These days, hearing loss comes in all sorts of shapes and sizes. While some people experience age-related hearing loss later in life, others develop hearing loss as teenagers or young adults. However, many people fail to realize that babies can have hearing loss, too.
The Centers for Disease Control estimate that between 50% and 60% of babies with hearing loss have this condition thanks to a genetic cause. This genetic hearing loss, called hereditary hearing loss, is more common than most people would think and can be caused by over 100 currently identified genes.
While we’ve made many advancements in the field of hearing healthcare, we haven’t yet found a way to prevent or cure hereditary hearing loss – until now. Thanks to some novel research conducted by scientists at Harvard Medical School and Boston Children’s Hospital, we may be closer than ever to preventing hereditary hearing loss in babies and young children.
Using a new and innovative gene-editing approach, researchers at Harvard and Boston Children’s Hospital were able to protect the hearing of mice with hereditary hearing loss. The recent research was conducted on special rodents, known as Beethoven mice, who were treated for a gene mutation that causes progressive hearing loss in humans.
This form of progressive hearing loss usually results in profound deafness in an individual with the gene mutation by their mid-twenties. While progressive hereditary hearing loss can, and does, have a huge impact on an individual’s life, it is often caused by a single gene mutation in a person’s DNA.
Thus, to treat the Beethoven mice, the researchers used a newly developed version of the CRISPR-Cas9 gene-editing system to selectively disable the mutated version of the gene in each mouse. Since we all inherit two copies of genes – one from each parent – the scientists could “mute” the troublesome gene while allowing the normal gene to continue doing its job.
After receiving the innovative new treatment, the Beethoven mice in this study were able to detect sounds at around 45 decibels, which is about the level of normal conversation. Since Beethoven mice are normally profoundly deaf by six months of age, the treated mice demonstrated a level of hearing that’s 16 times better than their untreated counterparts. That’s something to be excited about.
Although some bodily functions require the actions of both of the two copies of each gene, many can happen with no ill-effect with just one healthy function of the disease. The kind of treatment used on the Beethoven mice only works with recessively inherited genetic disorders, however, because with a dominantly inherited disorder, a single problematic gene can result in disease.
That being said, the researcher’s success in treating this hereditary hearing loss in mice with no testable ill-effects is the next step in developing precision medicine techniques for helping individuals with recessively inherited genetic disorders. What’s interesting about this process, however, is not that it can disable the mutant gene, but that it does so without affecting the healthy gene, too.
Basically, the CRISPR-Cas9 gene-editing process can identify the target mutant gene and cut it out of the genome. While the process is very advanced, though, there is still a risk of cutting the wrong DNA. So, while this new research leaves much to be excited about, it’s not quite ready to be used on humans.
Moving forward, this research can be used as the baseline for future gene-editing therapies. Although the CRISPR-Cas9 gene-editing process isn’t quite ready to be used in healthcare, its success in this study does show that highly targeted gene treatments have the potential to make a huge difference in the lives of people with hereditary deafness around the world.