Association of the Met-196-Arg Variation of Human Tumor Necrosis Factor Receptor 2 (TNFR2) with Paranoid Schizophrenia

Research has provided strong evidence for oligodendrocyte and myelin-related genes dysfunction in schizophrenia. Several studies have suggested abnormalities in the expression of myelin-related genes including tumor necrosis factor receptor 2 (TNFR2) involved in the neurodegeneration and remyelination. In order to further assess the role of TNFR2 in schizophrenia, we examined a functional bi-allelic polymorphism associated with an impaired NF-KB signaling and cell survival. In the present case/control study, 220 patients with schizophrenia and 176 healthy controls were genotyped by RFLP-PCR for the T/G polymorphism at the position 676 in exon 6 of the TNFR2 gene. We found a trend towards over-representation of TNFR2 676G in the patients compared to the controls ( p = 0.19 and 0.09 respectively). Interestingly, when we evaluated the association between this genetic polymorphism and the clinical variables of schizophrenia, our findings indicated that the frequencies of the G/G genotype and the G allele were significantly higher in paranoid ( p = 0.014 and p = 0.012 respectively) and adult-onset paranoid ( p = 0.004 and p = 0.004 respectively) schizophrenia patient group compared to the controls. The potential association was confirmed by a logistic regression model only for development of the paranoid form of schizophrenia ( p = 0.022) indicating a substantially increased risk for paranoid schizophrenia with inheritance of the TNFR2(G) allele. In conclusion, this polymorphism in TNFR2 or a gene in proximity seems to be associated specifically with paranoid schizophrenia, at least in the Tunisian population. A replication of our findings in other and larger populations could be of particular importance to establish TNFR2 as one of the susceptibility genes of paranoid schizophrenia.