Scientists found the “holy grail” gene that could one day help humans regrow limbs

Scientists studying axolotls, zebrafish, and mice have uncovered a shared set of genes that could someday help researchers develop therapies for regrowing human limbs. The findings, published in the Proceedings of the National Academy of Sciences, point to a possible new direction for regenerative medicine and gene therapy.

"This significant research brought together three labs, working across three organisms to compare regeneration," said Wake Forest Assistant Professor of Biology Josh Currie, whose lab studies the Mexican axolotl salamander. "It showed us that there are universal, unifying genetic programs that are driving regeneration in very different types of organisms, salamanders, zebrafish and mice."

The project also included Duke University plastic surgeon David A. Brown, who studies digit regeneration in mice, and Kenneth D. Poss of the University of Wisconsin-Madison, whose research focuses on fin regeneration in zebrafish.

Shared Regeneration Genes Across Species

Around the world, more than 1 million amputations occur every year due to diabetes-related vascular disease, traumatic injuries, infections, and cancer, according to Global Burden of Disease statistics. Researchers expect that number to climb as populations age and diabetes becomes more common.

For years, scientists have searched for ways to move beyond prosthetic limbs and toward treatments capable of restoring natural movement, sensation, and function. This new study suggests that a group of genes known as SP genes may play a central role in that effort.

Researchers selected axolotls, zebrafish, and mice because each species offers unique insights into regeneration.

Axolotls are famous for their extraordinary ability to regrow entire limbs along with tails, spinal cord tissue, and parts of organs including the heart, brain, lungs, liver, and jaw.

Zebrafish are another powerful regeneration model because they can repeatedly regrow damaged tail fins. They are also capable of repairing the heart, brain, spinal cord, kidneys, retinas, and pancreas.

Mice were included because, like humans, they are mammals. Mice can regenerate the tips of their digits, and humans can sometimes regrow fingertips if the nailbed remains intact after injury, allowing skin, flesh, and bone to regenerate.

Currie said the team discovered that the regenerating epidermis, or skin tissue, in all three species activated two genes called SP6 and SP8. Researchers then began investigating exactly how those genes contribute to regeneration.

Biology Ph.D. student Tim Curtis Jr. participated in the work in Currie's lab, along with undergraduate Elena Singer-Freeman, a Goldwater Scholar and 2025 Wake Forest graduate in biochemistry and molecular biology.

CRISPR Experiments Reveal Key Limb Regrowth Role

The researchers found that SP8 is especially important for limb regeneration in salamanders. Using CRISPR gene-editing technology, Currie's team removed SP8 from the axolotl genome.

Without the gene, axolotls were unable to properly regenerate limb bones. Scientists observed similar problems in mice when SP6 and SP8 were missing from regenerating digits.

Using those findings, Brown's lab designed a viral gene therapy based on a tissue regeneration enhancer previously identified in zebrafish.

The therapy delivered a signaling molecule called FGF8, which is normally activated by SP8. In mice, the treatment encouraged bone regrowth in damaged digits and partially restored some regenerative abilities lost when the SP genes were absent.

Human limbs cannot naturally regenerate the way salamander limbs do, but researchers believe future therapies could potentially imitate some of the biological mechanisms controlled by SP genes.

"We can use this as a kind of proof of principle that we might be able to deliver therapies to substitute for this regenerative style of epidermis in regrowing tissue in humans," Currie explained.

Building Toward Future Human Limb Regeneration

Researchers caution that the work is still at an early stage, and far more studies will be needed before discoveries in mice could translate into therapies for humans. Even so, Currie described the research as an important foundation for future regenerative treatments.

"Scientists are pursuing many solutions for replacing limbs, including bioengineered scaffolds and stem cell therapies," Currie explained. "The gene-therapy approach in this study is a new avenue that can complement and potentially augment what will surely be a multi-disciplinary solution to one day regenerate human limbs."

Currie also emphasized the importance of collaboration between scientists working on very different animals and biological systems.

"Many times, scientists work in their silos: we're just working in axolotl, or we're just working in mouse, or just working in fish," Currie said. "A real standout feature of this research is that we work across all these different organisms. That is really powerful, and it's something that I hope we'll see more of in the field."

Journal Reference:

1. David A. Brown, Katja K. Koll, Erin Brush, Grant Darner, Timothy Curtis, Thomas Dvergsten, Melissa Tran, Colleen Milligan, David W. Wolfson, Trevor J. Gonzalez, Sydney Jeffs, Alyssa Ehrhardt, Rochelle Bitolas, Madeleine Landau, Kendall Reitz, David S. Salven, Leslie A. Slota-Burtt, Isabel Snee, Elena Singer-Freeman, Sayuri Bhatia, Jianhong Ou, Aravind Asokan, Joshua D. Currie, Kenneth D. Poss. Enhancer-directed gene delivery for digit regeneration based on conserved epidermal factors. Proceedings of the National Academy of Sciences, 2026; 123 (17) DOI: 10.1073/pnas.2532804123

Courtesy:

Wake Forest University. "Scientists found the “holy grail” gene that could one day help humans regrow limbs." ScienceDaily. ScienceDaily, 9 May 2026. <www.sciencedaily.com/releases/2026/05/260508003121.htm>.

 

 

 

 

 

New obesity discovery rewrites decades of fat science

For decades, scientists believed they understood one of the body's key fat-burning proteins. Known as hormone-sensitive lipase, or HSL, the enzyme was thought to work mainly as the body's emergency fuel switch, helping release stored fat when energy runs low.

But researchers uncovered something unexpected. HSL was not just working on the surface of fat droplets inside fat cells. It was also operating deep inside the nucleus of those cells, where DNA is stored and important genetic activity is controlled. The discovery revealed an entirely different side to a protein scientists had studied since the 1960s.

The findings, published in Cell Metabolism, helped solve a long-standing mystery in obesity research and opened new directions for understanding diabetes, heart disease, and other metabolic disorders.

Fat Cells Do Far More Than Store Calories

Fat cells, also called adipocytes, are often viewed as passive storage containers for excess calories. In reality, they are highly active cells that help regulate the body's entire energy system.

Inside adipocytes, fat is stored in structures called lipid droplets. When the body needs fuel between meals or during fasting, hormones such as adrenaline trigger the release of that stored energy. HSL plays a central role in this process by breaking down triglycerides into fatty acids that other organs can use for fuel.

Scientists long assumed that removing HSL would prevent fat breakdown and lead to obesity. Surprisingly, that is not what happened.

Studies in both mice and people with mutations in the HSL gene showed the opposite effect. Instead of accumulating extra fat, they developed lipodystrophy, a rare condition in which the body loses healthy fat tissue.

That contradiction puzzled researchers for years.

Obesity and Dangerous Fat Loss Share Similar Problems

Although obesity and lipodystrophy seem completely different, they can produce many of the same health complications.

In obesity, fat tissue becomes enlarged and dysfunctional. In lipodystrophy, the body lacks enough properly functioning fat tissue. In both cases, adipocytes fail to regulate energy normally, which can contribute to insulin resistance, type 2 diabetes, fatty liver disease, inflammation, and cardiovascular problems.

This overlap suggested that healthy fat tissue is not simply about how much fat the body carries. The quality and function of fat cells may be just as important.

Researchers at the Institute of Cardiovascular and Metabolic Diseases (I2MC) at the University of Toulouse wanted to understand why the loss of HSL caused fat tissue to break down instead of build up. What they found changed the scientific picture of fat metabolism.

Scientists Discover HSL Inside the Cell Nucleus

The research team, led by Dominique Langin, discovered that HSL was located in an unexpected place inside adipocytes: the nucleus.

The nucleus acts as the cell's control center. It contains DNA and regulates which genes are switched on or off. Proteins found in the nucleus often help control cell growth, repair, metabolism, and communication.

"In the nucleus of adipocytes, HSL is able to associate with many other proteins and take part in a program that maintains an optimal amount of adipose tissue and keeps adipocytes 'healthy'," explained Jérémy Dufau, co-author of the study.

Researchers found that nuclear HSL appears to help regulate important cellular systems, including mitochondrial activity and the extracellular matrix, which provides structural support for tissues.

Mitochondria are often called the power plants of cells because they generate energy. The extracellular matrix helps maintain the shape and integrity of tissues. Problems in either system have been linked to obesity, inflammation, and metabolic disease.

A Protein With Two Very Different Jobs

The study showed that HSL behaves differently depending on where it is located inside the cell.

On lipid droplets, HSL acts as an enzyme that helps release stored fat during fasting or exercise. In the nucleus, however, it appears to work more like a regulator that helps maintain healthy adipose tissue.

Researchers also discovered that the amount of HSL inside the nucleus changes in response to the body's metabolic state.

During fasting, adrenaline activates HSL and pushes it out of the nucleus so it can help mobilize fat stores. In obese mice fed a high-fat diet, nuclear HSL levels increased.

The protein's movement appears to be controlled by signaling pathways involving TGF-β and SMAD3, molecules already known to influence inflammation, tissue remodeling, and metabolic disease.

Scientists also found evidence that nuclear HSL interacts with proteins involved in gene expression and RNA processing, suggesting it may directly influence how fat cells function at a genetic level.

Why the Discovery Matters

The findings helped explain why complete HSL deficiency causes lipodystrophy instead of obesity. Without HSL in the nucleus, fat cells may lose their ability to stay healthy and properly maintain adipose tissue.

"HSL has been known since the 1960s as a fat-mobilizing enzyme. But we now know that it also plays an essential role in the nucleus of adipocytes, where it helps maintain healthy adipose tissue," Langin said.

The discovery may also help researchers better understand why some obesity treatments succeed while others fail. Many current therapies focus mainly on reducing fat mass. But the study suggests preserving healthy fat tissue function could be equally important.

Scientists are increasingly recognizing that adipose tissue acts as a complex endocrine organ that communicates with the brain, liver, muscles, and immune system through hormones and signaling molecules. Dysfunctional fat tissue can disrupt the body far beyond weight gain alone.

Obesity Remains a Global Health Challenge

The research arrives as obesity rates continue to rise worldwide. According to global estimates, billions of people are now overweight or obese, increasing the risk of diabetes, heart disease, stroke, sleep apnea, and some cancers.

Researchers hope that understanding how proteins like HSL regulate fat cell health could eventually lead to more targeted therapies for metabolic disease.

Instead of simply trying to eliminate fat, future treatments may focus on restoring the normal function of adipocytes and protecting the biological systems that keep fat tissue healthy in the first place.

Journal Reference:

1. Jérémy Dufau, Emeline Recazens, Laura Bottin, Camille Bergoglio, Aline Mairal, Karima Chaoui, Marie-Adeline Marques, Veronica Jimenez, Miquel García, Tongtong Wang, Henrik Laurell, Jason S. Iacovoni, Remy Flores-Flores, Pierre-Damien Denechaud, Khalil Acheikh Ibn Oumar, Ez-Zoubir Amri, Catherine Postic, Jean-Paul Concordet, Pierre Gourdy, Niklas Mejhert, Mikael Rydén, Odile Burlet-Schiltz, Fatima Bosch, Christian Wolfrum, Etienne Mouisel, Genevieve Tavernier, Dominique Langin. Nuclear hormone-sensitive lipase regulates adipose tissue mass and adipocyte metabolism. Cell Metabolism, 2025; 37 (11): 2250 DOI: 10.1016/j.cmet.2025.09.014

Courtesy:

Université de Toulouse. "New obesity discovery rewrites decades of fat science." ScienceDaily. ScienceDaily, 8 May 2026. <www.sciencedaily.com/releases/2026/05/260508171123.htm>.