New clue found for Fragile X syndrome-epilepsy link

April 12, 2011, Emory University
Kv4.2, which regulates electrical signals, is lower in cells from mice missing FMRP ("KO") compared to wild-type ("WT"). Credit: Christina Gross

Individuals with fragile X syndrome, the most common inherited form of intellectual disability, often develop epilepsy, but so far the underlying causes are unknown. Researchers have now discovered a potential mechanism that may contribute to the link between epilepsy and fragile X syndrome.

The protein that is missing in fragile X syndrome, FMRP, controls the production of a protein that regulates electrical signals in brain cells, scientists at Emory University School of Medicine have found. The results were published April 13 in the Journal of Neuroscience.

Individuals with fragile X syndrome tend to have a hyperexcitable , which can be displayed in several ways: hyperactivity, anxiety, increased sensory sensitivity, and epileptic seizures in 20 percent of all cases. The Emory team's findings suggest that a therapeutic strategy against fragile X syndrome now being tested in clinical trials could also address this aspect of the disease.

"The link between fragile X syndrome and was not well understood," says senior author Gary Bassell, PhD, professor of cell biology and neurology at Emory University School of Medicine. "This finding might provide a molecular explanation that could also give some clues on therapeutic strategies."

The co-first authors of the paper are postdoctoral fellow Christina Gross and PhD candidate Xiaodi Yao. They and their colleagues found that in mice missing FMRP – a model for humans with fragile X syndrome – brain cells produce less of a protein called Kv4.2.

FMRP is known to regulate several genes, and it's possible that changes in others besides Kv4.2 contribute to the development of epilepsy. For many of the genes that FMRP controls, it normally acts as a brake, by interfering with the step in which RNA is made into protein. In FMRP's absence, this leads to runaway protein production at synapses the junctions between where chemical communication occurs. Kv4.2 appears to be an exception, because in FMRP's absence, less Kv4.2 protein is produced.

The protein Kv4.2 is an ion channel, which allows electrical charge to flow out of neurons when they are stimulated. Kv4.2 is the major ion channel regulating the excitability of neurons in the hippocampus, a region of the brain important for learning and memory. A mutation of the gene encoding Kv4.2 leads to temporal lobe epilepsy in humans.

In laboratory tests, drugs that tamp down glutamate signaling could partially restore levels of the Kv4.2 protein in mice missing the fragile X protein. This suggests that drugs that act against glutamate signaling, which are now in clinical trials, could reduce hyperexcitability in humans with fragile X syndrome.

Another strategy could be to identify drugs that target the Kv4.2 protein's function directly, Bassell says.

Not all individuals with fragile X syndrome develop epilepsy. The loss of FMRP doesn't shut Kv4.2 production off completely, and other genetic variations and environmental factors probably contribute to the development of epilepsy in individuals with , Bassell says.

More information: C. Gross, X. Yao, D.L. Pong, A. Jeromin and G.J. Bassell. Fragile X Mental Retardation Protein Regulates Protein Expression and mRNA Translation of the Potassium Channel Kv4.2. J. Neurosci, 31

Related Stories

Recommended for you

Breakthrough article on mechanistic features of microRNA targeting and activity

March 23, 2018
Giovanna Brancati and Helge Grosshans from the FMI have described target specialization of miRNAs of the let-7 family. They identified target site features that determine specificity, and revealed that specificity can be ...

Calorie restriction trial in humans suggests benefits for age-related disease

March 22, 2018
One of the first studies to explore the effects of calorie restriction on humans showed that cutting caloric intake by 15% for 2 years slowed aging and metabolism and protected against age-related disease. The study, which ...

Boosting enzyme may help improve blood flow, fitness in elderly

March 22, 2018
As people age, their blood-vessel density and blood flow decrease, which is why it's harder to maintain muscle mass after 40 and endurance in the later decades, even with exercise. This vascular decline is also one of the ...

Scientists pinpoint cause of vascular aging in mice

March 22, 2018
We are as old as our arteries, the adage goes, so could reversing the aging of blood vessels hold the key to restoring youthful vitality?

Sulfur amino acid restriction diet triggers new blood vessel formation in mice

March 22, 2018
Putting mice on a diet containing low amounts of the essential amino acid methionine triggered the formation of new blood vessels in skeletal muscle, according to a new study from Harvard T.H. Chan School of Public Health. ...

Cold can activate body's 'good' fat at a cellular level, study finds

March 21, 2018
Lower temperatures can activate the body's 'good' fat formation at a cellular level, a new study led by academics at The University of Nottingham has found.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.