Hi and welcome back! Every human who is ever born will die. Hopefully, that’ll happen after we’ve lived as long and as full a life as we desire. That means that aging is a natural part of life — something everyone goes through if they live long enough. Hey, it beats the alternative! But scientists have made a groundbreaking discovery: mouse embryos somehow reset their own biological clocks. It’s an incredible find, one that could change the entire aging game for humans one day. Today, Lord Snow Presides over something that might not be as set in stone as death and taxes.
(This week’s 1st-Century Friday topic can be found here.)
Biological Clocks, Generally.
We have a lot of biological clocks. They’re processes in our bodies that tie us to the natural world somehow.
One biological clock, circadian rhythm, controls our waking and sleeping cycles. A uterus’ ability to produce a healthy baby famously declines — markedly so, in fact — according to another biological clock.
But for this story, we’re zeroing in on one particular type of biological clock: the one that controls how every person ages and how that aging shall proceed. That link lists about a dozen different markers in organisms’ cells that control how they age.
The marker most people have heard of involves telomere attrition. Telomeres are the “endcaps” of each of an organism’s chromosomes. They’re nonfunctional genetic code that repeats itself many times. As cells divide over and over again, those endcaps slowly erode away to nothing. When they finally fully erode away, the cell stops dividing. (That “endcap” link offers some interesting explanations for why cells might have evolved to do this. It may confer a serious benefit.)
So yes, all organisms are doomed to eventually end up with a shortage of cells that can divide anymore — and that’s when organisms begin to deteriorate. Diseases that affect how quickly an organism ages only make those telomeres erode faster. Once they’re gone, they’re gone.
As you might guess from that link about markers, scientists can tell the biological age of a cell by examining it. And in a recent study, scientists studying those markers found something interesting.
Biological Clocks — Resetting.
Usually, biological clocks don’t reset. They can’t. That’s the whole point of having biological clocks in the first place. They can be made to age faster through environmental damage (like oxidative stress — which is why you see health foods advertising their ability to fight “free radicals” in your body). But they can’t be reset. What has grown elderly cannot become youthful again.
However, embryos throw the rules out the window.
And they do it for a reason.
In this study that came out a week or so ago, scientists sought to answer an interesting question:
When embryos are conceived, why don’t they bear the same biological clocks of their parents’ eggs and sperm?
As one of the researchers, Yukiko Yamashita, said, “When you are born, you don’t inherit your parents’ age. For some reason, you are at zero.”
Why, though? And how do embryos get to zero? It’s not that eggs and sperm are simply ageless. They’re not. We figured that out a long time ago, according to the study writeup. Both eggs and sperm show signs of aging. So embryos don’t start out at ground zero.
The answer appears to be that they simply reset their biological clocks after conception.
How Biological Clocks Get Reset.
These scientists checked out epigenetic changes, which are DNA tags that indicate damage.
(Channeling my inner ChubbyEmu! Epi: meaning over and above. Genetic: meaning the genome, genes, and heredity. Epigenetics, then, is the study of inherited changes in gene function that sit atop the actual DNA sequencing. Epigenetic tags can tell us what a gene is doing, like how it’s expressed, but these tags don’t change the actual information contained within the gene.)
Then scientists compared the biological ages of these embryos with their chronological age. Apparently, the scientists drew upon machine learning to figure out these relationships — what an incredible way to use new technology!
They discovered that very early in development, like a week or 10 days after fertilization, the embryos’ cells suddenly dropped in biological age according to various markers.
Yes. Those cells had rejuvenated themselves. Then, after that “rejuvenation event,” they began to age normally again.
Interestingly, the full writeup tells us that even in the worst imaginable environments, the embryos chugged right along:
Even under artificial culture conditions, at the level of oxygen above physiological, and with the number of passages well beyond physiological (which may lead to the accumulation of deleterious mutations), either no or very little increase in epigenetic age was observed. These findings support the notion that cells corresponding to the early stages of embryogenesis essentially do not age.
I strongly suspect that happy background buzz I’m hearing right now is the effervescent joy of researchers who’ve found something very, very exciting — but are trying very hard to phrase it in clinical-science-speak. You can just about hear the SQUEEEEEEEEEEEE between the lines here.
More Questions Than Answers.
This was a really preliminary study done on mouse embryos. For what are likely obvious reasons, researchers can’t do tons of research on human embryos. So it’s hard to say exactly where humans fall along this rejuvenation path. However, what researchers could study, they did — and they found that humans do seem to undergo a similar rejuvenation event in early development.
Nor does this study figure out exactly how rejuvenation happens. What mechanism is doing it? How? Where is it? What genes control it? Is it something every organism does? And what happens when things go hideously wrong in development and an embryo doesn’t ever rejuvenate when it’s supposed to? Most importantly, how can we draw upon this knowledge to help people suffering from diseases like cancer and progeria?
But that’s the lovely thing about science. As Dara Ó Briain has said:
Science knows it doesn’t know everything; otherwise, it’d stop. But just because science doesn’t know everything doesn’t mean you can fill in the gaps with whatever fairy tale most appeals to you.
That second bit’s of extreme importance to the process of asking questions. We’ve got to be able to find real answers for our questions — not ones that reinforce indoctrination at the cost of intellectual integrity.
Whatever answers we find, they’ll expand our knowledge of the real world — at a time when reality is becoming more and more important to us as a species.
Today, Lord Snow Presides over a blossoming of questions in response to an age-old question.
NEXT UP: Why pastors reach for sermon swiping and prep services (and also why Christians think they do). See you tomorrow!
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1st-Century Friday Topic:
Wiki writeup. Livy lived, roughly, from about 64-59 BCE to 12-17 CE.
Relevant writing from Project Gutenberg. We’re looking at his end-of-life work in particular to see what he had to say about Jerusalem in the early years of the 1st century.
As always, homework is not required. This announcement is provided only for those who want to read the source material ahead of time. (Back to the post!)
About Lord Snow Presides (LSP)
Lord Snow Presides is our off-topic weekly chat series. Lord Snow was my very sweet white cat. He actually knew quite a bit. Though he’s passed on, he now presides over a suggested topic for the day. Of course, please feel free to chime in with anything on your mind: there’s no official topic on these days. I’m just starting us off with something, but consider the sky the limit here. We especially welcome pet pictures! So what’s on your mind today?
I liked this story about Chinese mountain cats, myself.