A new study led by researchers at the University of Melbourne has found a link between a new genetic pathway and structural brain abnormalities in adult stutterers, opening up entirely new avenues of research to enhance understanding of persistent developmental stuttering.
The researchers studied 27 members of a four-generation Australian family, 13 of whom stuttered, in a study published in the journal Brain.
Stuttering is a speech disorder that affects about 5% of children and 1% of adults worldwide. In more than two-thirds of childhood cases, stuttering eventually resolves with treatment. However, in cases where stuttering is severe (as it is in most of the Australian families in this study), the disorder may persist into adulthood.
As early twin studies have shown, stuttering is usually hereditary, but previously we knew of only four genes associated with stuttering.
Michael Hildebrand and Angela Morgan led a large team of 18 researchers from international institutions to discover a 5th gene (PPID) associated with severe developmental stuttering and a chaperone protein (chaperone) pathway associated with the disorder.
Chaperones are proteins that transport other proteins into cells so they can fulfill their corresponding functions. The researchers suspect that the damaged gene alters the movement and function of the protein during brain development, triggering the neurological changes that lead to persistent stuttering.
Consistent with this speculation, mouse models with the same genetic defect showed structural changes in brain regions similar to those seen in members of the stuttering family.
Prof. Michael Hildebrand said, "We have long known that stuttering is genetically linked, but the novelty of this study is that it is the first to link structural brain abnormalities to developmental stuttering."
"These findings change the genetic diagnostic protocol for some people who stutter to include brain imaging studies. This study is important because it shows that genetic changes inherited in families can alter brain development, leading to structural abnormalities that bring on stuttering."
Professor Angela Morgan, a speech pathologist at the Murdoch Children's Research Institute (MCRI), said the research goes some way towards advancing understanding of the genetic predisposition to speech disorders. She said, "We know that environmental and genetic factors contribute to stuttering, and this study opens up further research into novel chaperonin pathways and related pathways, enhancing our understanding of the genetic structure of persistent developmental stuttering."
