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It was 1996, and Masashi Yanagisawa was on the brink of his next discovery.
The Japanese scientist had arrived at the University of Texas Southwestern in Dallas 5 years earlier, setting up his own lab at age 31. After earning his medical degree, he’d gained notoriety as a PhD student when he discovered endothelin, the body’s most potent vasoconstrictor.
Yanagisawa was about to prove this wasn’t a first-timer’s fluke.
His focus was G-protein–coupled receptors (GPCRs), cell surface receptors that respond to a range of molecules and a popular target for drug discovery. The Human Genome Project had just revealed a slew of newly discovered receptors, or “orphan” GPCRs, and identifying an activating molecule could yield a new drug. (That vasoconstrictor endothelin was one such success story, leading to four new drug approvals in the United States over the past quarter century.)
Yanagisawa and his team created 50 cell lines, each expressing one orphan receptor. They applied animal tissue to every line, along with a calcium-sensitive dye. If the cells glowed under the microscope, they had a hit.
“He was basically doing an elaborate fishing expedition,” said Jon Willie, MD, PhD, an associate professor of neurosurgery at Washington University School of Medicine in St. Louis, Missouri, who would later join Yanagisawa’s team.
It wasn’t long before the neon-green fluorescence signaled a match. After isolating the activating molecule, the scientists realized they were dealing with two neuropeptides.
No one had ever seen these proteins before. And no one knew their discovery would set off a decades-long journey that would finally solve a century-old medical mystery — and may even fix one of the biggest health crises of our time, as revealed by research published earlier in 2024. It’s a story of strange coincidences, serendipitous discoveries, and quirky details. Most of all, it’s a fascinating example of how basic science can revolutionize medicine — and how true breakthroughs happen over time and in real time.
But That’s Basic Science for You
Most basic science studies — the early, foundational research that provides the building blocks for science that follows — don’t lead to medical breakthroughs. But some do, often in surprising ways.
Also called curiosity-driven research, basic science aims to fill knowledge gaps to keep science moving, even if the trajectory isn’t always clear.
“The people working on the basic research that led to discoveries that transformed the modern world had no idea at the time,” said Isobel Ronai, PhD, a postdoctoral fellow in life sciences at Harvard University, Cambridge, Massachusetts. “Often, these stories can only be seen in hindsight,” sometimes decades later.
Case in point: For molecular biology techniques — things like DNA sequencing and gene targeting — the lag between basic science and breakthrough is, on average, 23 years. While many of the resulting techniques have received Nobel Prizes, few of the foundational discoveries have been awarded such accolades.
“The scientific glory is more often associated with the downstream applications,” said Ronai. “The importance of basic research can get lost. But it is the foundation for any future application, such as drug development.”
As funding is increasingly funneled toward applied research, basic science can require a certain persistence. What this under-appreciation can obscure is the pathway to discovery — which is often as compelling as the end result, full of unpredictable twists, turns, and even interpersonal intrigue.
And then there’s the fascinating — and definitely complicated — phenomenon of multiple independent discoveries.
As in: What happens when two independent teams discover the same thing at the same time?
Back to Yanagisawa’s Lab ...
... where he and his team learned a few things about those new neuropeptides. Rat brain studies pinpointed the lateral hypothalamus as the peptides’ area of activity — a region often called the brain’s feeding center.
“If you destroy that part of the brain, animals lose appetite,” said Yanagisawa. So these peptides must control feeding, the scientists thought.
Sure enough, injecting the proteins into rat brains led the rodents to start eating.
Satisfied, the team named them “orexin-A” and “orexin-B,” for the Greek word “orexis,” meaning appetite. The brain receptors became “orexin-1” and “orexin-2.” The team prepared to publish its findings in Cell.
But another group beat them to it.
Introducing the ‘Hypocretins’
In early January 1998, a team of Scripps Research Institute scientists, led by J. Gregor Sutcliffe, PhD, released a paper in the journal PNAS. They described a gene encoding for the precursor to two neuropeptides
As the peptides were in the hypothalamus and structurally like secretin (a gut hormone), they called them “hypocretins.” The hypocretin peptides excited neurons in the hypothalamus, and later that year, the scientists discovered that the neurons’ branches extended, tentacle-like, throughout the brain. “Many of the connected areas were involved in sleep-wake control,” said Thomas Kilduff, PhD, who joined the Sutcliffe lab just weeks before the hypocretin discovery. At the time, however, the significance of this finding was not yet clear.
Weeks later, in February 1998, Yanagisawa’s paper came out.
Somehow, two groups, over 1000 miles apart, had stumbled on the same neuropeptides at the same time.
“I first heard about [Yanagisawa’s] paper on NBC Nightly News,” recalls Kilduff. “I was skiing in the mountains, so I had to wait until Monday to get back to the lab to see what the paper was all about.”
He realized that Yanagisawa’s orexin was his lab’s hypocretin, although the study didn’t mention another team’s discovery.
“There may have been accusations. But as far as I know, it’s because [Yanagisawa] didn’t know [about the other paper],” said Willie. “This was not something he produced in 2 months. This was clearly years of work.”
‘Multiple Discovery’ Happens More Often Than You Think
In the mid-20th century, sociologist Robert Merton described the phenomenon of “multiple discovery,” where many scientific discoveries or inventions are made independently at roughly the same time.
“This happens much more frequently in scientific research than people suppose,” said David Pendlebury, head of research analysis at Clarivate’s Institute for Scientific Information, the analytics company’s research arm. (Last year, Pendlebury flagged the hypocretin/orexin discovery for Clarivate’s prestigious Citations Laureates award, an honor that aims to predict, often successfully, who will go on to win the Nobel Prize.)
“People have this idea of the lone researcher making a brilliant discovery,” Pendlebury said. “But more and more, teams find things at the same time.”
While this can — and does — lead to squabbling about who deserves credit, the desire to be first can also be highly motivating, said Mike Schneider, PhD, an assistant professor of philosophy at the University of Missouri, Columbia, who studies the social dynamics of science, potentially leading to faster scientific advancement.
The downside? If two groups produce the same or similar results, but one publishes first, scientific journals tend to reject the second, citing a lack of novelty.
Yet duplicating research is a key step in confirming the validity of a discovery.
That’s why, in 2018, the journal PLOS Biology created a provision for “scooped” scientists, allowing them to submit their paper within 6 months of the first as a complementary finding. Instead of viewing this as redundancy, the editors believe it adds robustness to the research.
‘What the Heck Is This Mouse Doing?’
Even though he’d been scooped, Yanagisawa forged on to the next challenge: Confirming whether orexin regulated feeding.
He began breeding mice missing the orexin gene. His team expected these “knockout” mice to eat less, resulting in a thinner body than other rodents. To the contrary, “they were on average fatter,” said Willie. “They were eating less but weighed more, indicating a slower metabolism.”
The researchers were befuddled. “We were really disappointed, almost desperate about what to do,” said Yanagisawa.
As nocturnal animals eat more at night, he decided they should study the mice after dark. One of his students, Richard Chemelli, MD, bought an infrared video camera from Radio Shack, filming the first 4 hours of the mice’s active period for several nights.
After watching the footage, “Rick called me and said, ‘Let’s get into the lab,’ ” said Willie. “It was four of us on a Saturday looking at these videos, saying, ‘What the heck is this mouse doing?’ ”
While exploring their habitat, the knockout mice would randomly fall over, pop back up after a minute or so, and resume normal activity. This happened over and over — and the scientists were unsure why.
They began monitoring the mice’s brains during these episodes — and made a startling discovery.
The mice weren’t having seizures. They were shifting directly into REM sleep, bypassing the non-REM stage, then quickly toggling back to wake mode.
“That’s when we knew these animals had something akin to narcolepsy,” said Willie.
The team recruited Thomas Scammell, MD, a Harvard neurologist, to investigate whether modafinil — an anti-narcoleptic drug without a clear mechanism — affected orexin neurons.
Two hours after injecting the mice with the medication, the scientists sacrificed them and stained their brains. Remarkably, the number of neurons showing orexin activity had increased ninefold. It seemed modafinil worked by activating the orexin system.
These findings had the potential to crack open the science of narcolepsy, one of the most mysterious sleep disorders.
Unless, of course, another team did it first.
The Mystery of Narcolepsy
Yet another multiple discovery, narcolepsy was first described by two scientists — one in Germany, the other in France — within a short span in the late 1800s.
It would be more than a hundred years before anyone understood the disorder’s cause, even though it affects about 1 in 2000 people.
“Patients were often labeled as lazy and malingerers,” said Kilduff, “since they were sleepy all the time and had this weird motor behavior called cataplexy” or the sudden loss of muscle tone.
In the early 1970s, William Dement, MD, PhD — “the father of sleep medicine” — was searching for a narcoleptic cat to study. He couldn’t find a feline, but several colleagues mentioned dogs with narcolepsy-like symptoms.
Dement, who died in 2020, had found his newest research subjects.
In 1973, he started a narcoleptic dog colony at Stanford University in Palo Alto, California. At first, he focused on poodles and beagles. After discovering their narcolepsy wasn’t genetic, he pivoted to dobermans and labradors. Their narcolepsy was inherited, so he could breed them to populate the colony.
Although human narcolepsy is rarely genetic, it’s otherwise a lot like the version in these dogs.
Both involve daytime sleepiness, “pathological” bouts of REM sleep, and the loss of muscle tone in response to emotions, often positive ones.
The researchers hoped the canines could unlock a treatment for human narcolepsy. They began laying out a path of dog kibble, then injecting the dogs with drugs such as selective serotonin reuptake inhibitors. They wanted to see what might help them stay awake as they excitedly chowed down.
Kilduff also started a molecular genetics program, trying to identify the genetic defect behind canine narcolepsy. But after a parvovirus outbreak, Kilduff resigned from the project, drained from the strain of seeing so many dogs die.
A decade after his departure from the dog colony, his work would dramatically intersect with that of his successor, Emmanuel Mignot, MD, PhD.
“I thought I had closed the narcolepsy chapter in my life forever,” said Kilduff. “Then in 1998, we described this novel neuropeptide, hypocretin, that turned out to be the key to understanding the disorder.”
Narcoleptic Dogs in California, Mutant Mice in Texas
It was modafinil — the same anti-narcoleptic drug Yanagisawa’s team studied — that brought Emmanuel Mignot to the United States. After training as a pharmacologist in France, his home country sent him to Stanford to study the drug, which was discovered by French scientists, as his required military service.
As Kilduff’s replacement at the dog colony, his goal was to figure out how modafinil worked, hoping to attract a US company to develop the drug.
The plan succeeded. Modafinil became Provigil, a billion-dollar narcolepsy drug, and Mignot became “completely fascinated” with the disorder.
“I realized quickly that there was no way we’d find the cause of narcolepsy by finding the mode of action of this drug,” Mignot said. “Most likely, the drug was acting downstream, not at the cause of the disorder.”
To discover the answer, he needed to become a geneticist. And so began his 11-year odyssey to find the cause of canine narcolepsy.
After mapping the dog genome, Mignot set out to find the smallest stretch of chromosome that the narcoleptic animals had in common. “For a very long time, we were stuck with a relatively large region [of DNA],” he recalls. “It was a no man’s land.”
Within that region was the gene for the hypocretin/orexin-2 receptor — the same receptor that Yanagisawa had identified in his first orexin paper. Mignot didn’t immediately pursue that gene as a possibility — even though his students suggested it. Why?
“The decision was simply: Should we lose time to test a possible candidate [gene] among many?” Mignot said.
As Mignot studied dog DNA in California, Yanagisawa was creating mutant mice in Texas. Unbeknownst to either scientist, their work was about to converge.
What Happened Next Is Somewhat Disputed
After diagnosing his mice with narcolepsy, Yanagisawa opted not to share this finding with Mignot, though he knew about Mignot’s interest in the condition. Instead, he asked a colleague to find out how far along Mignot was in his genetics research.
According to Yanagisawa, his colleague didn’t realize how quickly DNA sequencing could happen once a target gene was identified. At a sleep meeting, “he showed Emmanuel all of our raw data. Almost accidentally, he disclosed our findings,” he said. “It was a shock for me.”
Unsure whether he was part of the orexin group, Mignot decided not to reveal that he’d identified the hypocretin/orexin-2 receptor gene as the faulty one in his narcoleptic dogs.
Although he didn’t share this finding, Mignot said he did offer to speak with the lead researcher to see if their findings were the same. If they were, they could jointly submit their articles. But Mignot never heard back.
Meanwhile, back at his lab, Mignot buckled down. While he wasn’t convinced the mouse data proved anything, it did give him the motivation to move faster.
Within weeks, he submitted his findings to Cell, revealing a mutation in the hypocretin/orexin-2 receptor gene as the cause of canine narcolepsy. According to Yanagisawa, the journal’s editor invited him to peer-review the paper, tipping him off to its existence.
“I told him I had a conflict of interest,” said Yanagisawa. “And then we scrambled to finish our manuscript. We wrote up the paper within almost 5 days.”
For a moment, it seemed both papers would be published together in Cell. Instead, on August 6, 1999, Mignot’s study was splashed solo across the journal’s cover.
“At the time, our team was pissed off, but looking back, what else could Emmanuel have done?” said Willie, who was part of Yanagisawa’s team. “The grant he’d been working on for years was at risk. He had it within his power to do the final experiments. Of course he was going to finish.”
Two weeks later, Yanagisawa’s findings followed, also in Cell.
His paper proposed knockout mice as a model for human narcolepsy and orexin as a key regulator of the sleep/wake cycle. With orexin-activated neurons branching into other areas of the brain, the peptide seemed to promote wakefulness by synchronizing several arousal neurotransmitters, such as serotonin, norepinephrine, and histamine.
“If you don’t have orexin, each of those systems can still function, but they’re not as coordinated,” said Willie. “If you have narcolepsy, you’re capable of wakefulness, and you’re capable of sleep. What you can’t do is prevent inappropriately switching between states.”
Together, the two papers painted a clear picture: Narcolepsy was the result of a dysfunction in the hypocretin/orexin system.
After more than a century, the cause of narcolepsy was starting to come into focus.
“This was blockbuster,” said Willie.
By itself, either finding — one in dogs, one in mice — might have been met with skepticism. But in combination, they offered indisputable evidence about narcolepsy’s cause.
The Human Brains in Your Fridge Hold Secrets
Jerome Siegel had been searching for the cause of human narcolepsy for years. A PhD and professor at the University of California, Los Angeles, he had managed to acquire four human narcoleptic brains. As laughter is often the trigger for the sudden shift to REM sleep in humans, he focused on the amygdala, an area linked to emotion.
“I looked in the amygdala and didn’t see anything,” he said. “So the brains stayed in my refrigerator for probably 10 years.”
Then he was invited to review Yanagisawa’s study in Cell. The lightbulb clicked on: Maybe the hypothalamus — not the amygdala — was the area of abnormality. He and his team dug out the decade-old brains.
When they stained the brains, the massive loss of hypocretin-activated neurons was hard to miss: On average, the narcoleptic brains had only about 7000 of the cells versus 70,000 in the average human brain. The scientists also noticed scar tissue in the hypothalamus, indicating that the neurons had at some point died, rather than being absent from birth.
What Siegel didn’t know: Mignot had also acquired a handful of human narcoleptic brains.
Already, he had coauthored a study showing that hypocretin/orexin was undetectable in the cerebrospinal fluid of the majority of the people with narcolepsy his team tested. It seemed clear that the hypocretin/orexin system was flawed — or even broken — in people with the condition.
“It looked like the cause of narcolepsy in humans was indeed this lack of orexin in the brain,” he said. “That was the hypothesis immediately. To me, this is when we established that narcolepsy in humans was due to a lack of orexin. The next thing was to check that the cells were missing.”
Now he could do exactly that.
As expected, Mignot’s team observed a dramatic loss of hypocretin/orexin cells in the narcoleptic brains. They also noticed that a different cell type in the hypothalamus was unaffected. This implied the damage was specific to the hypocretin-activated cells and supported a hunch they already had: That the deficit was the result not of a genetic defect but of an autoimmune attack. (It’s a hypothesis Mignot has spent the last 15 years proving.)
It wasn’t until a gathering in Hawaii, in late August 2000, that the two realized the overlap of their work.
To celebrate his team’s finding, Mignot had invited a group of researchers to Big Island. With his paper scheduled for publication on September 1, he felt comfortable presenting his findings to his guests, which included Siegel.
Until then, “I didn’t know what he had found, and he didn’t know what I had found, which basically was the same thing,” said Siegel.
In yet another strange twist, the two papers were published just weeks apart, simultaneously revealing that human narcoleptics have a depleted supply of the neurons that bind to hypocretin/orexin. The cause of the disorder was at last a certainty.
“Even if I was first, what does it matter? In the end, you need confirmation,” said Mignot. “You need multiple people to make sure that it’s true. It’s good science when things like this happen.”
How All of This Changed Medicine
Since these groundbreaking discoveries, the diagnosis of narcolepsy has become much simpler. Lab tests can now easily measure hypocretin in cerebrospinal fluid, providing a definitive diagnosis.
But the development of narcolepsy treatments has lagged — even though hypocretin/orexin replacement therapy is the obvious answer.
“Almost 25 years have elapsed, and there’s no such therapeutic on the market,” said Kilduff, who now works for SRI International, a non-profit research and development institute.
That’s partly because agonists — drugs that bind to receptors in the brain — are challenging to create, as this requires mimicking the activating molecule’s structure, like copying the grooves of an intricate key.
Antagonists, by comparison, are easier to develop. These act as a gate, blocking access to the receptors. As a result, drugs that promote sleep by thwarting hypocretin/orexin have emerged more quickly, providing a flurry of new options for people with insomnia. The first, suvorexant, was launched in 2014. Two others followed in recent years.
Researchers are hopeful a hypocretin/orexin agonist is on the horizon.
“This is a very hot area of drug development,” said Kilduff. “It’s just a matter of who’s going to get the drug to market first.”
One More Hypocretin/Orexin Surprise — and It Could Be The Biggest
Several years ago, Siegel’s lab received what was supposed to be a healthy human brain — one they could use as a comparison for narcoleptic brains. But researcher Thomas Thannickal, PhD, lead author of the UCLA study linking hypocretin loss to human narcolepsy, noticed something strange: This brain had significantly more hypocretin neurons than average.
Was this due to a seizure? A traumatic death? Siegel called the brain bank to request the donor’s records. He was told they were missing.
Years later, Siegel happened to be visiting the brain bank for another project and found himself in a room adjacent to the medical records. “Nobody was there,” he said, “so I just opened a drawer.”
Shuffling through the brain bank’s files, Siegel found the medical records he’d been told were lost. In the file was a note from the donor, explaining that he was a former heroin addict.
“I almost fell out of my chair,” said Siegel. “I realized this guy’s heroin addiction likely had something to do with his very unusual brain.”
Obviously, opioids affected the orexin system. But how?
“It’s when people are happy that this peptide is released,” said Siegel. “The hypocretin system is not just related to alertness. It’s related to pleasure.”
As Yanagisawa observed early on, hypocretin/orexin does indeed play a role in eating — just not the one he initially thought. The peptides prompted pleasure seeking. So the rodents ate.
In 2018, after acquiring five more brains, Siegel’s group published a study in Translational Medicine showing 54% more detectable hypocretin neurons in the brains of heroin addicts than in those of control individuals.
In 2022, another breakthrough: His team showed that morphine significantly altered the pathways of hypocretin neurons in mice, sending their axons into brain regions associated with addiction. Then, when they removed the mice’s hypocretin neurons and discontinued their daily morphine dose, the rodents showed no symptoms of opioid withdrawal.
This fits the connection with narcolepsy: Among the standard treatments for the condition are amphetamines and other stimulants, which all have addictive potential. Yet, “narcoleptics never abuse these drugs,” Siegel said. “They seem to be uniquely resistant to addiction.”
This could powerfully change the way opioids are administered.
“If you prevent the hypocretin response to opioids, you may be able to prevent opioid addiction,” said Siegel. In other words, blocking the hypocretin system with a drug like those used to treat insomnia may allow patients to experience the pain-relieving benefits of opioids — without the risk for addiction.
His team is currently investigating treatments targeting the hypocretin/orexin system for opioid addiction.
In a study published in July, they found that mice who received suvorexant — the drug for insomnia — didn’t anticipate their daily dose of opioids the way other rodents did. This suggests the medication prevented addiction, without diminishing the pain-relieving effect of opioids.
If it translates to humans, this discovery could potentially save millions of lives.
“I think it’s just us working on this,” said Siegel.
But with hypocretin/orexin, you never know.
A version of this article appeared on Medscape.com.
It was 1996, and Masashi Yanagisawa was on the brink of his next discovery.
The Japanese scientist had arrived at the University of Texas Southwestern in Dallas 5 years earlier, setting up his own lab at age 31. After earning his medical degree, he’d gained notoriety as a PhD student when he discovered endothelin, the body’s most potent vasoconstrictor.
Yanagisawa was about to prove this wasn’t a first-timer’s fluke.
His focus was G-protein–coupled receptors (GPCRs), cell surface receptors that respond to a range of molecules and a popular target for drug discovery. The Human Genome Project had just revealed a slew of newly discovered receptors, or “orphan” GPCRs, and identifying an activating molecule could yield a new drug. (That vasoconstrictor endothelin was one such success story, leading to four new drug approvals in the United States over the past quarter century.)
Yanagisawa and his team created 50 cell lines, each expressing one orphan receptor. They applied animal tissue to every line, along with a calcium-sensitive dye. If the cells glowed under the microscope, they had a hit.
“He was basically doing an elaborate fishing expedition,” said Jon Willie, MD, PhD, an associate professor of neurosurgery at Washington University School of Medicine in St. Louis, Missouri, who would later join Yanagisawa’s team.
It wasn’t long before the neon-green fluorescence signaled a match. After isolating the activating molecule, the scientists realized they were dealing with two neuropeptides.
No one had ever seen these proteins before. And no one knew their discovery would set off a decades-long journey that would finally solve a century-old medical mystery — and may even fix one of the biggest health crises of our time, as revealed by research published earlier in 2024. It’s a story of strange coincidences, serendipitous discoveries, and quirky details. Most of all, it’s a fascinating example of how basic science can revolutionize medicine — and how true breakthroughs happen over time and in real time.
But That’s Basic Science for You
Most basic science studies — the early, foundational research that provides the building blocks for science that follows — don’t lead to medical breakthroughs. But some do, often in surprising ways.
Also called curiosity-driven research, basic science aims to fill knowledge gaps to keep science moving, even if the trajectory isn’t always clear.
“The people working on the basic research that led to discoveries that transformed the modern world had no idea at the time,” said Isobel Ronai, PhD, a postdoctoral fellow in life sciences at Harvard University, Cambridge, Massachusetts. “Often, these stories can only be seen in hindsight,” sometimes decades later.
Case in point: For molecular biology techniques — things like DNA sequencing and gene targeting — the lag between basic science and breakthrough is, on average, 23 years. While many of the resulting techniques have received Nobel Prizes, few of the foundational discoveries have been awarded such accolades.
“The scientific glory is more often associated with the downstream applications,” said Ronai. “The importance of basic research can get lost. But it is the foundation for any future application, such as drug development.”
As funding is increasingly funneled toward applied research, basic science can require a certain persistence. What this under-appreciation can obscure is the pathway to discovery — which is often as compelling as the end result, full of unpredictable twists, turns, and even interpersonal intrigue.
And then there’s the fascinating — and definitely complicated — phenomenon of multiple independent discoveries.
As in: What happens when two independent teams discover the same thing at the same time?
Back to Yanagisawa’s Lab ...
... where he and his team learned a few things about those new neuropeptides. Rat brain studies pinpointed the lateral hypothalamus as the peptides’ area of activity — a region often called the brain’s feeding center.
“If you destroy that part of the brain, animals lose appetite,” said Yanagisawa. So these peptides must control feeding, the scientists thought.
Sure enough, injecting the proteins into rat brains led the rodents to start eating.
Satisfied, the team named them “orexin-A” and “orexin-B,” for the Greek word “orexis,” meaning appetite. The brain receptors became “orexin-1” and “orexin-2.” The team prepared to publish its findings in Cell.
But another group beat them to it.
Introducing the ‘Hypocretins’
In early January 1998, a team of Scripps Research Institute scientists, led by J. Gregor Sutcliffe, PhD, released a paper in the journal PNAS. They described a gene encoding for the precursor to two neuropeptides
As the peptides were in the hypothalamus and structurally like secretin (a gut hormone), they called them “hypocretins.” The hypocretin peptides excited neurons in the hypothalamus, and later that year, the scientists discovered that the neurons’ branches extended, tentacle-like, throughout the brain. “Many of the connected areas were involved in sleep-wake control,” said Thomas Kilduff, PhD, who joined the Sutcliffe lab just weeks before the hypocretin discovery. At the time, however, the significance of this finding was not yet clear.
Weeks later, in February 1998, Yanagisawa’s paper came out.
Somehow, two groups, over 1000 miles apart, had stumbled on the same neuropeptides at the same time.
“I first heard about [Yanagisawa’s] paper on NBC Nightly News,” recalls Kilduff. “I was skiing in the mountains, so I had to wait until Monday to get back to the lab to see what the paper was all about.”
He realized that Yanagisawa’s orexin was his lab’s hypocretin, although the study didn’t mention another team’s discovery.
“There may have been accusations. But as far as I know, it’s because [Yanagisawa] didn’t know [about the other paper],” said Willie. “This was not something he produced in 2 months. This was clearly years of work.”
‘Multiple Discovery’ Happens More Often Than You Think
In the mid-20th century, sociologist Robert Merton described the phenomenon of “multiple discovery,” where many scientific discoveries or inventions are made independently at roughly the same time.
“This happens much more frequently in scientific research than people suppose,” said David Pendlebury, head of research analysis at Clarivate’s Institute for Scientific Information, the analytics company’s research arm. (Last year, Pendlebury flagged the hypocretin/orexin discovery for Clarivate’s prestigious Citations Laureates award, an honor that aims to predict, often successfully, who will go on to win the Nobel Prize.)
“People have this idea of the lone researcher making a brilliant discovery,” Pendlebury said. “But more and more, teams find things at the same time.”
While this can — and does — lead to squabbling about who deserves credit, the desire to be first can also be highly motivating, said Mike Schneider, PhD, an assistant professor of philosophy at the University of Missouri, Columbia, who studies the social dynamics of science, potentially leading to faster scientific advancement.
The downside? If two groups produce the same or similar results, but one publishes first, scientific journals tend to reject the second, citing a lack of novelty.
Yet duplicating research is a key step in confirming the validity of a discovery.
That’s why, in 2018, the journal PLOS Biology created a provision for “scooped” scientists, allowing them to submit their paper within 6 months of the first as a complementary finding. Instead of viewing this as redundancy, the editors believe it adds robustness to the research.
‘What the Heck Is This Mouse Doing?’
Even though he’d been scooped, Yanagisawa forged on to the next challenge: Confirming whether orexin regulated feeding.
He began breeding mice missing the orexin gene. His team expected these “knockout” mice to eat less, resulting in a thinner body than other rodents. To the contrary, “they were on average fatter,” said Willie. “They were eating less but weighed more, indicating a slower metabolism.”
The researchers were befuddled. “We were really disappointed, almost desperate about what to do,” said Yanagisawa.
As nocturnal animals eat more at night, he decided they should study the mice after dark. One of his students, Richard Chemelli, MD, bought an infrared video camera from Radio Shack, filming the first 4 hours of the mice’s active period for several nights.
After watching the footage, “Rick called me and said, ‘Let’s get into the lab,’ ” said Willie. “It was four of us on a Saturday looking at these videos, saying, ‘What the heck is this mouse doing?’ ”
While exploring their habitat, the knockout mice would randomly fall over, pop back up after a minute or so, and resume normal activity. This happened over and over — and the scientists were unsure why.
They began monitoring the mice’s brains during these episodes — and made a startling discovery.
The mice weren’t having seizures. They were shifting directly into REM sleep, bypassing the non-REM stage, then quickly toggling back to wake mode.
“That’s when we knew these animals had something akin to narcolepsy,” said Willie.
The team recruited Thomas Scammell, MD, a Harvard neurologist, to investigate whether modafinil — an anti-narcoleptic drug without a clear mechanism — affected orexin neurons.
Two hours after injecting the mice with the medication, the scientists sacrificed them and stained their brains. Remarkably, the number of neurons showing orexin activity had increased ninefold. It seemed modafinil worked by activating the orexin system.
These findings had the potential to crack open the science of narcolepsy, one of the most mysterious sleep disorders.
Unless, of course, another team did it first.
The Mystery of Narcolepsy
Yet another multiple discovery, narcolepsy was first described by two scientists — one in Germany, the other in France — within a short span in the late 1800s.
It would be more than a hundred years before anyone understood the disorder’s cause, even though it affects about 1 in 2000 people.
“Patients were often labeled as lazy and malingerers,” said Kilduff, “since they were sleepy all the time and had this weird motor behavior called cataplexy” or the sudden loss of muscle tone.
In the early 1970s, William Dement, MD, PhD — “the father of sleep medicine” — was searching for a narcoleptic cat to study. He couldn’t find a feline, but several colleagues mentioned dogs with narcolepsy-like symptoms.
Dement, who died in 2020, had found his newest research subjects.
In 1973, he started a narcoleptic dog colony at Stanford University in Palo Alto, California. At first, he focused on poodles and beagles. After discovering their narcolepsy wasn’t genetic, he pivoted to dobermans and labradors. Their narcolepsy was inherited, so he could breed them to populate the colony.
Although human narcolepsy is rarely genetic, it’s otherwise a lot like the version in these dogs.
Both involve daytime sleepiness, “pathological” bouts of REM sleep, and the loss of muscle tone in response to emotions, often positive ones.
The researchers hoped the canines could unlock a treatment for human narcolepsy. They began laying out a path of dog kibble, then injecting the dogs with drugs such as selective serotonin reuptake inhibitors. They wanted to see what might help them stay awake as they excitedly chowed down.
Kilduff also started a molecular genetics program, trying to identify the genetic defect behind canine narcolepsy. But after a parvovirus outbreak, Kilduff resigned from the project, drained from the strain of seeing so many dogs die.
A decade after his departure from the dog colony, his work would dramatically intersect with that of his successor, Emmanuel Mignot, MD, PhD.
“I thought I had closed the narcolepsy chapter in my life forever,” said Kilduff. “Then in 1998, we described this novel neuropeptide, hypocretin, that turned out to be the key to understanding the disorder.”
Narcoleptic Dogs in California, Mutant Mice in Texas
It was modafinil — the same anti-narcoleptic drug Yanagisawa’s team studied — that brought Emmanuel Mignot to the United States. After training as a pharmacologist in France, his home country sent him to Stanford to study the drug, which was discovered by French scientists, as his required military service.
As Kilduff’s replacement at the dog colony, his goal was to figure out how modafinil worked, hoping to attract a US company to develop the drug.
The plan succeeded. Modafinil became Provigil, a billion-dollar narcolepsy drug, and Mignot became “completely fascinated” with the disorder.
“I realized quickly that there was no way we’d find the cause of narcolepsy by finding the mode of action of this drug,” Mignot said. “Most likely, the drug was acting downstream, not at the cause of the disorder.”
To discover the answer, he needed to become a geneticist. And so began his 11-year odyssey to find the cause of canine narcolepsy.
After mapping the dog genome, Mignot set out to find the smallest stretch of chromosome that the narcoleptic animals had in common. “For a very long time, we were stuck with a relatively large region [of DNA],” he recalls. “It was a no man’s land.”
Within that region was the gene for the hypocretin/orexin-2 receptor — the same receptor that Yanagisawa had identified in his first orexin paper. Mignot didn’t immediately pursue that gene as a possibility — even though his students suggested it. Why?
“The decision was simply: Should we lose time to test a possible candidate [gene] among many?” Mignot said.
As Mignot studied dog DNA in California, Yanagisawa was creating mutant mice in Texas. Unbeknownst to either scientist, their work was about to converge.
What Happened Next Is Somewhat Disputed
After diagnosing his mice with narcolepsy, Yanagisawa opted not to share this finding with Mignot, though he knew about Mignot’s interest in the condition. Instead, he asked a colleague to find out how far along Mignot was in his genetics research.
According to Yanagisawa, his colleague didn’t realize how quickly DNA sequencing could happen once a target gene was identified. At a sleep meeting, “he showed Emmanuel all of our raw data. Almost accidentally, he disclosed our findings,” he said. “It was a shock for me.”
Unsure whether he was part of the orexin group, Mignot decided not to reveal that he’d identified the hypocretin/orexin-2 receptor gene as the faulty one in his narcoleptic dogs.
Although he didn’t share this finding, Mignot said he did offer to speak with the lead researcher to see if their findings were the same. If they were, they could jointly submit their articles. But Mignot never heard back.
Meanwhile, back at his lab, Mignot buckled down. While he wasn’t convinced the mouse data proved anything, it did give him the motivation to move faster.
Within weeks, he submitted his findings to Cell, revealing a mutation in the hypocretin/orexin-2 receptor gene as the cause of canine narcolepsy. According to Yanagisawa, the journal’s editor invited him to peer-review the paper, tipping him off to its existence.
“I told him I had a conflict of interest,” said Yanagisawa. “And then we scrambled to finish our manuscript. We wrote up the paper within almost 5 days.”
For a moment, it seemed both papers would be published together in Cell. Instead, on August 6, 1999, Mignot’s study was splashed solo across the journal’s cover.
“At the time, our team was pissed off, but looking back, what else could Emmanuel have done?” said Willie, who was part of Yanagisawa’s team. “The grant he’d been working on for years was at risk. He had it within his power to do the final experiments. Of course he was going to finish.”
Two weeks later, Yanagisawa’s findings followed, also in Cell.
His paper proposed knockout mice as a model for human narcolepsy and orexin as a key regulator of the sleep/wake cycle. With orexin-activated neurons branching into other areas of the brain, the peptide seemed to promote wakefulness by synchronizing several arousal neurotransmitters, such as serotonin, norepinephrine, and histamine.
“If you don’t have orexin, each of those systems can still function, but they’re not as coordinated,” said Willie. “If you have narcolepsy, you’re capable of wakefulness, and you’re capable of sleep. What you can’t do is prevent inappropriately switching between states.”
Together, the two papers painted a clear picture: Narcolepsy was the result of a dysfunction in the hypocretin/orexin system.
After more than a century, the cause of narcolepsy was starting to come into focus.
“This was blockbuster,” said Willie.
By itself, either finding — one in dogs, one in mice — might have been met with skepticism. But in combination, they offered indisputable evidence about narcolepsy’s cause.
The Human Brains in Your Fridge Hold Secrets
Jerome Siegel had been searching for the cause of human narcolepsy for years. A PhD and professor at the University of California, Los Angeles, he had managed to acquire four human narcoleptic brains. As laughter is often the trigger for the sudden shift to REM sleep in humans, he focused on the amygdala, an area linked to emotion.
“I looked in the amygdala and didn’t see anything,” he said. “So the brains stayed in my refrigerator for probably 10 years.”
Then he was invited to review Yanagisawa’s study in Cell. The lightbulb clicked on: Maybe the hypothalamus — not the amygdala — was the area of abnormality. He and his team dug out the decade-old brains.
When they stained the brains, the massive loss of hypocretin-activated neurons was hard to miss: On average, the narcoleptic brains had only about 7000 of the cells versus 70,000 in the average human brain. The scientists also noticed scar tissue in the hypothalamus, indicating that the neurons had at some point died, rather than being absent from birth.
What Siegel didn’t know: Mignot had also acquired a handful of human narcoleptic brains.
Already, he had coauthored a study showing that hypocretin/orexin was undetectable in the cerebrospinal fluid of the majority of the people with narcolepsy his team tested. It seemed clear that the hypocretin/orexin system was flawed — or even broken — in people with the condition.
“It looked like the cause of narcolepsy in humans was indeed this lack of orexin in the brain,” he said. “That was the hypothesis immediately. To me, this is when we established that narcolepsy in humans was due to a lack of orexin. The next thing was to check that the cells were missing.”
Now he could do exactly that.
As expected, Mignot’s team observed a dramatic loss of hypocretin/orexin cells in the narcoleptic brains. They also noticed that a different cell type in the hypothalamus was unaffected. This implied the damage was specific to the hypocretin-activated cells and supported a hunch they already had: That the deficit was the result not of a genetic defect but of an autoimmune attack. (It’s a hypothesis Mignot has spent the last 15 years proving.)
It wasn’t until a gathering in Hawaii, in late August 2000, that the two realized the overlap of their work.
To celebrate his team’s finding, Mignot had invited a group of researchers to Big Island. With his paper scheduled for publication on September 1, he felt comfortable presenting his findings to his guests, which included Siegel.
Until then, “I didn’t know what he had found, and he didn’t know what I had found, which basically was the same thing,” said Siegel.
In yet another strange twist, the two papers were published just weeks apart, simultaneously revealing that human narcoleptics have a depleted supply of the neurons that bind to hypocretin/orexin. The cause of the disorder was at last a certainty.
“Even if I was first, what does it matter? In the end, you need confirmation,” said Mignot. “You need multiple people to make sure that it’s true. It’s good science when things like this happen.”
How All of This Changed Medicine
Since these groundbreaking discoveries, the diagnosis of narcolepsy has become much simpler. Lab tests can now easily measure hypocretin in cerebrospinal fluid, providing a definitive diagnosis.
But the development of narcolepsy treatments has lagged — even though hypocretin/orexin replacement therapy is the obvious answer.
“Almost 25 years have elapsed, and there’s no such therapeutic on the market,” said Kilduff, who now works for SRI International, a non-profit research and development institute.
That’s partly because agonists — drugs that bind to receptors in the brain — are challenging to create, as this requires mimicking the activating molecule’s structure, like copying the grooves of an intricate key.
Antagonists, by comparison, are easier to develop. These act as a gate, blocking access to the receptors. As a result, drugs that promote sleep by thwarting hypocretin/orexin have emerged more quickly, providing a flurry of new options for people with insomnia. The first, suvorexant, was launched in 2014. Two others followed in recent years.
Researchers are hopeful a hypocretin/orexin agonist is on the horizon.
“This is a very hot area of drug development,” said Kilduff. “It’s just a matter of who’s going to get the drug to market first.”
One More Hypocretin/Orexin Surprise — and It Could Be The Biggest
Several years ago, Siegel’s lab received what was supposed to be a healthy human brain — one they could use as a comparison for narcoleptic brains. But researcher Thomas Thannickal, PhD, lead author of the UCLA study linking hypocretin loss to human narcolepsy, noticed something strange: This brain had significantly more hypocretin neurons than average.
Was this due to a seizure? A traumatic death? Siegel called the brain bank to request the donor’s records. He was told they were missing.
Years later, Siegel happened to be visiting the brain bank for another project and found himself in a room adjacent to the medical records. “Nobody was there,” he said, “so I just opened a drawer.”
Shuffling through the brain bank’s files, Siegel found the medical records he’d been told were lost. In the file was a note from the donor, explaining that he was a former heroin addict.
“I almost fell out of my chair,” said Siegel. “I realized this guy’s heroin addiction likely had something to do with his very unusual brain.”
Obviously, opioids affected the orexin system. But how?
“It’s when people are happy that this peptide is released,” said Siegel. “The hypocretin system is not just related to alertness. It’s related to pleasure.”
As Yanagisawa observed early on, hypocretin/orexin does indeed play a role in eating — just not the one he initially thought. The peptides prompted pleasure seeking. So the rodents ate.
In 2018, after acquiring five more brains, Siegel’s group published a study in Translational Medicine showing 54% more detectable hypocretin neurons in the brains of heroin addicts than in those of control individuals.
In 2022, another breakthrough: His team showed that morphine significantly altered the pathways of hypocretin neurons in mice, sending their axons into brain regions associated with addiction. Then, when they removed the mice’s hypocretin neurons and discontinued their daily morphine dose, the rodents showed no symptoms of opioid withdrawal.
This fits the connection with narcolepsy: Among the standard treatments for the condition are amphetamines and other stimulants, which all have addictive potential. Yet, “narcoleptics never abuse these drugs,” Siegel said. “They seem to be uniquely resistant to addiction.”
This could powerfully change the way opioids are administered.
“If you prevent the hypocretin response to opioids, you may be able to prevent opioid addiction,” said Siegel. In other words, blocking the hypocretin system with a drug like those used to treat insomnia may allow patients to experience the pain-relieving benefits of opioids — without the risk for addiction.
His team is currently investigating treatments targeting the hypocretin/orexin system for opioid addiction.
In a study published in July, they found that mice who received suvorexant — the drug for insomnia — didn’t anticipate their daily dose of opioids the way other rodents did. This suggests the medication prevented addiction, without diminishing the pain-relieving effect of opioids.
If it translates to humans, this discovery could potentially save millions of lives.
“I think it’s just us working on this,” said Siegel.
But with hypocretin/orexin, you never know.
A version of this article appeared on Medscape.com.
It was 1996, and Masashi Yanagisawa was on the brink of his next discovery.
The Japanese scientist had arrived at the University of Texas Southwestern in Dallas 5 years earlier, setting up his own lab at age 31. After earning his medical degree, he’d gained notoriety as a PhD student when he discovered endothelin, the body’s most potent vasoconstrictor.
Yanagisawa was about to prove this wasn’t a first-timer’s fluke.
His focus was G-protein–coupled receptors (GPCRs), cell surface receptors that respond to a range of molecules and a popular target for drug discovery. The Human Genome Project had just revealed a slew of newly discovered receptors, or “orphan” GPCRs, and identifying an activating molecule could yield a new drug. (That vasoconstrictor endothelin was one such success story, leading to four new drug approvals in the United States over the past quarter century.)
Yanagisawa and his team created 50 cell lines, each expressing one orphan receptor. They applied animal tissue to every line, along with a calcium-sensitive dye. If the cells glowed under the microscope, they had a hit.
“He was basically doing an elaborate fishing expedition,” said Jon Willie, MD, PhD, an associate professor of neurosurgery at Washington University School of Medicine in St. Louis, Missouri, who would later join Yanagisawa’s team.
It wasn’t long before the neon-green fluorescence signaled a match. After isolating the activating molecule, the scientists realized they were dealing with two neuropeptides.
No one had ever seen these proteins before. And no one knew their discovery would set off a decades-long journey that would finally solve a century-old medical mystery — and may even fix one of the biggest health crises of our time, as revealed by research published earlier in 2024. It’s a story of strange coincidences, serendipitous discoveries, and quirky details. Most of all, it’s a fascinating example of how basic science can revolutionize medicine — and how true breakthroughs happen over time and in real time.
But That’s Basic Science for You
Most basic science studies — the early, foundational research that provides the building blocks for science that follows — don’t lead to medical breakthroughs. But some do, often in surprising ways.
Also called curiosity-driven research, basic science aims to fill knowledge gaps to keep science moving, even if the trajectory isn’t always clear.
“The people working on the basic research that led to discoveries that transformed the modern world had no idea at the time,” said Isobel Ronai, PhD, a postdoctoral fellow in life sciences at Harvard University, Cambridge, Massachusetts. “Often, these stories can only be seen in hindsight,” sometimes decades later.
Case in point: For molecular biology techniques — things like DNA sequencing and gene targeting — the lag between basic science and breakthrough is, on average, 23 years. While many of the resulting techniques have received Nobel Prizes, few of the foundational discoveries have been awarded such accolades.
“The scientific glory is more often associated with the downstream applications,” said Ronai. “The importance of basic research can get lost. But it is the foundation for any future application, such as drug development.”
As funding is increasingly funneled toward applied research, basic science can require a certain persistence. What this under-appreciation can obscure is the pathway to discovery — which is often as compelling as the end result, full of unpredictable twists, turns, and even interpersonal intrigue.
And then there’s the fascinating — and definitely complicated — phenomenon of multiple independent discoveries.
As in: What happens when two independent teams discover the same thing at the same time?
Back to Yanagisawa’s Lab ...
... where he and his team learned a few things about those new neuropeptides. Rat brain studies pinpointed the lateral hypothalamus as the peptides’ area of activity — a region often called the brain’s feeding center.
“If you destroy that part of the brain, animals lose appetite,” said Yanagisawa. So these peptides must control feeding, the scientists thought.
Sure enough, injecting the proteins into rat brains led the rodents to start eating.
Satisfied, the team named them “orexin-A” and “orexin-B,” for the Greek word “orexis,” meaning appetite. The brain receptors became “orexin-1” and “orexin-2.” The team prepared to publish its findings in Cell.
But another group beat them to it.
Introducing the ‘Hypocretins’
In early January 1998, a team of Scripps Research Institute scientists, led by J. Gregor Sutcliffe, PhD, released a paper in the journal PNAS. They described a gene encoding for the precursor to two neuropeptides
As the peptides were in the hypothalamus and structurally like secretin (a gut hormone), they called them “hypocretins.” The hypocretin peptides excited neurons in the hypothalamus, and later that year, the scientists discovered that the neurons’ branches extended, tentacle-like, throughout the brain. “Many of the connected areas were involved in sleep-wake control,” said Thomas Kilduff, PhD, who joined the Sutcliffe lab just weeks before the hypocretin discovery. At the time, however, the significance of this finding was not yet clear.
Weeks later, in February 1998, Yanagisawa’s paper came out.
Somehow, two groups, over 1000 miles apart, had stumbled on the same neuropeptides at the same time.
“I first heard about [Yanagisawa’s] paper on NBC Nightly News,” recalls Kilduff. “I was skiing in the mountains, so I had to wait until Monday to get back to the lab to see what the paper was all about.”
He realized that Yanagisawa’s orexin was his lab’s hypocretin, although the study didn’t mention another team’s discovery.
“There may have been accusations. But as far as I know, it’s because [Yanagisawa] didn’t know [about the other paper],” said Willie. “This was not something he produced in 2 months. This was clearly years of work.”
‘Multiple Discovery’ Happens More Often Than You Think
In the mid-20th century, sociologist Robert Merton described the phenomenon of “multiple discovery,” where many scientific discoveries or inventions are made independently at roughly the same time.
“This happens much more frequently in scientific research than people suppose,” said David Pendlebury, head of research analysis at Clarivate’s Institute for Scientific Information, the analytics company’s research arm. (Last year, Pendlebury flagged the hypocretin/orexin discovery for Clarivate’s prestigious Citations Laureates award, an honor that aims to predict, often successfully, who will go on to win the Nobel Prize.)
“People have this idea of the lone researcher making a brilliant discovery,” Pendlebury said. “But more and more, teams find things at the same time.”
While this can — and does — lead to squabbling about who deserves credit, the desire to be first can also be highly motivating, said Mike Schneider, PhD, an assistant professor of philosophy at the University of Missouri, Columbia, who studies the social dynamics of science, potentially leading to faster scientific advancement.
The downside? If two groups produce the same or similar results, but one publishes first, scientific journals tend to reject the second, citing a lack of novelty.
Yet duplicating research is a key step in confirming the validity of a discovery.
That’s why, in 2018, the journal PLOS Biology created a provision for “scooped” scientists, allowing them to submit their paper within 6 months of the first as a complementary finding. Instead of viewing this as redundancy, the editors believe it adds robustness to the research.
‘What the Heck Is This Mouse Doing?’
Even though he’d been scooped, Yanagisawa forged on to the next challenge: Confirming whether orexin regulated feeding.
He began breeding mice missing the orexin gene. His team expected these “knockout” mice to eat less, resulting in a thinner body than other rodents. To the contrary, “they were on average fatter,” said Willie. “They were eating less but weighed more, indicating a slower metabolism.”
The researchers were befuddled. “We were really disappointed, almost desperate about what to do,” said Yanagisawa.
As nocturnal animals eat more at night, he decided they should study the mice after dark. One of his students, Richard Chemelli, MD, bought an infrared video camera from Radio Shack, filming the first 4 hours of the mice’s active period for several nights.
After watching the footage, “Rick called me and said, ‘Let’s get into the lab,’ ” said Willie. “It was four of us on a Saturday looking at these videos, saying, ‘What the heck is this mouse doing?’ ”
While exploring their habitat, the knockout mice would randomly fall over, pop back up after a minute or so, and resume normal activity. This happened over and over — and the scientists were unsure why.
They began monitoring the mice’s brains during these episodes — and made a startling discovery.
The mice weren’t having seizures. They were shifting directly into REM sleep, bypassing the non-REM stage, then quickly toggling back to wake mode.
“That’s when we knew these animals had something akin to narcolepsy,” said Willie.
The team recruited Thomas Scammell, MD, a Harvard neurologist, to investigate whether modafinil — an anti-narcoleptic drug without a clear mechanism — affected orexin neurons.
Two hours after injecting the mice with the medication, the scientists sacrificed them and stained their brains. Remarkably, the number of neurons showing orexin activity had increased ninefold. It seemed modafinil worked by activating the orexin system.
These findings had the potential to crack open the science of narcolepsy, one of the most mysterious sleep disorders.
Unless, of course, another team did it first.
The Mystery of Narcolepsy
Yet another multiple discovery, narcolepsy was first described by two scientists — one in Germany, the other in France — within a short span in the late 1800s.
It would be more than a hundred years before anyone understood the disorder’s cause, even though it affects about 1 in 2000 people.
“Patients were often labeled as lazy and malingerers,” said Kilduff, “since they were sleepy all the time and had this weird motor behavior called cataplexy” or the sudden loss of muscle tone.
In the early 1970s, William Dement, MD, PhD — “the father of sleep medicine” — was searching for a narcoleptic cat to study. He couldn’t find a feline, but several colleagues mentioned dogs with narcolepsy-like symptoms.
Dement, who died in 2020, had found his newest research subjects.
In 1973, he started a narcoleptic dog colony at Stanford University in Palo Alto, California. At first, he focused on poodles and beagles. After discovering their narcolepsy wasn’t genetic, he pivoted to dobermans and labradors. Their narcolepsy was inherited, so he could breed them to populate the colony.
Although human narcolepsy is rarely genetic, it’s otherwise a lot like the version in these dogs.
Both involve daytime sleepiness, “pathological” bouts of REM sleep, and the loss of muscle tone in response to emotions, often positive ones.
The researchers hoped the canines could unlock a treatment for human narcolepsy. They began laying out a path of dog kibble, then injecting the dogs with drugs such as selective serotonin reuptake inhibitors. They wanted to see what might help them stay awake as they excitedly chowed down.
Kilduff also started a molecular genetics program, trying to identify the genetic defect behind canine narcolepsy. But after a parvovirus outbreak, Kilduff resigned from the project, drained from the strain of seeing so many dogs die.
A decade after his departure from the dog colony, his work would dramatically intersect with that of his successor, Emmanuel Mignot, MD, PhD.
“I thought I had closed the narcolepsy chapter in my life forever,” said Kilduff. “Then in 1998, we described this novel neuropeptide, hypocretin, that turned out to be the key to understanding the disorder.”
Narcoleptic Dogs in California, Mutant Mice in Texas
It was modafinil — the same anti-narcoleptic drug Yanagisawa’s team studied — that brought Emmanuel Mignot to the United States. After training as a pharmacologist in France, his home country sent him to Stanford to study the drug, which was discovered by French scientists, as his required military service.
As Kilduff’s replacement at the dog colony, his goal was to figure out how modafinil worked, hoping to attract a US company to develop the drug.
The plan succeeded. Modafinil became Provigil, a billion-dollar narcolepsy drug, and Mignot became “completely fascinated” with the disorder.
“I realized quickly that there was no way we’d find the cause of narcolepsy by finding the mode of action of this drug,” Mignot said. “Most likely, the drug was acting downstream, not at the cause of the disorder.”
To discover the answer, he needed to become a geneticist. And so began his 11-year odyssey to find the cause of canine narcolepsy.
After mapping the dog genome, Mignot set out to find the smallest stretch of chromosome that the narcoleptic animals had in common. “For a very long time, we were stuck with a relatively large region [of DNA],” he recalls. “It was a no man’s land.”
Within that region was the gene for the hypocretin/orexin-2 receptor — the same receptor that Yanagisawa had identified in his first orexin paper. Mignot didn’t immediately pursue that gene as a possibility — even though his students suggested it. Why?
“The decision was simply: Should we lose time to test a possible candidate [gene] among many?” Mignot said.
As Mignot studied dog DNA in California, Yanagisawa was creating mutant mice in Texas. Unbeknownst to either scientist, their work was about to converge.
What Happened Next Is Somewhat Disputed
After diagnosing his mice with narcolepsy, Yanagisawa opted not to share this finding with Mignot, though he knew about Mignot’s interest in the condition. Instead, he asked a colleague to find out how far along Mignot was in his genetics research.
According to Yanagisawa, his colleague didn’t realize how quickly DNA sequencing could happen once a target gene was identified. At a sleep meeting, “he showed Emmanuel all of our raw data. Almost accidentally, he disclosed our findings,” he said. “It was a shock for me.”
Unsure whether he was part of the orexin group, Mignot decided not to reveal that he’d identified the hypocretin/orexin-2 receptor gene as the faulty one in his narcoleptic dogs.
Although he didn’t share this finding, Mignot said he did offer to speak with the lead researcher to see if their findings were the same. If they were, they could jointly submit their articles. But Mignot never heard back.
Meanwhile, back at his lab, Mignot buckled down. While he wasn’t convinced the mouse data proved anything, it did give him the motivation to move faster.
Within weeks, he submitted his findings to Cell, revealing a mutation in the hypocretin/orexin-2 receptor gene as the cause of canine narcolepsy. According to Yanagisawa, the journal’s editor invited him to peer-review the paper, tipping him off to its existence.
“I told him I had a conflict of interest,” said Yanagisawa. “And then we scrambled to finish our manuscript. We wrote up the paper within almost 5 days.”
For a moment, it seemed both papers would be published together in Cell. Instead, on August 6, 1999, Mignot’s study was splashed solo across the journal’s cover.
“At the time, our team was pissed off, but looking back, what else could Emmanuel have done?” said Willie, who was part of Yanagisawa’s team. “The grant he’d been working on for years was at risk. He had it within his power to do the final experiments. Of course he was going to finish.”
Two weeks later, Yanagisawa’s findings followed, also in Cell.
His paper proposed knockout mice as a model for human narcolepsy and orexin as a key regulator of the sleep/wake cycle. With orexin-activated neurons branching into other areas of the brain, the peptide seemed to promote wakefulness by synchronizing several arousal neurotransmitters, such as serotonin, norepinephrine, and histamine.
“If you don’t have orexin, each of those systems can still function, but they’re not as coordinated,” said Willie. “If you have narcolepsy, you’re capable of wakefulness, and you’re capable of sleep. What you can’t do is prevent inappropriately switching between states.”
Together, the two papers painted a clear picture: Narcolepsy was the result of a dysfunction in the hypocretin/orexin system.
After more than a century, the cause of narcolepsy was starting to come into focus.
“This was blockbuster,” said Willie.
By itself, either finding — one in dogs, one in mice — might have been met with skepticism. But in combination, they offered indisputable evidence about narcolepsy’s cause.
The Human Brains in Your Fridge Hold Secrets
Jerome Siegel had been searching for the cause of human narcolepsy for years. A PhD and professor at the University of California, Los Angeles, he had managed to acquire four human narcoleptic brains. As laughter is often the trigger for the sudden shift to REM sleep in humans, he focused on the amygdala, an area linked to emotion.
“I looked in the amygdala and didn’t see anything,” he said. “So the brains stayed in my refrigerator for probably 10 years.”
Then he was invited to review Yanagisawa’s study in Cell. The lightbulb clicked on: Maybe the hypothalamus — not the amygdala — was the area of abnormality. He and his team dug out the decade-old brains.
When they stained the brains, the massive loss of hypocretin-activated neurons was hard to miss: On average, the narcoleptic brains had only about 7000 of the cells versus 70,000 in the average human brain. The scientists also noticed scar tissue in the hypothalamus, indicating that the neurons had at some point died, rather than being absent from birth.
What Siegel didn’t know: Mignot had also acquired a handful of human narcoleptic brains.
Already, he had coauthored a study showing that hypocretin/orexin was undetectable in the cerebrospinal fluid of the majority of the people with narcolepsy his team tested. It seemed clear that the hypocretin/orexin system was flawed — or even broken — in people with the condition.
“It looked like the cause of narcolepsy in humans was indeed this lack of orexin in the brain,” he said. “That was the hypothesis immediately. To me, this is when we established that narcolepsy in humans was due to a lack of orexin. The next thing was to check that the cells were missing.”
Now he could do exactly that.
As expected, Mignot’s team observed a dramatic loss of hypocretin/orexin cells in the narcoleptic brains. They also noticed that a different cell type in the hypothalamus was unaffected. This implied the damage was specific to the hypocretin-activated cells and supported a hunch they already had: That the deficit was the result not of a genetic defect but of an autoimmune attack. (It’s a hypothesis Mignot has spent the last 15 years proving.)
It wasn’t until a gathering in Hawaii, in late August 2000, that the two realized the overlap of their work.
To celebrate his team’s finding, Mignot had invited a group of researchers to Big Island. With his paper scheduled for publication on September 1, he felt comfortable presenting his findings to his guests, which included Siegel.
Until then, “I didn’t know what he had found, and he didn’t know what I had found, which basically was the same thing,” said Siegel.
In yet another strange twist, the two papers were published just weeks apart, simultaneously revealing that human narcoleptics have a depleted supply of the neurons that bind to hypocretin/orexin. The cause of the disorder was at last a certainty.
“Even if I was first, what does it matter? In the end, you need confirmation,” said Mignot. “You need multiple people to make sure that it’s true. It’s good science when things like this happen.”
How All of This Changed Medicine
Since these groundbreaking discoveries, the diagnosis of narcolepsy has become much simpler. Lab tests can now easily measure hypocretin in cerebrospinal fluid, providing a definitive diagnosis.
But the development of narcolepsy treatments has lagged — even though hypocretin/orexin replacement therapy is the obvious answer.
“Almost 25 years have elapsed, and there’s no such therapeutic on the market,” said Kilduff, who now works for SRI International, a non-profit research and development institute.
That’s partly because agonists — drugs that bind to receptors in the brain — are challenging to create, as this requires mimicking the activating molecule’s structure, like copying the grooves of an intricate key.
Antagonists, by comparison, are easier to develop. These act as a gate, blocking access to the receptors. As a result, drugs that promote sleep by thwarting hypocretin/orexin have emerged more quickly, providing a flurry of new options for people with insomnia. The first, suvorexant, was launched in 2014. Two others followed in recent years.
Researchers are hopeful a hypocretin/orexin agonist is on the horizon.
“This is a very hot area of drug development,” said Kilduff. “It’s just a matter of who’s going to get the drug to market first.”
One More Hypocretin/Orexin Surprise — and It Could Be The Biggest
Several years ago, Siegel’s lab received what was supposed to be a healthy human brain — one they could use as a comparison for narcoleptic brains. But researcher Thomas Thannickal, PhD, lead author of the UCLA study linking hypocretin loss to human narcolepsy, noticed something strange: This brain had significantly more hypocretin neurons than average.
Was this due to a seizure? A traumatic death? Siegel called the brain bank to request the donor’s records. He was told they were missing.
Years later, Siegel happened to be visiting the brain bank for another project and found himself in a room adjacent to the medical records. “Nobody was there,” he said, “so I just opened a drawer.”
Shuffling through the brain bank’s files, Siegel found the medical records he’d been told were lost. In the file was a note from the donor, explaining that he was a former heroin addict.
“I almost fell out of my chair,” said Siegel. “I realized this guy’s heroin addiction likely had something to do with his very unusual brain.”
Obviously, opioids affected the orexin system. But how?
“It’s when people are happy that this peptide is released,” said Siegel. “The hypocretin system is not just related to alertness. It’s related to pleasure.”
As Yanagisawa observed early on, hypocretin/orexin does indeed play a role in eating — just not the one he initially thought. The peptides prompted pleasure seeking. So the rodents ate.
In 2018, after acquiring five more brains, Siegel’s group published a study in Translational Medicine showing 54% more detectable hypocretin neurons in the brains of heroin addicts than in those of control individuals.
In 2022, another breakthrough: His team showed that morphine significantly altered the pathways of hypocretin neurons in mice, sending their axons into brain regions associated with addiction. Then, when they removed the mice’s hypocretin neurons and discontinued their daily morphine dose, the rodents showed no symptoms of opioid withdrawal.
This fits the connection with narcolepsy: Among the standard treatments for the condition are amphetamines and other stimulants, which all have addictive potential. Yet, “narcoleptics never abuse these drugs,” Siegel said. “They seem to be uniquely resistant to addiction.”
This could powerfully change the way opioids are administered.
“If you prevent the hypocretin response to opioids, you may be able to prevent opioid addiction,” said Siegel. In other words, blocking the hypocretin system with a drug like those used to treat insomnia may allow patients to experience the pain-relieving benefits of opioids — without the risk for addiction.
His team is currently investigating treatments targeting the hypocretin/orexin system for opioid addiction.
In a study published in July, they found that mice who received suvorexant — the drug for insomnia — didn’t anticipate their daily dose of opioids the way other rodents did. This suggests the medication prevented addiction, without diminishing the pain-relieving effect of opioids.
If it translates to humans, this discovery could potentially save millions of lives.
“I think it’s just us working on this,” said Siegel.
But with hypocretin/orexin, you never know.
A version of this article appeared on Medscape.com.