Cool Stuff Last Week: The thantotranscriptome, sticky chameleon spit, and a window into the second brain

1. Your genes keep working even after you die

Logophiles rejoice: you can now add “thantotranscriptome” to your vocabulary. Thantotranscriptome is defined as “genes actively expressed after organismal death.” Yep, there are genes in your body that will specifically activate after your death. All throughout life, our genes are expressed in tightly choreographed patterns. Precise gene expression patterns lay out how a child should develop, look, and grow, even before birth. All the way through adulthood, genes are responsible for our every bodily function. Now, it appears that even when we die and our cells shut down, genes continue to be expressed up to two days later.

In their preprint article (which has been submitted for peer review but has not yet been accepted), the researchers said they expected the death of a complex organism to be somewhat like a car running out of gas. “For a short time,” they remarked, “engine pistons will move up and down and spark plugs will spark – but eventually the car will grind to a halt and die.” However, this is not at all what they found. Instead of genes slowly shutting off, new genes started being turned on, even a day or two after death. “In our car analogy, one would not expect window wipers to suddenly turn on and the horn to honk several days after running out of gas.” Yet apparently they do. Genes involved in transporting molecules around the cell are activated shortly after death. Various cancer-related genes turn on between 1 and 48 hours postmortem. Perhaps most surprisingly, developmental genes that had not been activated since before birth were found to be activated, some even 96 hours after death.

All of these studies were carried out in mice and zebrafish, but the researchers expect the findings to be relevant to humans as well. While they were primarily motivated by curiosity – no one really knows how our bodies shut down after death – this research could be applied to forensic science to help pin down a more accurate time of death, even down to the half-hour.   

2. Chameleon spit is sticky

In a groundbreaking Nature Physics paper published earlier this week, scientists found that chameleon spit is sticky. Okay, but if you thought you already knew this, you’re wrong. Shockingly, until now, no one actually thought to check whether chameleon spit is sticky. Chameleons’ tongues can reach two body lengths away and capture prey up to a third of their own body weight. And they do this so fast that their tongues require built-in catapults because muscle alone physically cannot accelerate that quickly. This speed and power belie an ability to successfully grab on to prey (try shooting your hand out toward a glass as fast as you possibly can and see if you grab it successfully or just knock it off the table).

Scientists have long speculated that roughness, suction, or stickiness may help the chameleon’s tongue grab its lunch and hang on, but someone finally opened up a chameleon’s mouth and discovered, yep, chameleon spit is a whopping 400 times stickier than human saliva. The scientists who conducted the study also found that the adhesive powers of the tongue were given a boost during the retraction phase, meaning that when the chameleon pulls its tongue back, the spit on the end of its tongue is more adhesive than when the prey finally makes it to the chameleon’s mouth. This “sticky spit” mechanism may be used by other animals that use their tongues to grab prey as well, and it could even inspire engineers to develop new kinds of glue!

3. A window into the second brain

If you had to take a wild guess as to how many brain the average person has, you might say one. Or slightly less than one, depending on your level of cynicism. Actually, though, there are so many neurons in your gut that some biologists refer to it as the second brain. These neurons are the reason you get butterflies in your stomach when you see someone cute, or a sinking feeling when you see someone you’d rather avoid. Your gut also produces 90% of your body’s serotonin, a neurotransmitter that helps regulate mood and is often a target for treating depression. In fact, the nerves in the gut probably play a big role in all kinds of disorders, from GI problems to diabetes to mood disorders, but relatively little is known about them.

A team led by Xiling Shen implanted a transparent window into the abdomens of mice and integrated a graphene electrode to measure the electrical signals. The scientists were able to watch and record as neurons in the gut fired away. The setup could be very important for gut biologists in the future, allowing them to manipulate conditions and observe how gut neurons respond.



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