Centers for Disease Control and Prevention estimates that Autism Spectrum Disorders affect 1 in 68 children in the United States. The rate of incidence appears to be increasing, but no one knows why. Because autism is a genetic disorder, current medical responses aim to mitigate symptoms rather than “cure” those afflicted. We can’t change our genes — yet.
Gene therapy is a hot research topic right now. But would it work for autism? An MIT study published this week in Nature offers promising results. The researchers used genetically engineered mice to test whether fixing a dysfunctional gene would reverse its effects, even in adulthood.
For their experiment, the scientists needed a mouse population they could manipulate with a “genetic switch.” They targeted the Shank3 gene, which produces autistic symptoms when inactive. (Autism can be caused by defects in many different genes; it varies by individual. Shank3 is one of the best-studied because it is a single gene, rather than a cluster. A defective Shank3 gene plays a role in about 1 percent of autism cases in humans.) Crossing two strains of lab mice produced a genetically engineered population in which the Shank3 gene was inoperable until exposed a certain chemical (tamoxifen). The mice were born with the gene not functioning. They exhibited autism-like symptoms (“anxiety, social interaction deficits, and repetitive behavior”). When the mice were adults, the scientists administered tamoxifen to restore normal function of the Shank3 gene. The mice showed significant improvement, both in brain function and in behavioral symptoms.
This study does NOT suggest that a magical cure for autism is imminent. The method used to “fix” the gene in these mice would not work in autistic humans. The scientists disabled the Shank3 gene in these particular mice using an artificial method that they could later reverse. What they demonstrated was that the adult brain maintains “some degree of plasticity"; it can repair itself. That means that if gene therapy does become available in the future, it will likely be an effective treatment in reversing some effects of autism in adults.