In the KE family, one of 2,500 units of DNA that make up the FOXP2 gene is mutated. Monaco suggested that this mutation prevents FOXP2 from activating the normal sequence of genes required for early brain development.
"It is extraordinary that such a minute change in the gene is sufficient to disrupt a faculty as vital as language," he said.
Although humans have two copies of every gene, just one mutated copy of FOXP2—as in the case of both CS and the KE family—can have devastating effects on brain development, said Vargha-Khadem.
Brain imaging studies of the KE family revealed that affected members have abnormal basal ganglia—a region in the brain involved with movement—which could explain difficulty in moving the lips and tongue. Regions of the cortex involved in speech and language also appear aberrant.
The discovery of FOXP2 offers Monaco and other geneticists a probe to fish for other genes involved in development—specifically those directly controlled by FOXP2.
Also in progress is a collaborative project to study the evolution of the human FOXP2 gene by comparing it with versions in chimps and other primates. Monaco speculates that differences between the FOXP2 gene in humans and chimps may reveal a genetic basis for differing abilities to communicate.
|
SOURCES AND RELATED WEB SITES
|
