A Second Gene Supports Language

British scientists have identified a second gene that is crucial to normal language development. The gene, CNTNAP2, joins FOXP2 as critical to understanding the biology of language.

The classic idea about a gene is that it makes a protein. For example, a gene might make the protein that gives some eyes their blue color. FOXP2, however, works differently. Instead of directly making a protein, FOXP2 genes regulate the making of proteins by other genes. A team of researchers at the Wellcome Trust Centre for Human Genetics  has now identified the CNTNAP2 gene as one that FOXP2 regulates. Certain unusual mutations of CNTNAP2 are implicated in both autism and specific language impairment.  The team’s paper, published today (Nov. 5) in the New England Journal of Medicine, concludes that we now have a biological link “between clinically distinct syndromes involving disrupted language.”

Specific language impairment (SLI), affects up to 7% of 5- or 6- year-olds and is much more common than the impaired speech brought on by FOXP2 mutations. SLI is often found among many different members of a family and has long been considered likely to be hereditary. Studies have found no link between SLI and FOXP2. Nevertheless, the authors hypothesized that genetic associations with disorders such as SLI could be found “downstream” from FOXP2 influence. In other words, they suspected that by following FOXP2’s influence on other genes, they might discover the source of further genetically-based language disorders.

Working in the laboratory with human neurons, the team determined that one of the genes regulated by FOXP2 is CNTNAP2. To state it technically: CNTNAP2 is a target of FOXP2. The CNTNAP2 gene does work like a normal gene, making a protein. In its case it makes a kind of protein thought in humans to be “involved in cortical development.” It helps build the brain.

Having identified the gene as possibly important to language the team studied the genetic traits of 184 families known to be affected with SLI. Analysis established that some variants of CNTNAP2 are associated with SLI. Other unrelated work has shown that variant forms of the same gene are implicated in autism.

The test used in the study to identify people with SLI appears to have measured their ability to remember sounds. They scored low in their capacity to hear a nonsense syllable and repeated it. But despite these associations between various language disorders and CNTNAP2, we do not yet know how the genes supports normal speech. Its evolutionary history is also uncertain. In an e-mail to this blog, team leader Simon E. Fisher reports that CNTNAP2 "is one of the largest genes in the human genome, with a lot of intronic sequence [portions not used in coding protein]which might harbour important regulatory elements."

Understandably then, the team ends its report with a very narrow boast:

This work represents a move … toward an understanding of molecular networks that may go awry in neurodevelopmental disorders affecting language.

It is not an answer to the questions asked on this blog, but it is always promising when an explorer cries out, “Hey, over here. I’ve found something.”

 

Comments

[dan howitt]

Interesting article, thanks for it.
Dan Howitt