The investigation of the catechol-O-methyltransferase (COMT-[rs4680]) and methylenetetrahydrofolate reductase (MTHFR-[rs1801133]) polymorphisms' interaction might shed light into the pathogenetic mechanisms of the cognitive dysfunction in schizophrenia.
To gain insight into the neural and molecular mechanisms of error processing, we used functional MRI to examine effects of a genetic variant in methylenetetrahydrofolate reductase (MTHFR 677C>T, rs1801133) that increases risk for schizophrenia and that has been specifically associated with increased perseverative errors among patients.
However, since our meta-analysis results demonstrated strong support for association of rs1801133 with schizophrenia, further replication studies based on a gene-wide approach need to be considered.
Among the Scandinavian patients the functional MTHFR SNP rs1801133 (C677T) significantly affected age at onset of schizophrenia in a dose-dependent manner (P = 0.0015), with lower age of onset with increasing numbers of the mutant T-allele.
A second polymorphism, methylenetetrahydrofolate reductase (MTHFR) 677C --> T (rs1801133), has been associated with overall schizophrenia risk and executive function impairment in patients, and may influence dopamine signaling through mechanisms upstream of COMT effects.