A new primate model provides significant opportunities for future gene therapies
Why are some people unable to hear from birth, even though their inner ear appears intact? One possible cause lies in the so-called OTOF gene. It plays a central role in transmitting sound signals from the hair cells to the auditory nerve. Without this function, acoustic information does not reach the brain. Researchers from the German Primate Center – Leibniz Institute for Primate Research, the University Medical Center Göttingen, and the Max Planck Institute for Multidisciplinary Sciences have now, for the first time, generated marmosets in which this gene has been knocked out precisely. The animals are healthy and develop normally, but are deaf from birth. This provides the first primate model that realistically replicates key characteristics of human deafness (Nature Communications).
Hearing loss is one of the most common congenital sensory disorders in humans. A major cause is a defect in the OTOF gene. This gene ensures that the protein otoferlin is produced in the inner ear. This protein is necessary for sound signals to travel from the hair cells to the auditory nerve. Without it, the ear still functions externally, but the signals do not reach the brain.
Genetically modified marmosets
The Göttingen research team used the CRISPR/Cas9 gene-editing tool to modify precisely the OTOF gene in fertilized marmoset eggs, rendering it non-functional in the resulting offspring. The genetically modified embryos were then implanted into a surrogate mother. The animals that were born developed normally, but they were deaf from birth. Hearing tests using electrophysiological methods, similar to an EEG, confirmed deafness, as is also observed in patients with an OTOF gene defect. The absence of otoferlin protein in the inner hair cells further confirmed the genetic knockout.
A crucial step toward new therapies
“With the OTOF-knockout marmosets, we now have, for the first time, a primate model that realistically replicates human OTOF-related hearing loss,” says Tobias Moser, Director of the Institute of Auditory Neuroscience at the University Medical Center Göttingen. “This gives us a crucial tool for developing new therapies in a more targeted and safer manner, while also considering their long-term effects.”
The new model bridges an important gap between mouse models, cell culture systems, and clinical application. It enables studies under conditions that more closely resemble human hearing development and physiology than previous models. This is particularly significant for the further development of novel inner ear therapies.
Complex research in interdisciplinary collaboration
“Creating genetically precisely modified primates is extraordinarily challenging from a reproductive and molecular biology perspectives. The fact that we succeeded in doing this for OTOF in marmosets demonstrates what is possible when reproductive biology, genome editing, and biomedical and veterinary research collaborate closely,” says Rüdiger Behr, head of the Stem Cell Biology and Regeneration Platform at the German Primate Center.
This project was made possible through close interdisciplinary collaboration between scientists at the German Primate Center, the University Medical Center Göttingen, and the Max Planck Institute for Multidisciplinary Sciences.
Prospects for the medicine of the future
The new model provides an important foundation for further developing gene therapies and other innovative approaches to treating hearing disorders. The goal is to better understand their safety, efficacy, and long-term stability. Furthermore, the precise genetic modification of marmosets opens up new possibilities for developing additional disease models and advancing therapies for previously incurable diseases.
“This model represents a major step forward for translational research,” says Marcus Jeschke, professor at the German Primate Center and at the University Medical Center Göttingen. “It offers the opportunity to test and optimize OTOF gene therapies and optogenetic cochlear implants under conditions that are significantly closer to human hearing than previous models.”
The work was funded by the Leibniz Cooperative Excellence Program, the DFG Cluster of Excellence MBExC, the DFG Collaborative Research Center 1690, and the Else Kröner Fresenius Center for Optogenetic Therapies.
The German Primate Center (DPZ) - Leibniz Institute for Primate Research conducts biological and biomedical research on and with primates in the fields of infection research, neuroscience and primate biology. The DPZ also maintains five field stations in the tropics and is a reference and service center for all aspects of primate research. The DPZ is one of the 96 research and infrastructure facilities of the Leibniz Association.