Promise for autism cure
doi:10.1038/nindia.2010.74 Published online 7 June 2010
Neuroscientists have identified previously unknown defects in an area of the brain involved in the debilitating emotional symptoms of Fragile X Syndrome (FXS) — the leading genetic cause of autism and mental retardation. These defects are synaptic — pertaining to the a structure that permits a neuron to pass an electrical or chemical signal to another cell.
The study could have important therapeutic significance since the researchers have been able to correct some of these defects through pharmacological treatment in genetically engineered mice with FXS. If the experiment can be successfully replicated in humans, thousands of autistic and mentally retarded individuals might find a cure.
Sumantra Chattarji and colleagues from the National Centre for Biological Sciences in Bangalore along with researchers at New York University have unravelled these defects and their probable cures opening doors for promising autism treatment protocols.
FXS is caused by a mutation in a gene on the X chromosome. Individuals with FSX suffer from a wide range of problems, such as learning disabilities, attention deficit, seizures, anxiety and mood instability, probably involving several regions of the brain. The researchers interested in the cellular and molecular basis for the emotional problems associated with FXS studied how neurons and synapses in the amygdala—a small, almond-shaped part of the brain known to mediate emotion's influence on memory—are affected in mice with FXS.
The team found defects on both sides of synapses in the amygdala through electrophysiological recordings. They reported that the neurons were not properly communicating with each other. They identified the molecular correlates of these defects pinpointing exactly where the breakdown occurs.
"Together, these deficits impair the ability of neurons to communicate and encode information", Chattarji says.
Chattarji and his team then started pondering on how to normalise communication between neurons. They focused on group I metabotropic glutmate receptors (mGluRs), known to be involved in synaptic dysfunction in other brain areas in FXS. They were able to reverse some of the deficits by treatimg amygdala neurons with a drug that blocked these receptors. When the receptors were blocked, some communication between neurons was restored.
The novelty of the study is that it elucidates the cellular and synaptic deficits in the amygdala whereas most earlier studies focused on brain defects underlying cognitive deficits of FXS.
- Suvrathan, A. et al. Characterization and reversal of synaptic defects in the amygdala in a mouse model of fragile X syndrome. P. Natl. Acad. Sci. USA. doi: 10.1073/pnas.1002262107 (2010)