RECENT STUDIES ADD KNOWLEDGE ABOUT
GENETIC FACTORS IN STUTTERING
Two recent studies have once again focused attention on the role of genetic factors in stuttering. These studies used approaches not previously applied to stuttering, and identified new genetic variants correlated with this disorder. The first study was led by Jennifer Below at Vanderbilt University Medical Center, who studied their health
database, which contains over 92,000
individuals. The second, led by Shelly Jo Kraft at Wayne State University, studied an additional 16,000 individuals.
papers collaborated extensively with each other and with researchers at the University of North Carolina, the Irish Stammering Association, and Curtin University in Perth, Australia.
A problem they faced at the outset was that very few of the individuals in the Vanderbilt database (less than 2 tenths of one percent) had a clear diagnosis of stuttering based on standard criteria. Because stuttering is much more common than this, thought to exist in roughly 5 percent of all
8 The researchers on both
individuals, the investigators sought to identify others in their database who likely stuttered. This estimate identified over 9,000 individuals, or about 10 percent of everyone in their database, who were classified as likely affected with stuttering. The researchers then used an approach known as a genome-wide association study (GWAS) to study genetic variants, taking advantage of pre-existing genetic typing that had been done at hundreds of thousands of specific locations in the DNA of each of these individuals. Then, they compared the genetic variants present in those with predicted stuttering with the variants in those who were not predicted to stutter.
This
comparison identified one variant near the CYR1A gene on chromosome 2 as significantly associated in European ancestry populations, while a second variant in the ZMAT4 gene on chromosome 8 showed a very suggestive association in African ancestry populations. How these variants might act to affect the products of these genes or cause the clinical features of stuttering remains a fascinating challenge for the future.
SFA RESEARCH: UNDERSTANDING STUTTERING
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