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    Clues to Schizophrenia's Origins Uncovered

    Analysis found gene variant prompts too much 'pruning' in brain during teen years

    WebMD News from HealthDay

    By Dennis Thompson

    HealthDay Reporter

    WEDNESDAY, Jan. 27, 2016 (HealthDay News) -- Some people might develop schizophrenia when a normal process of brain development goes haywire in adolescence and early adulthood, Harvard researchers report.

    Everyone undergoes what is called "synaptic pruning" as they move into adulthood, explained study author Steven McCarroll, director of genetics for the Broad Institute's Stanley Center for Psychiatric Research and an associate professor of genetics at Harvard Medical School in Boston.

    It's how extra brain cells and synapses (the junctions where nerve signals cross from one brain cell to the next) are eliminated in the cerebral cortex, to increase the efficiency of function, he said.

    But a gene that contributes to synaptic pruning may increase a person's risk of schizophrenia if certain mutations cause things to go wrong, McCarroll and his colleagues explained.

    "Somehow, this biological process becomes miscalibrated and removes too many synapses," McCarroll said. "Something about this process of maturation, if it goes awry, results in brain wiring that can no longer perform some of the basic functions that it used to be able to perform."

    The findings were published online Jan. 27 in the journal Nature.

    About 1 percent of U.S. adults have schizophrenia, and about seven or eight people out of every 1,000 will have schizophrenia in their lifetime, according to the U.S. National Institute of Mental Health (NIMH).

    People with schizophrenia may hear voices or see things that aren't there, or develop irrational delusions of grandeur or persecution, according to NIMH. Patients might also display disorganized thinking, agitated body movements or emotional withdrawal. Symptoms most frequently appear in patients when they are teenagers or young adults.

    The gene implicated in this study, C4, normally acts as a regulator of the immune system, McCarroll said. The gene helps target debris, viruses and other pathogens for destruction by immune cells.

    Earlier research had linked the C4 gene to schizophrenia, leading some to believe the mental disorder might be caused by some sort of virus or infection, he said.

    However, the research team learned that the C4 gene also "moonlights" in synaptic pruning, playing a role in the process by tagging synapses for elimination, McCarroll said.

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