Study points to chromosome site of autism gene

November 30, 1999

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

Autism is considered a severe neuro-developmental disorder defined by social and communication deficits and ritualistic-repetitive behaviors that are detectable in early childhood and continue throughout life.

"For a long time autism was not viewed as being a genetic disorder," says Dr. Joseph Piven, 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%."

According to the child psychiatrist, families with an autistic child run up to a 5% risk of having a second child with autism. "And while that percentage is not so high, it's substantially higher than the rate of autism in the general population, which is approximately five in 10,000 kids. The data is pretty overwhelming that autism is strongly genetic, more so than schizophrenia or diabetes."

Still, despite epidemiology evidence of a strong genetic influence, Piven and his collaborators note that 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. This investigation involved 75 families with at least two autistic children, including three families having three 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 these regions was significantly greater than chance. For a region of chromosome 13, the answer was yes.

The study also highlighted several other possible DNA hot spots for autism genes, notably a region on chromosome 7. This latter finding confirms a report last year by an international autism research team.

The new evidence also converges with that from another research group for a location in the same region of chromosome 7 that is currently implicated in some form of specific speech and language impairment, a disorder having characteristics that overlap that of autism.

"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."

In the second stage of the project, also funded by the National Institutes of Health, the research group will add 100 new families for a follow-up analysis. "By comparing results across a number of studies, we expect to be able to narrow our search for autism susceptibility genes to a small number of genomic regions," they state.

Participating institutions include New England Medical Center/Tufts University School of Medicine, Vanderbilt University School of Medicine, University of Iowa College of Medicine, The Johns Hopkins University School of Medicine, and Harvard University School of Public Health.

In addition to the genetics of autism, Piven also uses neuroimaging (with MRI) to study structural differences in the brain of autistic individuals. He was the first to report that brain size is greater in autistic persons, an enlargement that may be due to certain timing during the process of neuronal development.

With new funding from the National Institute of Mental Health, Piven's Center is conducting a longitudinal study of children aged 18-to-35 months with autism or probable autism.

"Basically, we want to look at the size and shape of the brain to gain insights into this observation of enlargement, that it may encompass some developmental abnormalities in the brain during early postnatal development," he says. Piven's neuroimaging project will enroll 35-40 children and follow them into early childhood.

Beyond autism, Piven says the Center will provide a resource to facilitate the study of mental retardation and other developmental disorders including fragile X syndrome.
Note to reporters: Contact Dr. Joseph Piven at 919-843-8641; e-mail:

UNC-CH School of Medicine contact: Lynn Wooten, 919-966-6046; e-mail:

University of North Carolina Health Care

Related Autism Articles from Brightsurf:

Autism-cholesterol link
Study identifies genetic link between cholesterol alterations and autism.

National Autism Indicators Report: the connection between autism and financial hardship
A.J. Drexel Autism Institute released the 2020 National Autism Indicators Report highlighting the financial challenges facing households of children with autism spectrum disorder (ASD), including higher levels of poverty, material hardship and medical expenses.

Autism risk estimated at 3 to 5% for children whose parents have a sibling with autism
Roughly 3 to 5% of children with an aunt or uncle with autism spectrum disorder (ASD) can also be expected to have ASD, compared to about 1.5% of children in the general population, according to a study funded by the National Institutes of Health.

Adulthood with autism
The independence that comes with growing up can be scary for any teenager, but for young adults with autism spectrum disorder and their caregivers, the transition from adolescence to adulthood can seem particularly daunting.

Brain protein mutation from child with autism causes autism-like behavioral change in mice
A de novo gene mutation that encodes a brain protein in a child with autism has been placed into the brains of mice.

Autism and theory of mind
Theory of mind, or the ability to represent other people's minds as distinct from one's own, can be difficult for people with autism.

Potential biomarker for autism
A study of young children with autism spectrum disorder published in JNeurosci reveals altered brain waves compared to typically developing children during a motor control task.

Autism often associated with multiple new mutations
Most autism cases are in families with no previous history of the disorder.

State laws requiring autism coverage by private insurers led to increases in autism care
A new study led by researchers at the Johns Hopkins Bloomberg School of Public Health has found that the enactment of state laws mandating coverage of autism spectrum disorder (ASD) was followed by sizable increases in insurer-covered ASD care and associated spending.

Autism's gender patterns
Having one child with autism is a well-known risk factor for having another one with the same disorder, but whether and how a sibling's gender influences this risk has remained largely unknown.

Read More: Autism News and Autism Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to