Stretches of DNA called retrotransposons, often dubbed “junk DNA,” might play an important role in schizophrenia. In a study published online on January 2, 2013 in the journal Neuron, a Japanese team revealed that LINE-1 retrotransposons are abnormally abundant in the schizophrenia brain, modify the expression of genes related to schizophrenia during brain development, and may be one of the causes of schizophrenia. Retrotransposons are short sequences of DNA that autonomously amplify and move around the genome. One class of retrotransposons named Long Interspersed Nuclear Elements (LINEs) make up a large part of the eukaryotic genome and it is believed that they may contribute to a number of disorders and diseases, such as cancer. LINE-1 retrotranspons have been shown to be more abundant in brain cells than in other cells in the body in adults, providing evidence for enhanced activity of LINE-1s in the human brain. However, the role played by LINE-1s in mental disorders, and in particular schizophrenia, has remained unclear. The team led by Dr. Kazuya Iwamoto from the University of Tokyo and Dr. Tadafumi Kato from the RIKEN Brain Science Institute demonstrated that the number of LINE-1 copies is elevated in the post-mortem brains of patients with schizophrenia. They show, using mouse and macaque models for schizophrenia and induced pluripotent stem (iPS) cells, that exposure to environmental risk factors during development, as well as the presence of genetic risk factors for schizophrenia, can lead to increased levels of LINE-1 copies in neurons. Employing whole genome analysis, the authors reveal that in schizophrenia patients LINE-1 reinserts into genes involved in synaptic function or schizophrenia and may result in disruptions in their normal functions.Login Or Register To Read Full Story