Scientists say a genetic link may explain why both autism and specific language difficulties can affect multiple members of the same family.
The research project leader Linda Brzustowicz, professor and chair of the genetics department at Rutgers, says that genes in a narrow region of two chromosomes (15q23-26 and 16p12) responsible for oral and written language impairments can result in similar behavioral characteristics with one family member developing autism and the other having only language impairment.
Specific language impairment is one of the most common learning disabilities, affecting an estimated 7 percent of children. It is not considered to be an autism spectrum disorder. It’s characterized by speech and language difficulties that can’t be explained by cognitive or physical problems.
Autism effects one in 88 children nationally—with nearly five times as many boys than girls diagnosed—about half of whom have some degree of language impairment.
“In this group of families we are trying to find genetic factors that might connect them,” says Brzustowicz. “This research is important because it is hard to understand autism until we find the genes that might be involved.”
While scientists don’t believe that there is one single gene that causes autism but rather a number of genes that increase the risk, Brzustowicz and her team of researchers are working to identify genetic patterns in these families in order to help gain a better understanding of the mechanisms that lead to autism, a developmental brain disorder that appears in the first three years of life.
In the Rutgers autism study, 79 families—mostly from New Jersey and Pennsylvania—with one child with autism and at least one with specific language impairment underwent extensive in-home testing.
Besides taking blood samples for genetic testing, family members including parents, children, and grandparents and in some cases even uncles, aunts, and cousins underwent a battery of tests to assess grammar, vocabulary, and language processing. The results are reported in a study published in the American Journal of Psychiatry.
“Our results indicate that there are shared patterns of DNA and visible behavioral characteristics across our group of study families,” says Judy Flax, an associate research professor working on the study with Brzustowicz.
In addition to the language findings, researchers also found strong evidence of a genetic link in the areas of obsessive-compulsive, repetitive behaviors, and social interaction skills, other symptoms associated with autism.
Brzustowicz says the next step will be to sequence the whole genome of those who participated in the study in order to compare the families to see if scientists can pinpoint any specific genes or mutations that are common to all.
“This is just the beginning,” says Brzustowicz. “We are finding evidence of genetic similarities with the hopes of being able to identify targets that might respond to pharmacological treatments.”
Christopher W. Bartlett, principal investigator in the Battelle Center for Mathematical Medicine at Nationwide Children’s Hospital, collaborated on the study.