Generally marked by hallucinations, delusions, and disorganized thinking, schizophrenia, which affects 1% of adults, has a strong genetic component. It has long been discussed whether this component is determined by rare changes in DNA that have a major impact on the organism or a series of more frequent changes, each of which contributes a little to the overall effect. Two recent studies have provided evidence for both of these phenomena, which can affect the same biological processes and lead to a person developing the disease. In the first, a group led by Vassily Trubetskoy of Charité University Hospital in Berlin, Germany, analyzed the genomes of 76,755 people with schizophrenia and 243,649 without. The researchers found 342 variants that may increase the risk of the disease, although each contributes by less than 5%. Using a combination of techniques, they found 120 genes most likely to cause schizophrenia (Nature, April 8). In the second study, led by Benjamin Neale and Mark Daly of the Broad Institute, USA, the exomes (a region of the genome that produces proteins) of 24,248 individuals with schizophrenia and 97,322 without were sequenced. The data showed extremely rare changes in 10 genes that increase the risk of a person having the disease by up to 50 times (Nature, April 8).
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