Cholesterol processing breaks down, the filtering function fails
For decades, a disease quietly stealing sight from tens of millions went unexplained — doctors could describe its damage but not its origin. Now, researchers from Singapore have traced exfoliation syndrome, the world's leading cause of glaucoma, to a defective gene that disrupts the body's most fundamental cellular chemistry: the processing of cholesterol. The discovery, drawn from the genetic sequencing of more than 20,000 people across three continents, does not yet offer a cure, but it offers something nearly as precious — a direction.
- Exfoliation syndrome silently affects over 70 million people worldwide, causing irreversible blindness through a mechanism that has eluded scientific understanding for decades.
- A defective CYP39A1 gene disrupts cholesterol processing in the eye's epithelial cells, causing abnormal protein deposits to accumulate and destroy the eye's drainage system — raising pressure until vision is gone.
- People with exfoliation syndrome are twice as likely to carry damaging mutations in this single gene, a finding drawn from one of the largest genetic sequencing efforts ever conducted for an eye disease.
- Researchers and clinicians worldwide are now focused on two potential therapeutic pathways: restoring the broken gene's function or blocking the formation of the damaging exfoliative material before it accumulates.
- The study, published in JAMA and praised by experts at Harvard, marks a turning point — not a cure, but the clearest map yet toward one.
Somewhere in the world right now, someone is losing their sight to a disease most people have never heard of. Exfoliation syndrome affects more than 70 million people globally, making it the leading cause of glaucoma and a major driver of irreversible blindness. For decades, doctors knew what happened — abnormal protein accumulated in the front of the eye — but not why. That changed in early 2021 when researchers from Singapore published findings that may finally crack open the question of origin.
The team, drawn from three Singaporean institutions, sequenced the protein-coding genes of more than 20,000 people across 14 countries spanning Asia, Europe, and Africa. Their finding was striking: people with exfoliation syndrome were twice as likely to carry damaging mutations in a single gene called CYP39A1 — an enzyme responsible for processing cholesterol, a molecule fundamental to the health of virtually every cell in the body.
When CYP39A1 is defective, that processing breaks down. Epithelial cells in the front of the eye — which filter blood to produce the fluid nourishing the eye's interior — become particularly vulnerable. Their filtering function deteriorates, allowing abnormal protein deposits to leak into the eye and accumulate where they should not. That buildup damages the eye's drainage system, raises internal pressure, and leads to glaucoma and eventual vision loss.
The findings point toward new therapeutic directions: restoring defective CYP39A1 function or blocking exfoliative material from forming altogether. Senior researchers called it groundbreaking, and outside experts noted it demonstrated the power of studying rare genetic variants to unlock complex disease mechanisms. Published in JAMA, the work now faces its harder test — translating a genetic discovery into treatments that can reach the millions still losing their sight. The mystery is not solved. But for the first time, there is a clear thread to follow.
Somewhere in the world right now, someone is losing their sight to a disease most people have never heard of. Exfoliation syndrome affects more than 70 million people globally, making it the leading cause of glaucoma and a major driver of irreversible blindness. For decades, the disease remained largely a mystery—doctors knew what happened (abnormal protein accumulated in the front of the eye), but not why. That changed in February 2021 when researchers from Singapore published findings that may finally crack open the question of origin.
The team came from three institutions: the Genome Institute of Singapore, the Bioprocessing Technology Institute, and Singapore Eye Research Institute. They sequenced the protein-coding genes of more than 20,000 people across 14 countries spanning Asia, Europe, and Africa. Among those participants were more than 1,200 Singaporeans. What they found was striking: people diagnosed with exfoliation syndrome were twice as likely to carry damaging mutations in a single gene called CYP39A1. The gene encodes an enzyme responsible for processing cholesterol, a molecule present in virtually every cell in the human body.
The discovery reframes how scientists think about the disease. Cholesterol processing is not some exotic metabolic pathway—it is fundamental to cellular health. When the CYP39A1 gene is defective, that processing breaks down. The research pinpointed epithelial cells in the front of the eye as particularly vulnerable. These cells filter blood to produce aqueous humour, the clear fluid that bathes and nourishes the eye's interior structures. When cholesterol processing fails in these cells, their filtering function deteriorates. Abnormal protein material—the exfoliative deposits—begins to leak from the blood into the eye, accumulating where it should not be. That accumulation damages the eye's drainage system and raises internal pressure, leading to glaucoma and eventual vision loss.
For patients and clinicians, the implications are significant. The findings point toward a new therapeutic direction: restoring defective CYP39A1 function or blocking the formation of exfoliative material altogether. Patrick Tan, Executive Director of the Genome Institute of Singapore, called it groundbreaking work that could facilitate future treatment development. Aung Tin, Director of Singapore Eye Research Institute, emphasized the global scale of the problem and the international collaboration that made the discovery possible. Even researchers outside the team recognized the significance. David Friedman, who directs the Glaucoma Service at Massachusetts Eye and Ear Infirmary and holds the Albert and Diane Kaneb Chair in Ophthalmology at Harvard, noted that the study demonstrated the power of examining rare genetic variants to unlock disease mechanisms in complex conditions.
The work was published in the Journal of the American Medical Association, lending it immediate credibility within the medical establishment. But the real test lies ahead. The gene has been identified, the mechanism partially illuminated. Now comes the harder work: translating this knowledge into drugs that can be tested, refined, and eventually delivered to the 70 million people living with exfoliation syndrome. The mystery is not solved. But for the first time, researchers have a clear thread to follow.
Notable Quotes
This is a ground-breaking study that could facilitate future research efforts aimed at restoring defective CYP39A1 function and inhibiting the formation of exfoliation material in the eye as treatments for exfoliation syndrome and glaucoma.— Patrick Tan, Executive Director of Genome Institute of Singapore
This study was notable for involving many centres from many different countries around the world, but led from Singapore. The study findings are very exciting as we found a new pathway for the disease which opens up possibilities for new treatments.— Aung Tin, Director of Singapore Eye Research Institute
The Hearth Conversation Another angle on the story
Why does cholesterol processing matter so much in the eye specifically? Isn't cholesterol everywhere?
It is everywhere, yes. But the eye's epithelial cells have a very specific job—they filter blood to make aqueous humour. When cholesterol processing breaks down there, the filtering function fails. That's when abnormal protein starts leaking into the eye where it shouldn't be.
So the defective gene doesn't cause exfoliation syndrome directly. It causes a breakdown in cholesterol processing, which then causes the protein accumulation.
Exactly. It's a chain. The gene defect disrupts a fundamental cellular process. That disruption compromises the barrier function of these specific cells. The consequence is exfoliation material accumulating and damaging the eye's drainage system.
They studied 20,000 people. That's a massive study. Why was that scale necessary?
Exfoliation syndrome is rare enough that you need a huge sample to find the genetic signal. And they needed people from different populations across three continents to show the mutation wasn't just a regional quirk—it's a real disease mechanism.
What happens now? Do they have a treatment?
Not yet. They have identified the target. The next phase is figuring out how to restore the gene's function or block the protein accumulation. That's years of work ahead.
For someone diagnosed with exfoliation syndrome today, does this discovery change anything?
Not immediately. But it changes what researchers will pursue. Instead of treating symptoms, they now have a pathway to address the root cause. That's the difference between managing a disease and potentially curing it.