Re: Scientists Identify Genetic Link To Autism

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http://news.biocompare.com/newsstory.asp?id=211545

UCLA Scientists Identify New Genetic Link to Autism

1/10/2008

Source: University of California - Los Angeles

Presence in early brain's language centers may explain speech delay

UCLA scientists have used language onset – the age when a child

speaks his first word – as a tool for identifying a new gene linked

to autism. The team also discovered that the gene is most active in

brain regions involved with language and thought. Interestingly,

evidence for the genetic link came from the DNA of families with

autistic boys, not those with autistic girls.

The American Journal of Human Genetics publishes the findings in its

Jan. 10 online edition, which also features two studies from research

teams at Yale and s Hopkins that used different methods that

pinpointed the same gene. The coincidence suggests that the gene,

called contactin-associated protein-like 2 (CNTNAP2), likely plays a

key role in the development of autism.

" This gene not only may predispose children to autism, " said Dr.

Geschwind, principal investigator and Gordon and Virginia

Mac Distinguished Professor of Human Genetics at the

Geffen School of Medicine. " It also may influence the development of

brain structures involved in language, providing a tangible link

between genes, the brain and behavior. "

Children normally utter their first word by age 1. Children with

autism, however, can be speech-delayed by many months or even years.

Some never speak language at all. Late language onset is a symptom

shared by most children with autism.

In an earlier study, the UCLA investigators studied the DNA of 291

families nationwide who had donated blood samples to the Los Angeles-

based Autism Genetic Resource Exchange. Each family had at least one

autistic child; youngsters who had never spoken were excluded. The

findings connected a specific region of Chromosome 7, called 7q35, to

autism.

In the current study, the researchers scrutinized every gene in the

7q35 region using DNA samples from 172 families. They identified four

promising genes; one of the candidates was CNTNAP2.

To verify their findings, the scientists conducted a second test on a

new group of 304 families. The CNTNAP2 gene showed up consistently,

confirming its implication in language development.

In a second approach, the researchers examined CNTNAP2's presence in

early brain tissue and discovered that the gene was most active in

developing brain structures involved in language and thought.

Postdoctoral fellow Brett Abrahams, who led this part of the

research, explains the finding's significance by comparing the brain

to a house.

" We know that different rooms in houses serve different purposes, "

said Abrahams. " For example, if an item only appears in the kitchen,

it makes sense to assume it's involved in cooking. Or if we find an

object only in the bedroom, it's likely connected to sleeping.

" The fact that we found CNTNAP2 concentrated in the brain's

structures that are involved in higher cognition gives us strong

clues about how its disruption might adversely shape brain

development, including speech and language, " he said.

In an unexpected third finding, the scientists found that statistical

evidence for the gene was strongest in families with autistic boys.

Less of an association appeared in families with autistic boys and

girls, or in families with autistic girls only.

" Autism strikes boys three times as often as girls, " said Maricela

Alarcon, first author and UCLA assistant professor in residence of

neurology. " This finding may partly explain why. "

The 3:1 gender ratio between boys and girls also applies to rates of

attention deficit disorders, learning disabilities and language

disorders.

" It will be interesting to learn whether CNTNAP2 also plays a role in

language development in non-autistic children, " observed

Alarcon. " Our next step will be to identify more traits, such as

seizures or other symptoms, that will help us track down additional

genes linked to the disorder. "

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