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National Fragile X Foundation
Fragile X Foundation
X Syndrome - GeneReviews
Fragile X syndrome is a type of mental retardation that affects children. Neuroscientists
studying the brains of adult patients have found that there are extra connections
in the Fragile X brain.
And as this ScienCentral News video reports, more is not a good thing.
Fragile X Syndrome
is a type of mental retardation that seems to affect boys more than girls.
“Patients with Fragile X Syndrome show a broad spectrum of cognitive
impairment,” says William
T. Greenough. “The effects are manifested in everything from language,
to motor skills. They are retarded; they are typically well behind in school;
and they are physically often very, very clumsy. There is also often a tendency
towards autistic behavior.” Greenough is a professor of psychology,
psychiatry, and cell and structural biology at the Beckman
Institute and the University
Since 1991, the scientific community has known that the malfunctioning of a
gene called FMR1
blocks the production of the Fragile X protein, and that this is somehow related
to Fragile X Syndrome. But according to Michael Tranfaglia, Medical Director
(a non-profit, family-run, Fragile X research foundation) it is still unclear
how the loss of this protein actually causes the specific symptoms of this
To see what is going on in the Fragile X brain, Greenough and his team studied
brain samples from deceased adult Fragile X sufferers and compared them to
brains from deceased normal adults. They found something abnormal about the
in the Fragile X brains. “Synapses are the points at which nerve cells,
communicate with one another.” Greenough explains. “Any time one
nerve cell sends a signal to another nerve cell, it does so through a synapse.”
Researchers were surprised to find that Fragile X patients had more synapses
than the unaffected individuals. Greenough says they also found that the synapses
were “misshapen, elongated, thin and abnormal.” He believes that
these extra, abnormal connections could be creating more “noise”
than normal signals in the brain.
Greenough explains that typically they would have expected more synapses or
connections to lead to “a more intelligent brain.” But in this
case, more is not better. They wondered why Fragile X patients had more synapses.
A normal vs. a Fragile X neuron image: Bill Greenough, Aaron Grossman
Greenough says that itâ€™s important to understand that normal brains produce
extra synapses to start with. That is, in early childhood the brain is programmed
to produce more synapses than it typically needs. But during development the
synapses that are used and have specific purposes are kept, while those that
aren't are pruned away, “so that you have fewer synapses in adulthood
than you had in childhood.”. The pruning process eliminates the extra
synapses or connections that are not serving any purpose, and thereby keeps
the brain efficient.
He and his team confirmed that the pruning process was defective in the case
of Fragile X patients. So synapses that should have been pruned were not.
Greenough also points out that the over-abundance of synapses actually distinguishes
Fragile X from other types of mental retardation in that, “almost all
other mental retardations actually involve brains that have fewer synapses.
In Fragile X, by contrast—by surprising contrast—there actually
are more synapses.”
There is currently no effective treatment for Fragile X Syndrome. Researchers
are hopeful that studies like Greenoughâ€™s may help them come closer
to testing drugs to treat, reverse or rehabilitate such abnormalities in the
The findings were part of a study presented at the 2003 American
Academy for the Advancement of Science meeting held in Denver. The study
was funded by grants from the National
Institute Of Child Health And Human Development, National
Institute Of Mental Health, FRAXA
Research Foundation, and the National
Alliance For Research On Schizophrenia And Depression (NARSAD).