CRISPR Gene Editing Restores Hearing in Mice
A groundbreaking study Wenliang et al. offers new hope for those suffering from inherited hearing loss.
By Yash Laddha
Scientists have developed a genome editing technique that restored hearing in adult mice with a rare genetic disorder. This approach could eventually lead to treatments for humans with similar genetic conditions.
The Challenge of Genetic Deafness
Inherited hearing loss affects many children, with a single genetic abnormality often being the culprit. Known as genetic or inherited deafness, this condition can severely impact a child’s speech, language, and social development. While early interventions can help, current treatments are limited, and no medications are approved to slow or reverse this type of hearing loss.
One of the most challenging forms of genetic hearing loss is caused by mutations in the MIR96 gene. This gene is essential for the proper function of hair cells in the inner ear, which are responsible for converting sound into electrical signals that the brain can interpret. In humans, mutations in MIR96 lead to autosomal dominant deafness-50 (DFNA50), a condition that typically results in progressive hearing loss beginning in adolescence.
The Research Breakthrough
Researchers at Mass Eye and Ear in Boston, led by Dr. Zheng-Yi Chen, have made a significant advancement in gene editing to address this issue. Unlike previous studies that focused on newborn mice, this research targeted adult mice with fully mature inner ears. This approach is more relevant to human applications, as the inner ear structures in newborn humans are already fully developed.
The team created a mouse model with a specific mutation in the MIR96 gene. In these mice, the mutation causes the loss of hair cells and complete hearing loss in high frequencies four weeks after birth. The researchers utilized the CRISPR-Cas9 gene editing system to target and disable the faulty MIR96 gene. To deliver this system, they used a harmless adeno-associated virus (AAV), which was injected into the inner ear of the mice.
Methodology and Results
The experiment involved two groups of mutant mice: one group received the gene editing injection at three weeks of age, before the onset of hearing loss, while the other group was treated at six weeks, when they were already experiencing hearing loss. Each mouse received the injection in one ear, with the other ear serving as a control.
The results were groundbreaking. In both groups of mice, the treated ear showed better survival of hair cells and improved long-term hearing compared to the untreated ear. The earlier intervention proved to be more effective, with the mice receiving treatment at three weeks exhibiting more significant improvements.
Moreover, the safety of the treatment was confirmed. The AAV used in the procedure did not integrate into the mice’s genome, reducing the risk of unexpected and potentially harmful outcomes. The researchers observed sustained improvements in hearing for at least nine months post-treatment, indicating that the benefits of the gene editing were long-lasting.
Implications for Human Treatment
A major advancement in the field of genetic therapies for hearing loss has been made by this research. The study opens the door for possible human applications by showing that genome editing can restore hearing in mature organisms. However, more preclinical research in various animal models is required to fully assess the safety and efficacy of this strategy before it can be tested in people.
