Risk genes for schizophrenia and autism conspicuously activate in the same neuronal neighborhood of the brain’s cortex, or outer mantel, during infancy. This suggests some related underlying illness processes – even though known genetic variations associated with the disorders overlap by only 5 percent, say researchers.
Their study, which pinpointed the developmental trajectories of the suspect genes in the monkey brain, also identified divergent timing of risk gene activation that might help to explain the differing courses of the illnesses. Autism-related genes first switched on in newborn neurons during prenatal development, while schizophrenia risk genes didn’t activate until infancy.
This suggests that genetic risk for autism may have more to do with prenatal processes, such as the birth of new neurons, while schizophrenia risk genes may impact processes underway during infancy, such as refinement of neuronal circuitry. The delay is consistent with schizophrenia’s much later onset of symptoms in late adolescence/early adulthood, the researchers note.