Researchers have reverse-engineered the outlines of a disrupted prenatal gene network in schizophrenia, by tracing spontaneous mutations to where and when they likely cause damage in the brain. Some people with the brain disorder may suffer from impaired birth of new neurons in the front of their brain during prenatal development, suggest the researchers, who compared spontaneous mutations in 105 affected and 84 unaffected siblings, in families without previous histories of the illness.