Stanford University researchers have shown that a dysfunctional corpus callosum, responsible for communications between the brain’s two hemispheres, may cause some cases of autism, and they may be on track to discover the cause of autism spectrum disorder (ASD).
Making use of the human interactome—the full set of currently known interactions among human proteins—the researchers employed an algorithm to break it into smaller modules. When they overlaid these modules with a list of 383 proteins known to be encoded by ASD-associated genes, they found that one of them—number 13—included many more ASD-associated proteins than would be expected by chance.
They consulted the Allen Human Brain Atlas, a map of gene expression within the brain, which showed that half of the module 13 proteins were expressed throughout the brain but the other half were more specifically expressed in the corpus callosum. The corpus callosum is predominantly populated by cells that coat the signaling arms of neurons with an insulating layer of myelin, and is often smaller than average in individuals with ASD.
Past ASD research has mostly focused on neurons, but some of the proteins of module 13 are involved in the development of coating cells. Deficient myelination leads to problems in signal transfer between neurons, which may account for the symptoms of ASD.
The findings were “a bit surprising” according to Jingjing Li, one of the study’s authors, because compared with neurons, the coating cells “have not been extensively studied for their roles in autism.” The researchers, led by Stanford genetics professor Michael Snyder, acknowledge this to be a single step toward a more comprehensive goal: a systematic characterization of all the genetic changes that constitute ASD. “It’s a tough disease,” Li says.
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