CRISPR can slow hearing loss in mice Ivaylo Sarayski / Alamy Stock Photo

Hearing loss in mice with a form of progressive deafness has been slowed by a one-off treatment using the CRISPR genome editing method. The approach might lead to a treatment that helps stave off hearing loss in people with certain forms of inherited deafness.

We have two copies of almost every gene in our body, but in some cases, a mutation in just one of these copies is enough to cause a disease. So-called dominant genetic disorders are caused by DNA alterations in just one copy of a gene, which leads to a faulty protein being made.

In theory, disorders like these could be cured by switching the mutated copy off, and leaving the healthy copy alone so that it can continue making the right protein. Researchers have now tried doing this using CRISPR.


They focused on a type of deafness known only as DFNA36. It is caused by a dominant mutation in one of the copies of a gene called Tmc1. The mutation is a change in a single DNA letter, and it slowly kills off the hair cells in our ear that detect sound. Children with this mutation start losing their hearing at around age 5, and may go completely deaf over the following decades.

Slowing down deafness

To disable faulty Tmc1 genes while leaving healthy copies alone, David Liu of Harvard University and his team made fatty capsules containing the CRISPR protein and an RNA guide designed to target only the faulty gene. They then injected these into the ears of mice.

Usually, mice carrying a mutant copy of Tmc1 develop serious hearing loss by the time they are four weeks old. By eight weeks, these mice aren’t startled at all by very loud sounds. But when such mice were given the CRISPR treatment, they responded to quieter sounds at four weeks, and were still able to hear very loud sounds at eight weeks.

This isn’t a complete cure. CRISPR disabled the mutant gene copy in around 10 per cent of cells. Correcting the mutant gene might work better than disabling it, and Liu is working on developing forms of the CRISPR protein that would be able to do this kind of editing.

The particular form of deafness caused by the dominant mutation of Tmc1 is extremely rare – only a few families are known to have it. But the same approach might work for other dominant forms of inherited deafness, which account for around a fifth of cases.

Journal reference: Nature, DOI: 10.1038/nature25164

Read more: Biohackers are using CRISPR on their DNA and we can’t stop it