An international series of 10 individuals with ultrarare heterozygous BMAL1 variants present a syndromic neurodevelopmental phenotype (developmental delay, autism, variable sleep issues, seizures, marfanoid features). Functional assays in human cells and Drosophila show both loss- and gain-of-function effects on BMAL1 activity, PER2 expression, circadian rhythms, and memory, supporting BMAL1 disruption as a cause of neurodevelopmental disease.
0:12In a quiet cold, written deep in ourselves. A midnight metronome study... Welcome to Base by Base, the paper cast that brings genomics to you, wherever you are. Thanks for listening, and don't forget to follow and rate us in your podcast app.
0:29Now, take a 2nd and just, you know, imagine the biological clock ticking inside your own cells right now. Because we usually think of this internal rhythm as like just a timekeeper, right? It's the thing telling you when you're supposed to go to sleep and when you're supposed to wake up.
0:45Exactly. your daily schedule. Yeah. But what really happens when the master pacemaker gene just skips a beat. Like, what if that internal clock is actually responsible for physically wiring the brain during early development?
0:58Yeah, it's it is a premise that flips a major assumption in biology completely on its head. Oh definitely. Because today we are exploring how a broken biological clock doesn't just cause a little cellular jet lag, you know?
1:11It can fundamentally alter human neurodevelopment from the ground up. Which is wild to think about. And today we celebrate the work of an international consortium of researchers, including teens from Baylor College Medicine, and the University of Pennsylvania, who have advanced our understanding of how circadian clock genes influence human brain development.
1:31It really is a massive collaborative effort. Yeah, I mean, they managed to connect the dots across continents utilizing global databases like Gene Matcher. Which is, uh, it's just an incredible piece of detective work, but I think to really appreciate what they discovered, you have to understand the basic 24 hour molecular clock humming inside you right now.
1:54Right, the fundamental mechanism. Exactly. this is a transcription translation feedback loop. Inside your cells, you have these 2 key proteins, BMA1 and CLOCK. BMAL one and CLOCK. Got it. Right. And these 2 proteins, heterodimerize, which basically means they physically bind together.
2:11Oh, so like 2 separate pieces clicking together to form one functional unit. Yep, exactly. Okay, let's unpack this. I'm picturing like a factory with a strict 24 hour shift schedule. I like that analogy.
2:23So you have the day shift managers, that's BMAL one and CLOCK. They show up, unlock the doors, and turn on the assembly line to start making the night shift workers. Yes. And in this case, those night shift workers are 2 other families of genes called PER and CRY.
2:40Okay, so the PER and CRY proteins are the night shift. That is a perfect way to visualize it. And, you know, the brilliance of this loop is the built-in shut off valve. Wait, the shutoff valve? Yeah, because as the day goes on, those PER and CRY proteins, the night shift workers, they build up in the cell, and eventually they're just so many of them that they heterodymerize with each other.
3:02Oh they group up. Exactly. They group up, walk into the manager's office and physically block BML1 and CLOC. shut off their own production. Wow. So the night shift workers clock in, fill the factory floor, and eventually just tell the day shift managers to go home.
3:17That is exactly what happens on a molecular level. And then what? Well, then over the next several hours, those night shift workers slowly degrade, they leave. The factory empties out. Right. The block is lifted.
3:28And the day shift managers, BMAL1 and CLSCK, come back to start it all over again. And that whole cycle takes about 24 hours. Yep. Yep. It forms the primary backbone of your daily timekeeping. But wait, if this is just about timing.
3:42Shouldn't a genetic mutation here just make you an extreme night owl, or, I don't know, an extreme early bird? Why are we talking about brain development? You would think so, right? I mean, for decades, that was the assumption.
3:53Really? Yeah. If you look at variants in other clock genes, Uh, like PR2, PR3, or CRY1, they do just cause isolated sleep phase disorders. Just sleep issues. Exactly. You might have advanced sleep phase where your body demands sleep very early in the evening or delayed sleep phase where you can't fall asleep until the early morning.
4:13But their brain function is fine. Completely fine. There are no other major physical or cognitive symptoms. It is purely a shift in your sleep schedules. But the gene we're looking at today, BML1 is clearly doing something different.
4:25It is doing something much more profound. And that is really the core clinical mystery of this deep dive. Because mutations in BMAO one don't just make you a night owl. Not at all. Which brings us to the mission of the study.
4:36The research team set out to track down the true effects of ultra rare variants in the BMAL1 gene. Right, they had to prove it. And to prove their case, they didn't just rely on one method. They attacked the problem from 3 completely different angles, starting with genomic mining.
4:54Yeah, so they turn to massive global databases like Nome, which captures natural genetic variation across the population. And when you look at the data, BMAL1 stands out as a highly constrained gene. Constrained.
5:09Yeah, in genetics, that means the gene is extremely intolerant to loss of function changes. Meaning, if a mutation happens in that specific stretch of code, the human body usually just doesn't tolerate it well.
5:22Exactly. It gets weeded out of the population. So finding anyone living with it is tough. Incredibly rare. So the team used a platform called gene matcher. You can think of it like a matchmaking app for rare diseases.
5:33I've heard of this. Yeah, doctors and researchers around the world upload unidentified genetic profiles of their patients hoping for a match. And what do they find? Through this, they found 10 specific individuals scattered across the globe with ultra rare variants in the BML 1 gene.
5:49Just 10 people in the whole world. Just ten. And 5 of these were de novo mutations. Oh, meaning they were completely spontaneous typos in the genetic code. They weren't inherited from the parents. Exactly.
6:01Finding those 10 people was the crucial 1st step. It proved the mutation exists in that it correlates with severe clinical symptoms. Right, but I guess to prove BML one is the actual culprit driving those symptoms.
6:13You can't just look at patient charts. No, you have to see the broken clock in action, which takes us to the 2nd method. Cell culture. Right. The team had to recreate these exact human mutations inside living cells in a lab.
6:26So they used a human cell culture. Yeah. Specifically, a well-established line of cells known as U2OS, and they used CRISPR gene editing technology to splice the exact variants from those 10 individuals into these lab cells.
6:41This is where the science gets incredibly elegant. They engineered these specific cells to actually glow. Wait, to glow, like visibly. Yeah, they used a per 2 promoter driven Luciferase reporter. A Luciferous reporter.
6:55That sounds like fireflies. That's exactly what it is. Basically, they attach Luciferace, which is a light emitting enzyme found in fireflies. to the per 2 gene. So every time the factory managers, BMAL1, CLOCK, turned on the assembly line to make the per 2 gene, the cell would literally light up.
7:13Exactly. can physically see the clock ticking. So they put all these cells in a dish and gave them a drug called Dexamethazone. What does that do? This drug acts like a starting pistol. It synchronizes all the cells so their internal clocks are on the exact same schedule.
7:28How clever. Yeah. Then over 6 days, the researchers just watched. As the per 2 gene turned on and off, the bioluminescence would rise and fall in a perfect wave. So you could literally watch the rhythm of the 24 hour factory shift.
7:43You could, but, you know, they didn't stop at cells in a Petri dish. Because a cell isn't a brain. Right. To see how a broken clock affects complex things like behavior and memory, you need a living organism.
7:55Which brings us to the 3rd method, animal modeling. The team turned to Drosophila, the common fruit fly. Yes. I always find it amazing that fruit flies are used for this. They have a biological clock, too.
8:06They do, and their clock mechanism is remarkably similar to ours. Flies have an orthologous gene to human BMAL1. Orthologous, meaning like highly homologous, or an equivalent gene in a different species.
8:21Exactly. And in the fruit fly, this equivalent gene is called cycle, or simply psych. Cycle. So by disrupting the fly cycle gene, they can see how the mutation alters sleep wake rhythms, and most importantly, memory formation in a living creature.
8:34Right. That approach allowed them to tie the cellular mechanics back to the real world. And when you look at the clinical phenotype of the 10 human individuals they found, you realize how vital this gene really is.
8:45I mean, the traits are astonishing. They really are. 100% of the individuals with these rare BMAL1 variants has significant developmental delay. All of them? Many of them were diagnosed with autism spectrum disorder.
8:5850% suffered from seizures. Yeah, so we are looking at a distinct neurodevelopmental syndrome. This is a profound rewiring of the brain. And there's also this bizarrely specific physical trait that showed up in several of these patients.
9:13They exhibited what doctors call a marfinoid habitists. Which means very tall stature, unusually long limbs, and joint hypermobility. Yeah, it's a very striking physical finding. It's like finding out the factory timekeeper is somehow also the lead architect for the building's structural scaffolding.
9:31Like, why would a clock gene dictate the shape of your lings? It strange, right? But to understand the mechanism driving all this chaos, we have to go back to the cellular data, the glowing cells. Right, the firefly cells.
9:43What did they shell? Well, when the team tracked the luminescence of the mutated cells over those 6 days, the perfect wave was just gone. completely gone. Yeah, the variants disrupted the normal cycling of PER2 MRNA within that 24 hour period.
9:56So the day shift managers were failing to run the factory. Exactly. The majority of the mutations they tested, like the splice site and frame shift variants, caused a loss of function. Meaning they dampen the magnitude of the clock.
10:08Right. The glowing signal was weak, meaning they decreased the expression of the PER 2 protein. But, and this is key, the researchers found one major exception. There was one specific misence variant. A missense variant is a tiny genetic typo where a single amino acid is swapped out in the protein gene.
10:29Just one typo. Yes. And this specific variant, known as PL201 VR, actually caused a gain a function. A gain of function. Wait, so it made the clock stronger? It hypercharged it. It significantly enhanced the signal magnitude.
10:43It increased the amplitude of the circadian cycling and even advanced the rhythm. Okay, so you have some patients with mutations that severely weaken the clock, and you have this one mutation that supercharges it.
10:53Right. How does a supercharged clock translate to brain development and memory? I would assume a stronger clock means a sharper brain. Well, what's fascinating here is the fly data. To answer that exact question, they took the exact human equivalent mutations and CRISPR them into the fruit flies.
11:09They put the loss of function, broken clock mutation into one group of flies. And they put the gain of function, hypercharge mutation into another group. Then they tested their memory. Which, how exactly do you give a pop quiz to a fruit fly?
11:24It's actually really clever. They use a gold standard behavioral test called appetitive conditioning. They basically tap into the fly's appetite. Makes sense. Food is a good motivator. Always. First, they starve the flies just a little bit.
11:36Then they expose the flies to a very specific odor while simultaneously giving them sugar water. Okay. Later, they expose the flies to a completely different odor, but this time they pair it with plain water.
11:48So a normal, healthy fly quickly learns to associate the 1st odor with a sweet reward. If you give them a choice later, they will walk toward the sugar odor. Right. They form short-term and long-term memories.
12:00It tests their ability to encode and retrieve a memory based on an experience. And what happened to the mutated flies? Did the hypercharged ones, remember the sugar better? Not at all. Really? Yeah, both the gain of function and the loss of function variants absolutely wrecked the flies short and long-term memory.
12:17Both of them. Even the one with the supercharged internal clock. Both of them. The clocks amplitude didn't matter. Any deviation from the perfect natural rhythm impaired their cognition. Wow. I mean, a gain of function through that specific misense variant did improve some basic circadian behavioral rhythms in the flies like when they moved around, but it still severely suppressed their memory.
12:40So sleep and rhythm are not just about resting. They are the periods where the brain hits save on the day's files. Yes. If the clock is running too slow, the filing system crashes. But if the clock is running too fast, the system also crashes.
12:54The normal balanced rhythm is an absolute requirement for proper cognitive function. That is the crucial takeaway from the fly models. Balances everything. Well, here's where it gets really interesting.
13:05Let's look at children with autism spectrum disorder in the general population. Up to 80% of them experience significant sleep difficulties. It's incredibly prevalent. Difficulty falling asleep, trouble staying asleep, incredibly irregular timing.
13:19And historically, in medicine, those sleep issues are treated as a secondary symptom. Like a side effect. Exactly. They are viewed as a frustrating byproduct of the neurodevelopmental disorder itself. Right.
13:31The assumption is that the brain is wired differently. and therefore the sleep is bad. But these findings from the BMAL one variants flip that assumption entirely. Yeah. If we connect this to the bigger picture, it presents a massive potential paradigm shift.
13:46This research forces us to ask, does sleep dysfunction early in life actually cause or worsen the neurodevelopmental signs? That is a huge question for you to consider. I mean, if your biological clock is fundamentally broken from day one.
14:01Does that broken rhythm disrupt the physical wiring of your brain as it grows? That is the working hypothesis here. And if that is true, early and aggressive treatment of sleep in circadian disruption could actively decrease the severity of neurodevelopmental diseases.
14:16That would be amazing. It would. If we can correct circadian behaviors like sleep early enough in a child's development, we might improve the neuro development itself. We might be able to protect the brain's filing system.
14:27But let me push back on this for a second. Sure. Are we absolutely sure it is the rhythm causing the brain issues? Could BML1 just have a completely separate day job in the cell that has nothing to do with timekeeping?
14:41That's fair point. Like maybe it regulates other developmental genes directly, and the sleep disruption is just a coincidence. You have hit on the primary limitation of the study. And to their credit, the researchers are very transparent about the distinction.
14:55Okay, so it is a possibility. Oh, definitely. We actually know that BML1 and its fly equivalent psych do play roles in non-clock mediated cellular morphogenesis. More for genesis, meaning like the physical shaping and building of the cells.
15:08Yes. For example, the fly gene psych is intimately involved in guiding axonal projection. Actual projections. Think of neurons in a growing brain like trees growing roots to connect with other trees. Those roots are the axons.
15:24They have to travel across the brain to form specific circuits. In psych hilt with that. Psych helps direct that traffic. It helps those long fibers grow and find their targets. If that gene is missing or broken early in development, those physical connections in the brain are completely abnormal.
15:41The roots grow in the wrong direction. Ah, so it is structural. It is not just about the 24 hour rhythm. Exactly. BMAO one also modulates the activity of other transcription factors that have absolutely nothing to do with the clock.
15:54So it's multicasking. It is. So, as of right now, it remains unknown if the severe memory impairment we see in these individuals is strictly due to a broken rhythmic clock. It could just be the other stuff.
16:05Right. It is entirely possible that it is just non-rithmic regulation of developmental genes that happen to rely on BMA1 to function. So going back to our analogy, BMAO1 could be the factory timekeeper, blowing the whistle for the shift changes.
16:18Yeah. But it might also be the guy signing the paychecks for the construction crew building the factory walls. That is a brilliant way to frame it. And if BNAL one goes missing, the schedule falls apart, but the walls also collapse.
16:29Exactly. The dual roles of the gene are hard to untangle. And, you know, that structural role might explain why we see those physical musculoskeletal symptoms in the patients. Like the marfinoid habitists with the long limbs.
16:43Precisely. That unique physical growth might be related to BMA one's non-clock functions in developing tissue. So what does this all mean? The core circadian clock gene, BMA1, is essential, not just for daily timekeeping, but for proper human neurodevelopment.
17:00Ultra rare genetic variants that break this clock mechanism cause a distinct neurodevelopmental syndrome, marked by developmental delay, autism, and physical anomalies. What does this mean for the way we view and treat sleep disturbances in early childhood development?
17:16It's definitely something we'll be watching closely in the coming years. This episode was based on an open access article under the CCBY 4.0 license. You can find a direct link to the paper and the license in our episode description.
17:28If you enjoyed this, follow or subscribe in your podcast app and leave a 5 star rating. If you'd like to support our work, use the donation link in the description. Now stay with us for an original track created, especially for this episode, and inspired by the article you've just heard about.
17:43Thanks for listening, and join us next time as we explore more science based by base. In a quiet cold, written deep in ourselves. A midnight metronome, stutters and swells. A tiny change where the timing belongs can bend the day into our face.
18:18Not the hands on the wall But the kids underneath. Turning too fast or too slow in their teeth. If the signal drips The body can't rest. So we listen for rhythm and follow the test. Hold on. Let the light come through.
18:33Set the beach where it's meant to. If the cycle break We can still restore Find the pattern Here the cold We rise when the clock miss fires. oh oh oh oh Yeah Oh, one little whispers. The other replies The locks are a surge in the wake of the tide.
19:10Whoa, hurt to keep speaking in pulses a blow While she runs cooking. And thoughts overflow. Oh, oh, oh, oh, oh, oh, oh, oh In small wing nights, the same story appears. Steps in the dark in the weight of lost years.
19:35Memory flickers Then falls out of tune. But every trace Draws a map to the moon Hold on Let the light come through. Let the light come through. Set the beach where it's meant to move. May the fall, my dream.
19:58But it distorts. Help the restless find their boards. We rise when the clock Miss fires Oh, we rise. When the clock rewired. oh oh oh
