Interaction between catechol-O-methyltransferase (COMT) Val158Met genotype and genetic vulnerability to schizophrenia during explicit processing of aversive facial stimuli

Background. Emotion dysregulation is a key feature of schizophrenia, a brain disorder strongly associated with genetic risk and aberrant dopamine signalling. Dopamine is inactivated by catechol-O-methyltransferase (COMT), whose gene contains a functional polymorphism (COMT Val158Met) associated with differential activity of the enzyme and with brain physiology of emotion processing. The aim of the present study was to investigate whether genetic risk for schizophrenia and COMT Val158Met genotype interact on brain activity during implicit and explicit emotion processing. Method. A total of 25 patients with schizophrenia, 23 healthy siblings of patients and 24 comparison subjects genotyped for COMT Val158Met underwent functional magnetic resonance imaging during implicit and explicit processing of facial stimuli with negative emotional valence. Results. We found a main effect of diagnosis in the right amygdala, with decreased activity in patients and siblings compared with control subjects. Furthermore, a genotyperdiagnosis interaction was found in the left middle frontal gyrus, such that the effect of genetic risk for schizophrenia was evident in the context of the Val/Val genotype only, i.e. the phenotype of reduced activity was present especially in Val/Val patients and siblings. Finally, a complete inversion of the COMT effect between patients and healthy subjects was found in the left striatum during explicit processing. Conclusions. Overall, these results suggest complex interactions between genetically determined dopamine signalling and risk for schizophrenia on brain activity in the prefrontal cortex during emotion processing. On the other hand, the effects in the striatum may represent state-related epiphenomena of the disorder itself. Key words: COMT, emotion processing, genetic vulnerability, schizophrenia.