Mice supposedly cannot speak, so they obviously cannot stutter. But, tinkering with a certain gene that is known to be involved in human speech, researchers have now created transgenic mice that produce pups with altered vocalization in a way that is similar to humans' stuttering. These mice can make a good model for a better understanding of stuttering, and can illuminate how mutations to the gene Gnptab can cause this speech disorder.
Gnptab encodes a protein that helps to direct enzymes into the lysosome - a compartment which breaks down waste and recycles old cellular machinery in animal cells. Mutations to other genes in this system are known to lead to the build up of waste products and often result in serious diseases, such as the well known Tay Sachs disease. Although there are many known diseases and disorders in this area, how mutations in the gene Gnptab cause stuttering is still unknown.
Neuroscientist Terra Barnes and her team produced mice with a mutation in the Gnptab gene and studied the ultrasonic vocalizations emitted from the pups when removed from their mothers. The team designed a computer system that listens for stuttering vocalization patterns. The program revealed that mice with the mutant copies of the Gnptab produced less frequent vocalizations and longer pauses than normal mice. However, the affected mice mice produced the same sounds in the same proportions as their wildtype siblings, which indicated they were still capable of producing normal sounds.
Despite the vast differences in vocalizations between human and mice, the researchers believe this information can further our understanding of the causation of stutters and serve as a valuable model. But, as of now, it is still unknown how a single mutation to a common cellular housekeeping gene can result in stuttered speech. Although no evidence yet, it is possible that the neurons associated in speech are particularly sensitive to waste accumulation caused by missing lysosomal enzymes; yet, scientists are not even sure what neurons are involved in speech.
I believe this research is only the beginning to a groundbreaking finding. When this research is solidified and scientists find out exactly how a single mutation to the Gnptab gene can effect stuttering, it will change the way speech-language pathologists and doctors treat patients with speech impediments. This will benefit patients and make for better clinical outcomes. One thing that surprises me is that scientists still are not sure what neurons are involved in speech. How is this possible in this day and age? I feel like we are so advanced in medicine and genomics at this point in time, it is hard to believe we still are not sure what neurons are involved in such an important part of life - speech.