Association of the IFN-γ (+874A/T) Genetic Polymorphism with Paranoid Schizophrenia in Tunisian Population

ABSTRACT

Since growing evidence suggests a significant role of chronic low-grade inflammation in the physiopathology of schizophrenia, we have hypothesized that functional genetic variant of the IFN gamma (IFN-γ; +874A/T; rs2430561) gene may be involved in the predisposition to schizophrenia. This research is based on a case–control study which aims to identify whether polymorphism of the IFN-γ gene is a risk factor for the development of schizophrenia. The RFLP-PCR genotyping of the IFN-γ gene was conducted on a Tunisian population composed of 218 patients and 162 controls. The IFN-γ (+874A/T) polymorphism analysis showed higher frequencies of minor homozygous genotype (TT) and allele (T) in all patients compared with controls (11.5 vs. 4.9%; p = 0.03, OR = 2.64 and 30.7 vs. 24.1%, p = 0.04, OR = 1.4, respectively). This correlation was confirmed for male but not for female patients. Also, the T allele was significantly more common among patients with paranoid schizophrenia when compared with controls (25.8 vs. 4.9%, p = 0.0001; OR = 6.7). Using the binary regression analysis to eliminate confounding factors as age and sex, only this last association remained significant (p = 0.03; OR = 1.76, CI = 1.05–2.93). In conclusion, our results showed a significant association between +874A/T polymorphism of IFN-γ and paranoid schizophrenia, suggesting that this single nucleotide polymorphism (SNP) or another at proximity could predispose to paranoid schizophrenia. Since the minor allele of this polymorphism was correlated with an increased expression of their product, our study validates the hypothesis of excessive pro-inflammatory cytokine in the physiopathology of paranoid schizophrenia.

KEYWORDS:

• Behavioral disorders
• genetic polymorphism
• IFN-γ
• paranoid subtype
• proinflammatory cytokine
• schizophrenia

Acknowledgments

We thank the staff of the Department of Psychiatry of the CHU F Bourguiba of Monastir for providing samples and clinical information. We are grateful to Sarra CHAHED for her assistance with the linguistic part of this paper.

Declaration of interest

None of the authors has any potential financial conflict of interest related to this manuscript. The authors alone are responsible for the content and writing of the paper.

Funding

This work was supported by the Ministry of Higher Education, Scientific Research and Technology of Tunisia.