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Gene linked to families with more than one autistic child
A version of a gene has been linked to autism in families that have more than one child with the
disorder. Inheriting two copies of this version more than doubled a child’s risk of developing an
autism spectrum disorder, scientists supported by the National Institutes of Health’s (NIH)
National Institute of Mental Health (NIMH) National Institute on Child Health and Human
Development (NICHD) have discovered.
In a large sample totaling 1,231 cases, they traced the connection to a tiny variation in the part of
the gene that turns it on and off. People with autism spectrum disorders were more likely than
others to have inherited this version, which cuts gene expression by half, likely impairing
development of parts of the brain implicated in the disorder, report doctors online during the
week of the October 16, 2006 in the Proceedings of the National Academy of Sciences.
A version of a gene has been linked to autism in families that have more than one child with the
disorder. Inheriting two copies of this version more than doubled a child’s risk of developing an
autism spectrum disorder, scientists supported by the National Institutes of Health’s (NIH)
National Institute of Mental Health (NIMH) National Institute on Child Health and Human
Development (NICHD) have discovered.
In a large sample totaling 1,231 cases, they traced the connection to a tiny variation in the part of
the gene that turns it on and off. People with autism spectrum disorders were more likely than
others to have inherited this version, which cuts gene expression by half, likely impairing
development of parts of the brain implicated in the disorder, report doctors online during the
week of the October 16, 2006 in the Proceedings of the National Academy of Sciences.
| Autism |
To explore this possible connection, the researchers looked for associations between the
brain disorder and nine markers in the MET gene, sites where letters in the genetic code
vary among individuals. They tested two samples: the first, 204 families, including 26
with more than one child with autism spectrum disorders, the second, 539 families,
including 452 with such multiple affected children.
One marker, the C version, emerged as over-transmitted at “highly significant” levels in
people with autism spectrum disorders in both samples. Moreover, this association held
only for families with more than one affected child and was strongest in a sub-sample of
those with more narrowly-defined autism. The C version was significantly less prevalent
in a group of 189 unrelated controls than in the individuals with autism or their parents.
“Since autism likely involves complex interactions between many different genes and
other factors, common genetic predisposing factors are likely more influential in families
with multiple affected members. Some cases in families with only one affected member
more likely stem from rarer genetic glitches or other sporadic events”explained one
doctor.
brain disorder and nine markers in the MET gene, sites where letters in the genetic code
vary among individuals. They tested two samples: the first, 204 families, including 26
with more than one child with autism spectrum disorders, the second, 539 families,
including 452 with such multiple affected children.
One marker, the C version, emerged as over-transmitted at “highly significant” levels in
people with autism spectrum disorders in both samples. Moreover, this association held
only for families with more than one affected child and was strongest in a sub-sample of
those with more narrowly-defined autism. The C version was significantly less prevalent
in a group of 189 unrelated controls than in the individuals with autism or their parents.
“Since autism likely involves complex interactions between many different genes and
other factors, common genetic predisposing factors are likely more influential in families
with multiple affected members. Some cases in families with only one affected member
more likely stem from rarer genetic glitches or other sporadic events”explained one
doctor.
The researchers propose that in some individuals with autism spectrum disorders who also develop digestive and immune
system or non-specific neurological problems, the MET gene variant might play a role in impairing both brain and peripheral
organ development.
“We know that autism is the most heritable of neuropsychiatric disorders, but, thus far, we have not identified genes that
consistently are associated with this developmental brain disease. This new finding is an important clue, which if replicated
in an independent sample, will take us closer to understanding the genetic basis of autism.” said NIMH Director.
system or non-specific neurological problems, the MET gene variant might play a role in impairing both brain and peripheral
organ development.
“We know that autism is the most heritable of neuropsychiatric disorders, but, thus far, we have not identified genes that
consistently are associated with this developmental brain disease. This new finding is an important clue, which if replicated
in an independent sample, will take us closer to understanding the genetic basis of autism.” said NIMH Director.
| For more details visit: http://www.nih.gov |
Autism is one of the most heritable mental disorders. If one identical twin has it, so will the other in nearly 9 out of 10 cases.
If one sibling has the disorder, the other siblings run a 35-fold greater-than-normal risk of having it. Still, scientists have so
far had only mixed success in identifying the genes involved.
While most previous studies had focused on genes expressed in the brain, this team of doctors saw a clue in the fact that
some people with autism also have gastrointestinal, immunological or neurological symptoms in addition to behavioral
impairments. They focused on a gene that affects such peripheral functions as well as the development of the cortex and
cerebellum, brain areas disturbed in autism. Moreover, it is located in a suspect area of chromosome 7 that has been
previously linked to autism spectrum disorders.
If one sibling has the disorder, the other siblings run a 35-fold greater-than-normal risk of having it. Still, scientists have so
far had only mixed success in identifying the genes involved.
While most previous studies had focused on genes expressed in the brain, this team of doctors saw a clue in the fact that
some people with autism also have gastrointestinal, immunological or neurological symptoms in addition to behavioral
impairments. They focused on a gene that affects such peripheral functions as well as the development of the cortex and
cerebellum, brain areas disturbed in autism. Moreover, it is located in a suspect area of chromosome 7 that has been
previously linked to autism spectrum disorders.
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