Research into Dyslexia

For those rare individuals who enjoy reading research, I have found some nice bits and pieces:

Previous clinical studies have shown that up to 50 percent of children
of dyslexic parents have dyslexia themselves
.
These and other studies
of heritability led researchers to hunt for genes that influence the
disorder. In recent years, two other genes have also been linked to
dyslexia, EKN1 and KIAA0319. KIAA0319 is also involved in neuronal
migration.

The DCDC2 gene and its strong relationship to dyslexia have already been
replicated in an independent study in Germany **. “This is powerful
because those researchers studied subjects who speak a different
language and used different reading tests, yet they still found this
same gene involvement. This illustrates a strong role for human genetics
in the expression of the disorder,” says Dr. Gruen.

Although the disorder varies from person to person, common
characteristics among people with dyslexia include difficulty with
phonological processing (the manipulation of sounds) and/or rapid
visual-verbal responding
. Researchers estimate that 10 -17 percent of
the population in the U.S. has dyslexia. Dyslexia is also equally
prevalent in non-English-speaking countries. It is a common
misconception that dyslexia is simply a person who sees words backwards.
Only 30 percent of dyslexics have trouble with reversing letters and
numbers.

“Traditionally, many people are under the impression that dyslexia is
an issue with visualizing letters differently. However, we now know that
dyslexics just learn to read differently – most learn to read by sight
memorization not phonetically,”
says Dr. Gruen.. Anatomically,
dyslexics have normal brains; however, the brain areas activated in
reading may be different. Several studies using fMRI, an imaging
technique that studies activity in the brain, have shown that dyslexics
display different patterns of brain activity than other people when they
read.

“Some kids just learn differently. Not all children learn to read with
our current one-size fits all methods,” says Dr. Gruen. “The
earlier we can identify children at risk, the earlier we can start
intervention when studies have shown that remediation works best. Even
with the future capabilities of genetic testing for dyslexia, the
biggest problem is still the lack of infrastructure for early
intervention in schools.”

Dr. Gruen cautions that although we can now draw a path from the disease
to the gene, the reverse is not necessarily proven yet. That is,
predicting the outcome for a person who has the gene and determining if
the person will have the disorder is still not possible. The next steps
of the research will examine other variations including deletions or
changes in this particular gene family. The investigators will also
examine brain imaging in children and adults given reading tasks and
then see how that relates to DCDC2 variations. Ultimately, identifying
dyslexia genes may provide opportunities for early identification of the
disorder and help to distinguish dyslexia from other learning
disabilities.

The NINDS is a component of the National Institutes of Health (NIH) in
Bethesda, Maryland , and is the nation’s primary supporter of
biomedical research on the brain and nervous system. The NIH is
comprised of 27 Institutes and Centers and is a component of the U. S.
Department of Health and Human Services. It is the primary Federal
agency for conducting and supporting basic, clinical, and translational
medical research, and investigates the causes, treatments, and cures for
both common and rare diseases. For more information about NIH and its
programs, visit http://www.nih.gov/.

*Meng H, Smith S, Hager K, Held M, Liu J, Olson R, Pennington B, DeFries
J, Gelernter J, O’Reilly-Pol T, Somlo S, Skudlarski P, Shaywitz S,
Shaywitz B, Marchione K, Wang Y, Murugan P, LoTurco J, Grier P, Gruen J.
“DCDC2 is associated with reading disability and modulates neuronal
development in the brain.” Proceedings of the National Academy of
Sciences, November 22, 2005, Vol.102, pp.17053-17058.

**Schumacher J, Anthoni H, Dahdouh F, Konig I, Hillmer A, Kluck N,
Manthey M, Plume E, Warnke A, Remschmidt H, Hulsmann J, Cichon S,
Lindgren C, Propping P, Zuccheli M, Ziegler A, Peyrard-Janvid M,
Schulte-Korne G, Nothen M, Kere J. “Strong genetic evidence of DCDC2
as a susceptibility gene for dyslexia.” The American Journal of Human
Genetics, January 2006, Vol. 78, pp.52 – 62.

-By Michelle D. Jones-London, Ph.D.

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