A major risk factor for schizophrenia is a genetic mutation called 22q11.2 microdeletion, which occurs in 1 of 4000 people. One third of people with this mutation develop schizophrenia or another psychotic disorder. Two groups shed light on the linkage between the mutated genes and the cognitive and physiological changes that may be involved in schizophrenia, in the November issue of Nature Neuroscience.
In one study, Doron Gothelf and colleagues administered psychological tests to children with and without 22q11.2 syndrome and examined them again several years later, in late adolescence or early adulthood. They found a strong effect of a particular mutation in the gene COMT, which produces a protein that breaks down the neurotransmitter dopamine. Subjects with this mutation had an abnormal decrease in the size of the prefrontal cortex (a brain region involved in reasoning and control), as well as lower IQs and more frequent psychotic symptoms than subjects without the mutation.
In the other study, Maria Karayiorgou and colleagues examined a mouse model of schizophrenia that contains a mutation in the gene for the enzyme proline dehydrogenase (PRODH), which breaks down the proposed neuromodulator proline. They report that this deficiency in PRODH alters the expression of the COMT gene. Interaction between these two genes modulated several schizophrenia-related phenotypes in these mice, such that COMT inhibition exaggerated or induced behavioral deficits in the PRODH-deficient mice. This synergistic interaction between these genes could explain the high disease risk associated with deletions in the 22q11.2 locus.
Doron Gothelf (Stanford University, CA, USA)
Maria Karayiorgou (The Rockefeller University, New York, NY, USA)
Abstracts available online: Paper 1; Paper 2
(C) Nature Neuroscience.
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