Who's going to tell them about prions?
this post was submitted on 02 Jul 2025
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They're like an origami figure folded wrongly that causes any properly folded origami figures to become misfolded when it comes in contact with them.
Fucking prions. When I first learned about them in high school they really made me freak out. They are like the new game+ final boss of things fucking with things. Like how can they even infect other things, fucking mangled and misfolded looking ass, fuck them!
Definitely don’t think about the overpopulation of deer, the spread of CWD, the fact that deer are commonly found in corn fields, the US loves corn, and the plants can take up prions from the soil.
That interspecies barrier seems like it’s the only thing between us and a huge disaster.
Im glad barriers never break and we will be fine forever.
One of the theories how organisms switched from RNA to DNA is due to viruses. Viruses have a pretty wild range of their genetic diversity. Single strand DNA, double strand DNA, positive sense single strand RNA, negative sense single strand RNA, double strand RNA. We’ve also probably got viruses as a permanent part of our genome from some ancestor species.
I think they’re pretty cool. Also, they do respond to outside stimuli, otherwise they’d be completely inert.
We’ve also probably got viruses as a permanent part of our genome from some ancestor species.
We definitely have viruses as a permanent part of our genome. A type of herpes virus is present in the DNA of all living things descended from bony fishes
Mammals wouldn't have a chorioallantoic placenta at all if not for a virus integrated into our genome. Mapping when in evolution the genes responsible for placental development first appeared was my first participation in scientific research, so I love this topic.
Can you send the paper? Please. 🥺
explain please
Happily! Basically, the true placenta we mammals (Eutheria) have is what allows such a long gestation period. Unlike our closely related marsupials, that quickly deplete their resources and must give birth, our placenta allows for a continuous exchange of nutrients. This involves a quite complicated process of embryonic tissue invading the uterine wall, so you can imagine the kind of immunological regulation that must be taking place for that to work.
So you'd assume we have several genes highly specific to our placenta that appear when we Eutherians first appeared... right? No! Turns out the vast majority already existed in jawed vertebrates (our common ancestor with sharks), then quite a lot show up in bony fish (our common ancestor with most things you call fish), and just one shows up in Tetrapoda (our common ancestor with amphibians).
So most of the framework for developing an organ such as the placenta already existed for millions of years, so what exactly was missing before it could finally show up in evolutionary history? The two genes that are absolutely required for this whole crazy "let's invade the mother's uterine wall tissue but NOT trigger her immune system" part: CSF2 and a group of closely related genes called syncitins.
Syncitins are the star here, because they're actually a gene that came from ancient retroviruses. In the virus, they were expressed in the envelope and controlled the fusion between the viral particle and the host cell. These viruses got integrated into our genome, and this "fusion with the host cell" mechanism became extremely useful and crucial for the placenta, basically allowing it to exist.
That is nuts and a really good explaination, thank you!
Thanks for talking about that, that's really cool!
So, in other words, viruses did parts of the work of evolution by inventing the CSF2 and syncitin genes?
And that regulates the immune system to not respond to foreign tissue?
Basically, yes. Viruses came up with the syncitins to fuse with host cells, then when they infected us and integrated their genome we had the code for making these proteins... and turns out "invading tissue" was a really useful tool for the embryo.
i am wondering (in case you know), what activates these genes?
i.e., i'd like to understand how gene regulation works in general. what causes genes to become active all of a sudden?
i.e., why does the genes allow embryos to live inside the mother, but not allow other intruders to live inside the human?
That's a fantastic question... which is exactly what I'm pursuing in my master's degree right now :). The goal will be to have a full metabolic map showing all the involved genes and how they interact, when they're triggered (and by which signaling pathways) and how it all comes together for placental development.
I vaguely remember something about organelles inside a cell used to be seperate entities too
Yeah but they didn't use to be viruses, they used to be bacteria.
And they didn't integrate into human genome. They're just another foreign body that lives inside human cells, but they have their own genome still.
Mitochondria, for sure. They even still have their own DNA separate from your actual human DNA.
Also, they do respond to outside stimuli, otherwise they’d be completely inert.
Do they actually respond? Or is it the external stimuli responding to them?
They respond because they have to do things like inject the genetic material into the organism once it latches on to whatever on the cell surface. That doesn’t occur in the host, it occurs in the virus.
It’s been a while since I took virology, but I feel pretty confident that something occurs in the virus due to an external stimulus.
Viruses are nanomachines.
Change my mind.
they're not so much machines and more blueprints that makes the machine that's already there do different stuff.
Frankly, all life and life-adjacent things on this planet are either nanomachines or scalable nanomachines.
One might call those scaled up nanomachines "machines".
Never heard of it. Did you mean to say gigananomachines?
Pretty sure those "horrible little scalawags" play some pretty crucial roles in the human microbiome...
In the same way that the mafia plays a crucial role in the Italian ~~mafia~~ government. They’re still a bunch of dicks, even if they’re working for us. Move ‘em 2 millimeters in the wrong direction and you’ll have a bad time
I'm actually interested, is this true?
When bacteria were first discovered, people found them in the gut and thought "oh, that's horrible. bacteria cause diseases, so we must get rid of them." it was only found out much later that bacteria in the gut can improve health on average.
the same is true for many other categories of living beings, such as insects (worms), fungi; and now my question is whether it could be the same for viruses?
Some perform tasks, but they largely just take up space, and that’s a good thing. Your body’s full of materials that malignantly pathogenic bacteria would love to get their hands on. Bacteria that are largely incapable of doing anything to us take up space that would otherwise be occupied. You’d likely prefer an old squatter living in your walls, rather than a crackhead. You’d probably choose an electrician, but that’s life. Better they’re largely benign than overtly and desperately malicious.
You factually do have a viral balance in your internal ecosystem. Bacteriophages cull populations, and some viruses hyper-specialize in attacking cancer. There are more examples, but I can’t immediately recall
thank you, that makes sense to me.
i'm interested in actually understanding what functions what elements of the gut microbiome perform. but i guess that's a highly complicated topic, so i expect no quick answers
You’re asking a question without a complete answer, as it’s a complex system in active research, but truthfully, I only know of a couple offhandedly. Some strains of lactobacillus occupy space largely benignly, and some E. coli produce vitamin k. But mostly, they’re just eating and multiplying. Hit up Wikipedia for an abundance of specifics.
Move ‘em 2 millimeters in the wrong direction and you’ll have a bad time
Are you referring to getting, I dunno, yogurt in places outside the digestive tract?
My understanding was that gut bacteria play a pretty crucial (beneficial) role in overall health, not to mention the whole gut-brain stuff.
Take some of those same bacteria and set them directly against the intestinal lining without any of the delicious mucus in the way and you’ll have a slightly unpleasant time. And I’m being literal. It’ll be aggravating, and deleterious to your long term health, but usually not immediately life threatening. They’re absolutely beneficial, but they’re in it for themselves. They’re not beneficent, they just are, which was all the point I intended to make.
“Go back to where you were born, go back to nothing, homunculus”