What causes
AS? Is it genetic?
Twin and family studies suggest there is a genetic vulnerability to AS
and the other ASDs, but a specific gene for AS hasn’t been identified.
It is likely that multiple genes cause AS, since the symptoms and the
severity of symptoms vary so widely among individuals.
Researchers recently identified an association between certain
behavioral traits (the insistence on strict routines and repetitive
behavior) in a group of children with autism and a specific gene –
GABRB3. Another study discovered a strong association between autism and
the mutation of a gene the researchers call ENGRAILED 2. Additional
evidence for the link between inheritable genetic mutations and AS is
seen in the higher incidence of family members of children with an ASD
who have similar behavioral symptoms, but in a more limited form. For
example they may have mild social, language, or reading problems.
Current research points to structural abnormalities in the brain as a
cause of AS. These abnormalities impact neural circuits that control
thought and behavior. Researchers think that gene/environment
interactions cause some genes to turn on or turn off, or turn on too
much or too little in the wrong places, and this interferes with the
normal migration and wiring of embryonic brain cells during early
development.
Researchers at the University of California , supported in part by the
National Institutes of Health, have proposed the disorder stems from
abnormal changes that happen during critical stages of fetal
development. Defects in the genes that control and regulate normal brain
growth create abnormal growth patterns, which cause overgrowth in some
brain structures and reduced growth, or excessive cell loss, in others.
Using advanced brain imaging techniques, scientists have revealed
structural and functional differences in specific brain regions between
the brains of normal versus AS children. One study found a lack of
activity in the frontal lobe of AS children when asked to respond to
tasks that required them to use their judgment. Another found
differences in brain activity when children were asked to respond to
facial expressions. Other methods of investigating brain function have
revealed abnormal levels of particular proteins in the brains of adults
with AS, which correlate with obsessive and repetitive behaviors.
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Last Updated 9/2/2007