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Autism is
a major cause of mental retardation, affecting 10 to 20 of every 10,000
people, and more males than females. Features of classical autism include
impaired social interaction, poor verbal and nonverbal communication,
and unusual or limited activities and interests. In addition, people with
autism often respond abnormally to sounds, touch, or other sensory stimulation.
Symptoms usually appear during the first three years of childhood and
continue through life. There have been several recent studies suggesting
that some people have a genetic predisposition to autism.
Further understanding of the disease
Several avenues of
research at Baylor College of Medicine are aimed at determining genetic
alterations that may cause or increase susceptibility to autism. Researchers
hypothesize that such alterations are not passed from previous generations
in nuclear DNA (deoxyribonucleic acid), but rather occur as new variations
in sperm, eggs, or early embryonic cells. These so-called "epigenetic"
alterations generally involve chemical modification of the DNA (such as
the addition of methyl groups) without alteration of the underlying nucleotide
sequence. It is possible that certain DNA sequences may be prone to epigenetic
alteration, or that nutrition could affect epigenetic stability. Several
genes have been identified as candidates for possible involvement in autism
and are being studied further. The possibility that folic acid intake
might also affect the epigenetic risk for autism is also being investigated.
Animal studies at Baylor College of Medicine allow more detailed study
of genes that are thought to be involved in autism. In these systems it
is possible to monitor the products of such genes and other cellular components
with which they interact. For instance, a gene involved in control of
symmetry in the development of the fruit fly eye may be related to a gene
in humans that is associated with susceptibility to autism. Researchers
hope that studying these animal genes and what they do might provide some
clues as to what is happening during the development of normal and autistic
brains. Useful information about autism may also come from studies of
a mouse model of Rett syndrome, whose symptoms include a component of
autism. Another group of mouse models under study contain alterations
in genes that are involved in the epigenetic regulation of DNA expression,
and that also exhibit behavioral differences that may relate to the hyperactivity
seen in autism.
Another line of research that relates to autism is study of the Reelin
protein and its involvement in vertebrate brain development, since Reelin
has been implicated in numerous human diseases that affect the brain.
Work towards therapy
With a better knowledge of epigenetic alterations, brain development,
and the function of genes that may be involved in the occurrence of autistic
symptoms, researchers hope to find avenues that lead to therapy for autism.
Baylor investigators
working on Autism:
Baylor MRDDRC projects associated with Autism:
Organizations:
Disease information:
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