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Scientists have used a new genetic-engineering technique to prevent deafness in mice. The hope is that someday it could help doctors do the same thing for people. As NPR health correspondent Rob Stein reports, this is the latest development in the rapidly growing field of gene therapy.
ROB STEIN, BYLINE: We all know one of the most famous people to lose one of their most important senses...
(SOUNDBITE OF BEETHOVEN'S SYMPHONY NO. 5)
STEIN: ...Beethoven, the German composer who gave the world "Symphony No. 5" and so much more glorious music, even as his own symphonies faded to silence in his own ears.
(SOUNDBITE OF BEETHOVEN'S SYMPHONY NO. 5)
STEIN: So when David Liu decided to use genetic engineering to try to prevent deafness, he started with a mouse named after...
DAVID LIU: Ludwig van Beethoven.
STEIN: ...Because these Beethoven mice carry a genetic defect that makes them go deaf, too. It's probably not what stole Beethoven's hearing, but the same defect runs in some families.
LIU: Humans that are born with even one bad copy of this gene experience progressive hearing loss that's evident in their early childhood, and by the time they reach sort of late childhood, they are profoundly deaf.
STEIN: Because this mutant gene destroys the tiny sensory hairs inside the ear that let us hear. Liu's a gene-editing expert at Harvard and MIT. So he designed a genetic scalpel to splice out this bad gene and injected it into the ears of these Beethoven mouse pups one day after they were born.
LIU: And then it homes in on the mutant gene. It cuts the DNA so that mutant gene can no longer poison the hair cells and cause the hair cells to eventually die.
STEIN: Giving the mice enough healthy hair cells in their ears to save their hearing. When Liu tested the gene-edited mice a month later, he was thrilled. It worked.
LIU: The ears that were injected with our treatment were hearing sounds that were about as quiet as a normal, quiet conversation, whereas the uninjected ears of the same mice have lost enough of their hearing that they required sounds that were about as loud as a garbage disposal in order to register a response. So it's quite a bit of difference.
STEIN: Now, Liu stresses it will take a lot more research before anyone tries something like this on people. But he hopes the same thing could eventually prevent many kinds of inherited deafness. And that's not all.
LIU: We and others are interested in developing different kinds of genome-editing strategies to actually try to restore hearing by stimulating actual regeneration of hair cells, which has the promise of potentially treating not just genetic forms of hearing loss but maybe even environmental forms as well.
STEIN: Like deafness caused by loud noise or infections. Other researchers say the advance is a big deal. Fyodor Urnov is a genetic engineer at the Altius Institute for Biomedical Sciences in Seattle. He says it shows how gene-editing techniques are revolutionizing medicine.
FYODOR URNOV: It is an extraordinary thrill to be working in this field at this time. We no longer are relegated to just sequencing DNA and staring glumly at genetic destiny.
STEIN: While a lot more research is needed before anyone cures deafness with gene editing, the Food and Drug Administration recently approved the first gene therapies, one for leukemia and another for lymphoma, and OK'd another to reverse a rare form of genetic blindness just yesterday. In the meantime, scientists are testing gene-editing therapies for many other diseases. Rob Stein, NPR News.
(SOUNDBITE OF BEETHOVEN'S SYMPHONY NO. 5) Transcript provided by NPR, Copyright NPR.
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