Reengineering Life is a series from OneZero about the astonishing ways genetic technology is changing humanity and the world around us.
Researchers at Boston Children’s Hospital and the Broad Institute of MIT and Harvard recently took a step toward a future where hereditary deafness could be corrected with a single injection into the ear. They used a super-precise type of gene editing to temporarily improve hearing in deaf lab mice.
The technique, known as base editing — sometimes called CRISPR 2.0 — allowed them to repair a mutation in the TMC1 gene. Babies who inherit this mutation from both parents lose their hearing at just four weeks old.
Two to three out of every 1,000 children born in the United States have a diminished level of hearing or can’t hear at all. Around half of these children are born this way because of genes they inherit from their parents.
Although hearing loss can be treated with hearing aids and cochlear implants, these technologies don’t correct an underlying genetic problem. Hearing aids simply amplify sounds so that they can be detected by damaged ears, while cochlear implants bypass damaged parts of the ear completely. Currently, there are no treatments available that can directly correct the genetic mutations that cause deafness.
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Genes are made up of sequences of four chemical bases known as A, C, G, and T. These bases appear in pairs; C always pairs with G, and A always pairs with T. Mutations in a gene arise when these bases occur in the wrong order. While the gene-editing tool CRISPR can delete or edit whole genes, base editing can swap out just one of these base pairs for another.
The researchers tested their base editing technique on deaf mice bred to have the TMC1 mutation, converting a C-G base pair into a T-A pair, which corrected the…