Autism has been declared a major national cause for 2012, and will have a high profile in France throughout the whole year. Paradoxically, this syndrome – and its causes in particular – remains poorly understood. A study published on February 9, 2012, in Public Library of Science – Genetics, shows that genetic mutations interfering with communication between neurons are directly involved in the disorder. These new findings confirm the neurobiological origins of autism spectrum disorders. They are the result of a collaboration between researchers from the Institut Pasteur, CNRS, Inserm, the Paris Public Hospital Network (AP-HP), with the University of Paris Diderot, the Robert Debré hospital (AP-HP), the Gillberg Neuropsychiatry Centre (Sweden), the University of Ulm (Germany), the French National Genotyping Center at the CEA, and the FondaMental foundation.
Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopment disorders, the genetic origins of which are not well understood. Mutations in over one hundred genes have previously been associated with ASDs, but it is difficult to assess their precise roles in neural function and to rank them in order of their relative importance. Genetic analyses conducted at the Institut Pasteur have shown new mutations in the SHANK2 gene, which can go as far as the complete loss of one of its copies in some patients. The SHANK2 gene encodes a protein located in the synapses, the points of contact that allow neurons to communicate with each other.
Researchers have shown that, in neuron cultures, mutations of the SHANK2 gene are linked to a reduction in the number of synapses and therefore to impaired neuronal communication. Furthermore, more detailed analysis on 3 patients missing one copy of the gene highlighted other chromosomal anomalies, which are rare, but which have already been linked to other neuropsychiatric disorders.
“All these results underline the vital importance of synaptic genes in autism spectrum disorders,” explained Professor Thomas Bourgeron, head of the Human Genetics and Cognitive Functions Unit at the Institut Pasteur-CNRS. “Furthermore, they point towards the existence of modifier genes that could modulate the symptoms of disorders collectively known as ASD.”
These results provide significant confirmation of the role of genetic mutations in the onset and development of autism. More in-depth analyses will be needed to give a more specific description of these impairments as well as their interactions.
BY: Anna Spyrou