‘Stuttering’ mice shed light on human speech impediment

About 70 million people worldwide stutter when they speak, and it turns out humans aren’t the only ones susceptible to verbal hiccups. Scientists at this year’s Society for Neuroscience Conference in Chicago, Illinois, show that mice, too, can stumble in their vocalizations. In humans, stuttering has long been linked to a mutation in the “housekeeping” gene Gnptab, which maintains basic levels of cellular function. To cement this curious genetic link, researchers decided to induce the Gnptab “stutter mutation” in mice. They suspected the change would trigger a mouse version of stammering. But deciphering stuttered squeaks is no easy task, so researchers set up a computerized model to register stutters through a statistical analysis of vocalizations. After applying the model to human speech, researchers boiled the verbal impediment down to two basic characteristics—fewer vocalizations in a given period of time and longer gaps in between each vocalization. For example, in 1 minute, stuttering humans made just 90 vocalizations compared with 125 for non-stutterers. Using these parameters to evaluate mouse vocalizations, researchers were able to identify stuttering mice over a 3.5-minute period. As expected, the mice carrying the mutated gene had far fewer vocalizations, with longer gaps between “speech” compared with their unmodified littermates—Gnptab mutant mice had about 80 vocalizations compared with 190 in the nonmutant mice. The findings not only supply evidence for Gnptab’s role in stuttering, but they also show that its function remains relatively consistent across multiple species. Scientists say the genetic parallel could help reveal the neural mechanisms behind stuttering, be it squeaking or speaking.www.elisakitgs.com