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New Research May Help Explain the Genetic Roots of Autism

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Duke Health News 919-660-1306

SAN DIEGO, Calif. – Duke University Medical Center
researchers have found evidence of a genetic link between
autism and several chromosomomal anomalies. These findings, in
addition to other recent Duke research discoveries on the
genetics of autism, will be presented at the International
Meeting for Autism Research Friday and Saturday (Nov. 9-10) in
San Diego.

Another presentation by Duke researchers includes findings
that show a possible link between autism and Rett's disorder, a
developmental illness primarily occurring in girls that is
characterized by profound mental retardation.

On Friday, they also announced a new consumer Web site
dedicated to the genetics of autism.

Autism is a complex disease that affects from two to 10 per
10,000 people, making it the third most common developmental
disability. However, because the disease presents varying
symptoms, doctors have difficulty diagnosing it with certainty.
Some autistic children simply talk later than normal, while
others severely withdraw or display self-destructive patterns,
such as repetitive head banging.

The evidence for a genetic basis for autism has been well
established. To date, more than five possible loci, or specific
regions of DNA, have been identified that could potentially
lead to an increased risk of autism.

"Duke is making a major commitment to research in the
genetics of autism and related disorders," said Margaret
Pericak-Vance, director of the Center for Human Genetics at
Duke. "Genetics will help us find the underlying cause of
autism. If we find the underlying cause, it will help us target
possible therapies and keys to prevention."

The research projects were led by Pericak-Vance and John R.
Gilbert, Ph.D., of the division of medical genetics in Duke's
department of medicine.

Duke Study Points to Chromosomomal Anomalies Suspected of
Being Involved in Autism

Duke researchers have identified seven chromosomal anomalies
on six chromosomes in 12 children with autism. The findings
indicate the anomalies might be associated with autism. If so,
they are significant because they could help researchers
identify genes involved in causing autism, said Chantelle
Wolpert, a research associate with the Duke Center for Human
Genetics.

"Chromosome anomalies can occur by chance and may be
unrelated to autism. Our job now is to sort out which anomalies
are due to chance and which ones are involved in causing
autism," Wolpert said.

A chromosomal anomaly is an extra piece, or sometimes a
missing piece, of a chromosome. Chromosomal anomalies have been
associated with Down syndrome, in which a child inherits an
extra piece of chromosome 21.

The researchers examined the frequency of chromosomal
anomalies in 333 patients with autism. They identified
anomalies on regions of chromosomes 2, 7, 15, 18 and X. Some
anomalies were identified more than once.

They also identified, in one child, a Robertsonian
translocation anomaly involving chromosomes 13 and 14. A
Robertsonian translocation occurs when two chromosomes fuse
together; in this case, chromosomes 13 and 14 joined together,
leaving an individual with 45 chromosomes instead of 46.

One of the anomalies, an extra piece of chromosome 15, was
found in five children. "The repeated occurrence of this
particular anomaly suggests that it may be involved with
autism, but we have more work to do to prove this.

"It has been reported before that in some children with
autism, there is an extra piece of chromosome 15, but in this
study, we look at a series of families, which offers more
conclusive evidence.

"Previously, some scientists doubted whether chromosomal
anomalies, such as those on chromosome 15, could lead to
autism. But in our study we are beginning to build a case that
this chromosomal abnormality could possibly cause autistic
disorder," Wolpert said.

DUKE STUDY FINDS LINK BETWEEN AUTISTIC DISORDERS AND RETT'S
SYNDROME

Duke researchers have found genetic mutations in the MeCP2
gene of two girls diagnosed with autism. The finding is
significant because MeCP2 has been implicated in Rett's
disorder, a pervasive developmental disorder characterized by
profound mental retardation.

The study focused on 69 females who were diagnosed with
autism but did not show any clinical signs of Rett's disorder.
Researchers conducted genetic tests to look for the presence of
mutations in the MeCP2 gene, which they found in two of the
girls. "This is significant because these were individuals who
did not fit the classic phenotype of Rett. It suggests that we
really need to look more carefully at our populations because
this genetic mutation might be present in individuals thought
to have autism," said Dr. Michael Cuccaro, associate professor
of neuropsychiatry at the University of South Carolina,
Columbia, and a collaborator on the project. Cuccaro has
accepted a position with the Center for Human Genetics at Duke
and will officially join the Duke team on Dec. 1.

In girls with Rett's disorder, very early development is
normal but, as the child ages, the characteristics of Rett's
disorder, such as smaller than normal head size (a condition
called microcephaly) and loss of ability to control one's
hands, begin to surface. Generally, Rett's disorder, which
primarily strikes girls, is a progressive disease that
ultimately leads to severe mental retardation by early
adulthood.

The finding will help genetic researchers better understand
the underlying causes of autism and Rett's disorder.

While it is known that there are many complex genetic roots
to autism, Cuccaro said, the genetics of Rett's disorder, are
comparatively simpler – more than 80 percent of patients
diagnosed with Rett's have a specific mutation in the MeCP2
gene on the X chromosome. This mutation is not inherited, but
occurs after conception.

WEB SITE FOCUSES ON ADVANCES IN GENETICS-BASED AUTISM
RESEARCH

The Duke Center for Human Genetics, in conjunction with Dr.
Susan Folstein at Tufts University and the National Alliance
for Autism Research, is preparing to launch a Web site
dedicated to highlighting advances in genetics-based autism
research.

The Web site www.exploringautism.org will inform parents of
advances in genetics based research, said Margaret
Pericak-Vance, director of Duke's Center for Human Genetics and
director of the Web site.

"This Web site is dedicated to helping families who are
living with the challenges of autism stay informed about the
exciting breakthroughs surrounding the genetics of autism. We
will explain genetic principles as they relate to autism,
provide the latest research news and seek input from parents.
Together we will work to increase the body of knowledge about
autism.

"As research teams around the globe seek to understand the
genetic contribution to autism, we are hopeful that we will
develop effective treatments for autism and the disorders
related to it," she said.

The Web site will feature: the story of a family in which
two of three young sons have been diagnosed with autism; a
genetics primer for parents; an easy-to-understand diagnostic
summary of pervasive developmental disorders; and a lay
language summary of the status of genetic research findings in
autistic disorder.

The Web site, which is funded by the National Alliance for
Autism Research, will be launched Jan. 1, 2002.

The Center for Human Genetics is one of five research
centers within Duke's Institute for Genome Sciences and Policy
(IGSP). The IGSP, established in 2000 with $200 million in
institutional funds, also includes: the Center for Genome
Technology, the Center for Human Disease Models, the Center for
Bioinformatics and Computational Biology and the Center for
Genome Ethics, Law and Policy.

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