Genetic analysis of nitric oxide synthase 1 variants in schizophrenia and bipolar disorder

Abstract

Nitric oxide (NO) is a neurotransmitter that acts as a second messenger of the N-methyl-D-aspartate receptor and interacts with the dopaminergic and the serotonergic systems. NO involvement in pathological processes relevant to neuropsychiatric disorders stems from its ability to modulate certain forms of synaptic plasticity, and from its capacity to be transformed to a highly active free radical. Additionally, multiple links have been reported between the NO-producing enzyme, nitric oxide synthase (NOS) 1, and both schizophrenia and bipolar disorder (BPD). RNA and DNA isolated from dorsolateral-prefrontal cortices of schizophrenia patients, bipolar patients and controls (n = 26, 30 and 29, respectively) were donated by the Stanley Foundation Brain Collection. Gene expression was measured by Real-Time-PCR. Genetic polymorphisms were genotyped by restriction-fragment length-polymorphism analysis, and by product-size determination of PCR products amplified with a fluorescent primer.Expression analysis of pan-NOS1, as well as of 2 of its isoforms, "NOS1_1d" and "NOS1_1f", which differ in their first exons and translational strength, revealed a trend for pan-NOS1 over-expression (P = 0.075) in schizophrenia patients (1.33-fold), and significant over-expression (P < 0.05) of NOS1_1d and NOS1_1f in this group (1.54-fold and 1.61-fold, respectively). No expressional alteration was observed in BPD. Polymorphisms at the promoters of NOS1_1d and NOS1_1f, previously shown to be functional in vitro, revealed no significant allelic or genotypic differences among clinical groups and showed no effect on these transcripts' expression. In conclusion, understanding the molecular mechanisms underlying the over-expression of specific NOS1 isoforms, which is unique to schizophrenia, may assist in identifying targets for new drugs.

The genetic contribution of the NO system at the glutamatergic post-synapse to schizophrenia: Further evidence and meta-analysis

“…In contrast to our results, a study by Silberberg et al (2010) did not detect any changes in NOS1 expression in rs41279104 carriers. Importantly, in the study by Silberberg et al (2010) samples from both healthy and schizophrenic subjects were used, with increased NOS1 expression in patients with schizophrenia, regardless of genotype.…”

“…Therefore, it is possible that in the Silberberg et al (2010) study increased NOS1 expression in schizophrenic patients is masking a possible reduction in NOS1 expression caused by rs41279104. Alternatively, this might be due to a mere power problem, inherent to this kind of studies where only a few risk allele carriers can be tested and overall sample size is limited.…”

“…Titles and abstracts were scrutinized to exclude non-genetic studies, reducing the number of included studies to Costain et al, 2010;Fang et al, 2008;Greenwood et al, 2011;Husted et al, 2010;Kremeyer et al, 2009;Miranda et al, 2006;Nicodemus et al, 2008;Wratten et al, 2009) and one on NOS1 (Fallin et al, 2005), presented family-based, but not case-control data and were therefore not integrated in the meta-analysis for methodological reasons. The remaining studies on NOS1AP (n=6; (Aberg et al, 2010;Delorme et al, 2010;Nicodemus et al, 2010;Puri et al, 2007;Puri et al, 2006;Zheng et al, 2005)) and NOS1 (n=14; (Cui et al, 2010;Donohoe et al, 2009;Kawohl et al, 2008;Nicodemus et al, 2010;O'Donoghue et al, 2012;Okumura et al, 2009;Reif et al, 2006;Reif et al, 2011;Riley et al, 2010;Rose et al, 2012;Shinkai et al, 2002;Silberberg et al, 2010;Tang et al, 2008;Wang et al, 2012)) reported on case-control association data and were scrutinized in greater detailed. For NOS1AP, two and for NOS1, 11 further studies had to be excluded from meta-analysis for the following reasons.…”

“…For the NOS1 gene: (Kawohl et al, 2008;O'Donoghue et al, 2012;Rose et al, 2012) analysed exclusively healthy participants. (Donohoe et al, 2009;Nicodemus et al, 2010;Riley et al, 2010) and (Shinkai et al, 2002) only presented data on SNPs which have not been genotyped for the present study; no SNP data could be obtained from the study of (Wang et al, 2012); and the study by (Silberberg et al, 2010) was excluded because of the rather small sample size (n=26) precluding meaningful interpretation of the data. Finally, (Reif et al, 2011) and (Reif et al, 2006), were excluded because the case samples of both studies overlapped with the sample described here (while the control sample was extended more than two-fold).…”

“…Importantly, in the study by Silberberg et al (2010) samples from both healthy and schizophrenic subjects were used, with increased NOS1 expression in patients with schizophrenia, regardless of genotype. In contrast, samples analyzed in our study were only obtained from healthy subjects.…”