New Trigger Discovered for Fragile X Syndrome

A study that was published on July 5th, 2016 in the Journal of Neuroscience led by Yongjie Yang of Tufts University of Medicine identified an astrogial trigger mechanism as contributing to the symptoms of Fragile X Syndrome in mice subjects.

Fragile X Syndrome

Fragile X Syndrome or FXS is a genetic disorder which is caused from mutations in a gene on the X chromosome. It is the most common cause of inherited intellectual disability in humans and is associated with autism spectrum disorder. Previous studies had been related with the loss of a single protein, fragile X mental retardation protein (FMRP), as a predominant cause of Fragile X.

Astroglia, is a class of nervous system support cell, and they are abundant in the brain and help to regulate neuronal signaling. These cells are implicated in several neurological disorders, including FXS, but there is little known about how they become dysfunctional and contribute to disease.
Using mice that were genetically engineered, Yang and his team of colleagues selectively prevented astroglia from producing FMRP. They observed the animals developed symptoms similar to those seen FXS. The team identified an astrocyte-specific glutamate transporter, which when disrupted led to an imbalance of glutamate signaling, as a casual mechanism contributing to the symptoms of FXS. By restoring FMRP and glutamate signaling to astrocytes, the Yang lab saw a reversal of several FXS-like symptoms.

Senior study author Yongjie Yang said, “The involvement of vast number of glial cells, especially astroglial cells, is not well documented in neurodevelopmental disorders, such as Fragile X syndrome and autism. Our study, which used selective genetic manipulation of fragile X mental retardation gene in astroglial cells, found that one of the key functions of astroglial cells is impaired, which contributes to synaptic deficits. These results suggest a previously undescribed astroglial-mediated pathogenic mechanism in FXS, which may shed light on some types of autism. Indeed, we are currently investigating the alterations of glutamate transporter functions in other autism mouse models.”

Conclusion:

First study author Haruki Higashimori Ph.D., research assistant professor at Yang’s lab said, “The findings are exciting to me as a neuroscience researcher because they further our understanding of how FXS develops and might respond to a treatment.”
She further said, “By deepening our understanding of astroglia we may also gain insight into how our brains evolve and what role mutations play in that development process.”

Dr. Yang’s lab at Tuffs University School of Medicine is focused on learning how glia cells-astroglia in particular-develop and what causes these cells to become dysfunctional, causing conditions like Fragile X Syndrome, amyotropic lateral sclerosis (ALS) and autism.