ASU assistant professor's study finds new candidates for genetic cause of disorder; could mean much earlier diagnosis in infants
People take preventative measures every day. We use seat belts to prevent injury, wear sunscreen to prevent skin damage and lock our doors to prevent burglaries. Any way you look at it, preventing a disaster is preferable to dealing with its aftermath.
The same holds true for medical disorders; prevention is always better than attempting to treat after diagnosis. For a great number of disorders, that’s not always possible. But thanks to the research of ASU assistant professor Beate PeterBeate Peter is an assistant professor of speech and hearing in Arizona State University’s College of Health Solutions., we are one step closer to being able to do this for childhood apraxia of speech, or CAS.
In a study published today in the leading scientific journal PLOS ONE, Peter (pictured above) details how she was able to identify mutations in mainly two genes that may cause the disorder. Knowing more about the genetics of speech problems will allow parents with children at risk for the disorder to take action earlier than was previously possible.
CAS is a motor speech disorder that affects roughly one to two of every 1,000 childrenAccording to the American Speech-Language Hearing Association, http://www.asha.org/PRPSpecificTopic.aspx?folderid=8589935338§ion=Incidence_and_Prevalence . Children with CAS have problems saying certain sounds and words because they have trouble orchestrating all the different muscles in their speech system. This makes it extremely difficult for them to convey their thoughts and emotions. Peter calls the disorder “a great source of frustration” to the children it affects as well as their families, often causing children to act out or — worse — give up on speaking altogether.
“One mother once told me, ‘He doesn’t have any friends — none of the kids at preschool want to play with him,’ ” Peter said. “So there is a huge area of need … to do more than just wait until they have a diagnosis and then treat.”
A former school-based speech-language pathologist, Peter thought that perhaps the answer to filling that need lay in our genes. And so in this, her latest study, Peter chose two separate families in which incidences of CAS were very high to delve into the genetics of speech disorders.
After running a battery of tests on the family members and asking them lots of questions to determine who among them did and did not have speech problems came the “most crucial” step: obtaining a DNA sample from each member of each family. For each of these DNA samples, Peter obtained computer files with more than half a million genetic markers spread across all chromosomes (imagine a huge text file with the markers for one entire family: dozens of columns and more than 9 million lines), and for a few samples, she also obtained computer files with readouts of the entire exome, which consists of all pieces of DNA that contain the recipes for making proteins.
Using a program developed by researchers at her alma mater the University of Washington, Peter fed each family’s genetic marker files into a computer to look for parts of chromosomes that likely were inherited along with the speech problem. Once she found these chromosomal regions, she checked them for harmful exome variants that were inherited only by family members with the speech problem.
What she found was that members of each family who were previously determined to have a speech problem also shared a specific gene marker. Members of each family who were previously determined not to have a speech problem did not have that specific gene marker; an indication that most likely, the gene marker shared by members of the family who have a speech problem is indicative of a shared genetic anomaly that likely caused the speech disorder.
For the first family, Peter found one specific gene variant on one chromosome and several others on another chromosome that were shared by members of the family with a speech problem. For the second family, she found only one specific gene variant shared by members of the family with a speech problem.
Hence, these candidate variants may cause the disorder.