Researchers at Brown University have discovered a structure in the brain called the Fragile X granule, which offers a potential target for treating certain kinds of autism and mental retardation.
Led by Justin Fallon, professor of neuroscience at Brown, the study's finding opens a new line of research about potential treatments for autism.
Austism is a neurological disorder that strikes young children and can impair development of social interaction and communication.
"If you are going to treat the disease you need to be able to target the defective elements. The Fragile X granule offers such a target," said Fallon.
Although, autism can be caused by a variety of genetic factors, Fallon's lab focused on one particular area - the Fragile X protein.
If that protein is mutated, it leads to Fragile X syndrome, which causes mental retardation and is often accompanied by autism.
It is believed that autism and mental retardation are diseases of the synapse, the basic unit of information exchange and storage in the brain.
The researchers focused their study on the Fragile X protein and synaptic connections in healthy mice.
By examining specially prepared sections of mouse brain tissue with high-powered light and electron microscopes, researchers made a number of determinations.
First, they showed that Fragile X exists at the pre-synaptic, or sending side of the synapse, an area that had not been widely studied.
"For over 25 years the field has focused almost exclusively on the post-synaptic, receiving side. Almost no one has looked at the pre-synaptic side, as it was not thought to be involved in Fragile X," said Fallon.
This discovery is important because scientists, if they are to treat Fragile X syndrome, autism or mental retardation must know where the functional defect actually is. Fallon's research helps fill in a potential gap.
"The implication is that pre-synaptic defects could contribute to the pathology in autism in Fragile X," said Fallon.
Also, researchers found that Fragile X protein is only present in a small fraction of what are known as pre-synaptic specializations.
The pre-synaptic Fragile X protein also turned out to be present in microscopic granules, which look like tiny pebbles under a high-powered microscope. Understanding the Fragile X granule is important in this context because the finding could lead to more targeted treatments.
The researchers hypothesize that the granules contain multiple RNAs, or sets of genetic information to help modify the synapse during learning and memory.
If their theory is proven correct, the granules might serve as pinpoint targets for eventual drug treatments of autism.
The study, titled "The FXG: A presynaptic Fragile X granule expressed in a subset of developing brain circuits," is published in the recent issue of the Journal of Neuroscience.