The discovery of the CNTNAP2 gene, which has recently been implicated in autism, may act as a crucial genetic link between the two disorders.
SLI is the most common language disorder, in which children develop unexplained difficulties in producing and understanding language
In the new study by researchers at the Wellcome Trust Centre for Human Genetics, University of Oxford, it was found particular variants of the CNTNAP2 gene were significantly associated with language deficits in a large sample of families with SLI.
"It has long been suspected that inherited factors play an important role in childhood language disorders. But this is the first time that we have been able to implicate variants of a specific gene in common forms of language impairment," said Dr Simon Fisher, a Royal Society Research Fellow at the Wellcome Trust Centre, who led the research.
Fro the study, the researchers first studied another language-related gene, called FOXP2, versions of which are found in many animals, including primates, birds, bats and mice. FOXP2 acts to regulate other genes in the brain, switching them on and off.
The researchers initially analysed human neurons grown in the laboratory in order to search for these target genes. They identified CNTNAP2 as a key part of the network.
Later, when they went on to investigate CNTNAP2 in 184 families with common language impairments, they found that children who carried certain variants of the gene displayed reduced language abilities, most strikingly for a measure of nonsense-word repetition that is known to be a strong indicator of SLI.
In fact, many recent studies have also implicated CNTNAP2 in autism, a syndrome characterised by communication deficits, impaired social interaction, and repetitive behaviours.
Especially, one investigation uncovered a link between variants of CNTNAP2 and delayed language development in children with autism.
"Our findings suggest that similar changes in the regulation or function of this gene could be involved in language deficits in both SLI and autism. This supports the emerging view that autism involves the convergence of a number of distinct problems underpinned by different genetic effects," said Dr Fisher.
The study was published in the New England Journal of Medicine.