Possible Autism Gene on Chromosome 13 - Brief Article

Applied Genetics News, Dec 19, 1999

Researchers at the University of North Carolina at Chapel Hill (UNC-CH) and collaborating institutions are reporting evidence for a possible gene on chromosome 13 that may contribute to autism. The group's report will be published December 15 in the American Journal of Medical Genetics.

"For a long time autism was not viewed as being a genetic disorder," says Joseph Piven, (Tel: 919/843-8641, Email: jpiven@css.unc.edu) formerly of Iowa University, now UNC-CH professor of psychiatry and new director of the university's mental retardation and developmental disabilities research center. "It has a high degree of heritability, confirmed by twin studies that show a substantially higher rate in identical twins--so much so that heritability is over 90%."

The search for autism genes has only recently begun in earnest. The new study is one of a handful worldwide to genetically screen the DNA of nuclear families of autistic siblings. The Chapel Hill investigation involved 75 families with at least 2 autistic children, including 3 families having 3 autistic children. Children's ages ranged from 3 to 31 years old.

Findings were based on an assessment of participants' DNA prepared from blood samples. The researchers spaced 416 nucleotide markers on selected chromosome regions for each individual. The markers helped identify those regions across individuals containing similar clusters of nucleotide sequences. Statistical analysis then determined if the presence of regions was significantly greater than chance. The site on chromosome 13 was identified in this way. A region on chromosome 7 was also identified, consistent with a previous published report.

"We believe there must be more than one gene involved in autism," Piven says. "As in all complex behavioral disorders, there's no clear evidence when looking at family pedigrees or family trees that suggests a single-gene may underlie this disorder."

Piven has also used imaging techniques to identify structural differences in the brain of autistic individuals. Surprisingly, he has found that autistic children actually have larger brains than their normal counterparts.