SAN DIEGO — Scientists at the University of California San Diego published a study in Nature on July 1, 2026, revealing the structural mechanisms behind congenital myasthenic syndromes (CMS). This research identified potential drug targets for precision therapies.

Congenital myasthenic syndromes are genetic disorders that impair communication between nerves and muscles. These conditions, which can manifest from birth or early childhood, may cause severe muscle weakness, difficulty walking, impaired breathing, paralysis, or death.

The researchers used cryo-electron microscopy, electrophysiology, and chemical biology to investigate the human acetylcholine receptor. Through these methods, they determined 12 high-resolution structures of disease-causing receptor variants. "We've known for decades which mutations cause these diseases, but not exactly how they damage the receptor or why certain drugs help some patients but not others," said Ryan Hibbs, a professor and chair in the Department of Neurobiology at UC San Diego's School of Biological Sciences.

"By visualizing these receptors at near-atomic resolution, we can now explain how the mutations disrupt their function and begin designing therapies that target the underlying molecular defect," Hibbs said. The study found that "fast-channel" CMS mutations prevent the receptor from opening efficiently when acetylcholine binds. Researchers discovered a drug-binding pocket that can partially restore receptor function using positive allosteric modulators.

In contrast, "slow-channel" CMS mutations cause receptors to remain open excessively, leading to damage at the neuromuscular junction. The study revealed how quinidine and fluoxetine block defective receptors in slow-channel CMS. The team also found that reboxetine, an antidepressant approved in several countries, selectively suppresses abnormal receptor activity responsible for slow-channel disease.

"Rather than studying one mutation at a time, we've uncovered the common mechanisms that explain two entire classes of congenital myasthenic syndromes," said Huanhuan Li, a postdoctoral researcher. "That gives us a framework for understanding newly discovered patient mutations and for designing better therapies in the future." Hibbs added, "Our results show that there probably won't be a single drug that works for every patient. Instead, different mutations respond differently, opening the door to precision medicine approaches for these disorders."

Much of the structural work was conducted in UC San Diego's Goeddel Family Technology Sandbox. Collaborators at Mayo Clinic provided expertise in receptor physiology, and researchers at UC San Francisco synthesized experimental compounds for the study. The research received support from the National Institutes of Health, the Myasthenia Gravis Foundation of America, and the American Heart Association. The authors of the study included Huanhuan Li, Nuriya Mukhtasimova, Jinfeng Teng, Elfie S. Cavalli, Xilin Gu, Jason K. Sello, Steven M. Sine, and Ryan E. Hibbs.

Why It Matters

This study provides detailed structural insights into congenital myasthenic syndromes, a group of genetic disorders leading to severe muscle weakness and potentially life-threatening complications. By identifying the specific mechanisms by which genetic mutations affect the acetylcholine receptor and discovering potential drug targets, the research lays groundwork for the development of targeted therapies. The findings suggest a shift towards precision medicine, where treatments are tailored to specific mutations, potentially offering more effective options for patients with these conditions.