People who stutter can experience more depression symptoms and face a decreased quality of life. Despite this, there’s no available treatment at the moment. And we are only beginning to understand the causes of stuttering.
In the last few decades, studies on twin siblings have shown that stuttering has a strong genetic basis. But other factors may also come into play.
In 2010, geneticist Dennis Drayna and his collaborators first identified genes that are related to stuttering at the National Institute on Deafness and Other Communication Disorders, part of the National Institutes of Health.
Drayna and collaborators analyzed large families who came from the same ancestor and had members who stuttered in Cameroon, Brazil and Pakistan.
When analyzing the DNA of these families, they connected four genes to stuttering: GNPTAB, GNPTG, NAGPA and AP4E1. All of these genes encode proteins in the same biochemical process, which controls the recycling of damaged components in the cells and is present in most body cell types.
But these genes are known for other reasons, too. Mutations that completely shutdown GNPTAB, GNPTG or AP4E1 cause rare, severe and often fatal diseases. But in the case of stuttering, the proteins codified by the mutated genes retain some of their function. People carrying these mutations are perfectly healthy and have no other symptoms, other than stuttering.
