Autism Genetics: Two Studies

A gene linked to susceptibility to autism, CNTNAP2, has also been connected to specific language impairment, the most common childhood language disorder, as reported yesterday in Reuters. The study, A Functional Genetic Link between Distinct Developmental Language Disorders, is published in the New England Journal of Medicine.

Specific language impairment involves difficulties with language and, in particular, the repetition of nonsense words. Researchers analyzed CNTNAP2 function in 184 families with common language impairments; children with certain forms of the gene had certain difficulties with language, such as the repetition of nonsense words. It was found that FOXP2, which is mutated in people with a rare speech and language disorder, “directly regulates expression” of CNTNAP2. CNTNAP2 has also been linked to epilepsy, schizophrenia, and Tourette’s Syndrome and may not be specific only for language, but may also play a role in the early development of cognitive function. As noted in the Washington Post

“What skill in language-impaired children is this gene affecting?” said Dr. Karin Stromswold, author of an editorial accompanying the paper in the Nov. 6 issue of the New England Journal of Medicine. “There are a lot of reasons you can be language-impaired, excluding hearing loss and mental retardation.”

Many children with common language impairment also have motor impairment, so the gene could actually be affecting either core language or motor involvement, said Stromswold, a professor of psychology and member of the Rutgers University Center for Cognitive Science, in New Brunswick, N.J.

In their paper, the researchers suggest that “different components of autistic-spectrum disorders (communication deficits, impaired social interaction, and rigid or repetitive behaviors) may be under different genetic influences.”

Another study about autism genetics appears in the Journal of Medical Genetics and (as noted in the November 5th Vancouver Sun) suggests that disruptions in the gene, Contactin 4, stop the gene’s proper functioning and prevent the brain from making proper networks through the development of axons; the mutations are present from birth. 92 patients from 81 families with autism spectrum disorder participated and a whole genome analysis performed, and the results compared them to 560 people without autism. Three of the patients were found to have deletions or duplications of DNA that disrupted Contactin 4. In all the cases, these disruptions were inherited from fathers without a history of autism.