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Gene therapy restores hearing in mice

23 Apr, 2013

A group of researchers from the United States have successfully restored the hearing and improved balance in mice with a congenital form of deafness modelled on the human equivalent.

According to the researchers, congenital hearing impairment can affect as many as 1 in 1000 newborns. Their new gene therapy approach, if implemented early, may correct hearing impairments in individuals with such mutations.

Usher syndrome

The research, published in Nature Medicine, involved injecting antisense oligonucleotides (single strands of DNA or RNA that are complementary to a chosen sequence) into newborn mice with mutations in the USH1C gene. Mutations in the USH1C gene can cause truncation of the protein harmonin – healthy versions of which are important for inner ear development. This truncated protein causes Usher syndrome in humans a condition that can cause combined deafness and blindness. Mice bearing this gene mutation are born deaf and exhibit head-tossing and circling behaviour caused by balance problems.

Injecting antisense oligonucleotides

Lead researcher Dr Michelle Hastings at the Rosalind Franklin University of Medicine and Science in Chicago and colleagues reported that the antisense oligonucleotides increased the amount of full-length harmonin protein produced in the mice. A single systemic injection improved low-frequency hearing and corrected head-tossing and circling behaviours. They also saw anatomical improvements in the number and structure of hair cells in the ear.

“These effects were sustained for several months, providing evidence that congenital deafness can be effectively overcome by treatment early in development to correct gene expression and demonstrating the therapeutic potential of antisense oligonucleotides in the treatment of deafness,” the authors wrote in their published report.

Animal model to treat human disease

In a press release, Rosalind Franklin co-lead author Dr Jennifer Lentz (Louisiana State University Health Sciences Center) said, "Successfully treating a human genetic disease in this animal model brings the possibility of treating patients much closer."

Dr Lentz has been studying Usher syndrome for almost 10 years and engineered the mice to model the human disease.


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