molecules, called glycoproteins. To test this, we compared the sequences of genes encoding mucins and genes encoding proline-rich proteins in different mammals, including people. We found that the sequences were very similar. The only difference was the presence of repeated segments of glycoproteins in mucins. What this meant is that certain proteins could be transformed into mucins simply by adding copies of these repeating segments.

repetitive DNA and evolution

Our findings reveal the diversity of mucins in all sorts of creatures, opening a view into the slimy playing field of evolutionary adaptation.

Researchers often ignore repetitive genetic sequences because they rarely occur within genes that code for proteins that perform many biological functions in cells. But in the case of mucins, creating repeated sequences from scratch turns out to be a major driver for their evolution. our previous work on primates suggests that the number of repeating sugar-binding segments in a given mucin may be the factor that determines its differences from others.

It is possible that the addition of repetitive genetic sequences may also discreetly shape other functions throughout the genome. In fact, look for tandem repeats are a common type of mutation in the human genome, and recent studies they hint at their undiscovered role in biological variation between people.

The mucins in a snail’s slime trail have similar biological properties to the mucus in its body. deposit photos

Mucins and human health

Understanding how mucins work will also help researchers better understand a number of diseases.

When mucins don’t work properly, they can cause disease. Malfunctioning people CFTR gene develop cystic fibrosis, where their bodies are unable to remove mucus from their lungs and make it difficult to breathe. Defective regulation of mucin is also related to cancer development.

Although it may not be obvious, it is likely that you have a personal connection to mucins. Two years ago, I visited my mother after her cancer diagnosis. The rain had just ended and the streets of Istanbul turned into a bustling town of eerily large snails. During a short walk with my mother, I picked up one of those snails with fascination, much to her horror.

I didn’t have the heart to tell you that the biological mechanism that allows these impressive creatures to move is the same one that helps the tumor in their lungs to grow. He reminded me of the words of the scientist Michael Faraday: “No matter what you look at, if you look at it closely enough, you are involved in the entire universe.”

The conversation


Nobel Prize in Physiology or Medicine will be awarded today

The Nobel Prize in Physiology or Medicine will be awarded by the Nobel Assembly in Sweden on Monday, the first of several prizes to...

Unearthing everyday life at an ancient site in Greece

As the sun reached its peak, waves of heat rose from the cypress-clad hills around me. The turquoise waters of the Ionian Sea...


Please enter your comment!
Please enter your name here

- Advertisment -

Most Popular

Progressive See extremism only elsewhere

The 9/11 elections in Sweden shocked intellectuals across the West. The Sweden Democrats, a nationalist-populist party founded in 1988 with neo-Nazi loyalties but...

Dr. Oz Closes in on Fetterman in Pennsylvania Senate Race: POLL

Republican candidate Dr. Mehmet Oz is narrowing the Democratic lieutenant's lead in the polls. government John Fetterman in the Pennsylvania Senate race, according...

In a new book, Nikki Haley criticizes the ‘hypocrisy’ of modern feminism

"Women fought for so long to have the freedom to make their own decisions," but now, every thought in their lives is "boxed in...