A new piece to the autism puzzle
Most cases of autism are not caused by a single genetic mutation. However, several disorders with autism-like symptoms, including the rare Fragile X syndrome, can be traced to a specific mutation. Several years ago, MIT neuroscientist Mark Bear discovered that this mutation leads to overproduction of proteins found in brain synapses — the connections between neurons that allow them to communicate with each other.In a paper published today in Nature, Bear and colleagues have now shown that tuberous sclerosis, another rare disease characterized by autism and mental retardation, is caused by the opposite malfunction — too little synthesis of those synaptic proteins. Though the findings might seem counterintuitive, they fit into the theory that autism can be caused by a wide range of brain-synapse glitches, Bear says. “The general concept is that appropriate brain function occurs within a very narrow physiological range that is tightly maintained,” he says. “If you...