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NUTLEY, N.J.—A team researchers from Roche and the Biozentrum of the University of Basel recently discovered a specific dysfunction in neuronal circuits, one that is caused by autism and the reversal of which might represent a treatment for the condition. A paper on the study, "Shared Synaptic Pathophysiology in Syndromic and Non-syndromic Rodent Models of Autism," appeared in the Oct. 5 issue of Science.
The study focused on the neuroligin-3 gene. Neuroligins are proteins responsible for mediating the formation of synapses between neurons and specifying the functions of those synapses. Alterations or mutations in the genes that encode neuroligins are associated with autism as well as other cognitive disorders, and neuroligin-3 is one of the over 300 candidate genes in which mutations are implicated with a risk for developing autism.
"Neuroligin-3 is involved in the formation of synapses, the contact junctions between nerve cells. In studies using neuroligin-3 knockout mice we have now identified a defect in synaptic signal transmission that interferes with the function and plasticity of neuronal circuits," Peter Scheiffele, professor at the University of Basel Biozentrum and lead investigator of the study, said in a press release. "These negative effects are associated with increased production of a specific glutamate receptor, mGlu1, which modulates signal transmission between neurons. An excess of these receptors inhibits the adaptation of synaptic signal transmission during the learning process, thus disrupting the development and function of the brain in the long term."
After the researchers reactivated neuroligin-3 in the mouse models, the nerve cells were shown to decrease the production of mGlu1 to regular levels, and as a result, the structural defects that present in autistic brains disappeared.
The findings have applicability in conditions other than autism, as the paper's abstract notes that many monogenic syndromes such as fragile X syndrome, of which autism is a symptom, "have revealed specific defects in synaptic plasticity."
"These findings represent a significant step in enabling the identification of medicines for autism and highlight the pivotal role of public–private partnerships in advancing our understanding of this complex disease." Luca Santarelli, head of Neuroscience Research at Roche, said in a press release. "These results are of major importance because they support the notion that, although many genes are involved in autism, there is a convergence at the level of the synapse which can be targeted for therapeutics."
Moving forward, in EU-AIMS, a project supported by the European Union, research groups from the Biozentrum and Roche are collaborating with industry partners to examine the potential of glutamate receptor antagonists as a treatment for autism.
There is currently no cure for autism, and treatment for the disorder is limited to alleviating the symptoms by way of behavioral therapy and other treatments.
Autism is a neurological developmental disorder that presents in early childhood. Autism and autism spectrum disorder are characterized by difficulties with social interaction, verbal/nonverbal communication and repetitive behaviors. Intellectual disability, difficulties in motor coordination and attention and physical health issues are also common, according to the Autism Speaks website. The U.S. Centers for Disease Control and Prevention (CDC) state that one in 88 American children fall somewhere in the autism spectrum, with roughly one in 54 boys and one in 252 girls diagnosed with the condition. More than two million people are affected by autism spectrum disorders (ASDs) in the United States alone, with tens of millions affected worldwide, notes Autism Speaks. The economic burden is considerable, with the CDC noting that "intensive behavioral interventions for children with ASDs cost $40,000 to $60,000 per child per year."
In addition to Scheiffele, the paper's authors include Stephane J. Baudouin, Julien Gaudias, Stefan Gerharz, Laetitia Hatstatt, Pradeep Punnakkal and Kaspar Vogt of the Biozentrum of the University of Basel; Kuikui Zhou and Chris I. De Zeeuw of the Department of Neuroscience, Erasmus MC; and Kenji F. Tanaka and Rene Hen of the Department of Neuroscience at Columbia University.