LAWRENCE — Language development in toddlers usually proceeds from gestures and garbled sounds into words and eventually full sentences. But for some children, language development can be delayed – even when there is no clear evidence of neurological, sensory-intellectual or emotional problems.
For these children, specific language impairment, or SLI, affects their ability to acquire a language. The estimated prevalence of SLI in children is 7% in the United States. It can persist into adulthood. Children with SLI are normally at the higher risk of lower academic achievement, difficulty in developing peer relationships, social anxiety in early childhood and reading impairments. Twin and family aggregation studies indicate that genetic factors are involved in SLI. However, the underlying genetic influences are not well-known in this disorder.
To study the genetics of this disorder, M. Hashim Raza, KU assistant professor in the Child Language Doctoral Program, has been awarded $439,782 through the National Institutes of Health for a three-year project focused on extended families in Pakistan.
Consanguinity, or cousin marriages, are prevalent in Pakistan and increase the risk of inherited disorders. The custom, which helps retain wealth and family traditions, is relatively common in some Middle East and South Asian countries. In Pakistan and Saudi Arabia, up to 70% of marriages are consanguineous. However, it can lead to higher chances to inherit identical copies of detrimental genes, which leads to increased risks of genetic disorders such as SLI.
According to Raza, genetic studies of large consanguineous families with SLI are important to identify the gene pathways involved in this poorly understood, genetically complex disorder. Studying such large families with well-defined phenotypes, or sets of characteristics, are needed to increase the likelihood of identifying genes affiliated with the disorder.
Some of the premises for this project are previous findings and research by Raza and colleagues on the family-based genetic nature of persistent stuttering. Genetic causes of stuttering were not precisely understood when Raza and researchers at the National Institutes of Health successfully mapped several genes and, for the first time, identified gene mutations associated with stuttering in 2010 and 2015 by studying extended families from Pakistan, West Africa, Brazil and the United States.
He said that the long-term goal of the project is to further understand how gene pathways are involved in the development of typical and atypical language.
“The genetic studies of unusual families with defined phenotypes help us to map genomic regions with high confidence, leads to identify the particular genes,” he said. “Once we are able to find the genes, we can target those genes in multiple populations to find the prevalence of the genetic variations associated with this disorder.”