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See if the genetic component of sporadic schizophrenia can be explained by de novo mutations that result in altered proteins.

Exomes of cases and control family trios (offspring and parents) were sequenced and compared to identify mutations present only in the offspring. The cases consisted of 53 individuals diagnosed with sporadic schizophrenia or schizoaffective disorder and their unaffected parents. The control group consisted of 22 healthy individuals and their parents. There was no family history of mental illness in either cohort.

There was no difference in the mutation rate in the offspring of individuals with schizophrenia and those without, but the effect of mutations differed. Individuals with schizophrenia had more mutations in genes that affected protein function. 34 point mutations and four INDels were identified in the individuals with schizophrenia, of which 32 were shown to affect protein coding. These mutations were not present in the exomes of any of the unaffected parents or those analysed as part of the 1000 genomes project. In contrast, only four of the seven mutations identified in the control group affected protein coding. Additional analysis showed that all the mutations occurred in different genes and only one had previously been associated with schizophrenia.

The genetic basis of sporadic schizophrenia can be explained by the occurrence of multiple de novo mutations that affect protein coding. The large numbers of genes that may be mutated explain why this disease is prevalent around the globe.

Schizophrenia is a complex disease and this study gives us some explanation of its genetic basis. The findings in this study are similar to a previous study published in the same journal which also implicates de novo mutations in schizophrenia (see previous news).