To determine if the overexpression of miR negatively
To determine if the overexpression of miR-137 negatively regulate EFNB2 expression, human neuroblastoma SH-SY5Y cells were transfected with mature miR-137 sequences or negative control miRNAs. The results showed that the overexpression of miR-137 did not affect the mRNA expression of EFNB2 but significantly repressed the accumulation of EFNB2 protein. This post-transcriptional function was consistent with initial discovery of animal miRNA, which inhibited protein synthesis and preserved the stability of the mRNA target (Ambros, 2004; Olsen and Ambros, 1999; Seggerson et al., 2002). Similarly, we demonstrated that in the peripheral blood of first-onset schizophrenia patients compared with healthy controls, the expression of miR-137 was significantly increased, and the mRNA levels of EFNB2 were not significantly different.
We used the conventional ROC curve of miR-137 in peripheral blood to calculate the area under the curve (AUC) with 95% confidence intervals. The AUC reached 0.795, indicating that miR-137 has certain value for diagnosing schizophrenia. Schizophrenia is a chronic, frequently disabling mental disorder with neurodevelopmental impairment (Insel, 2010). In both the neurodevelopment and the etiology of psychiatric disease such as schizophrenia, miRNA plays a pivotal role (Miller and Wahlestedt, 2010; Welberg, 2010; Xu et al., 2010). Because daunorubicin tissue is not readily accessible, blood-based expression profiling of miRNAs is increasingly common for the discovery of pathophysiology and identification of potential biomarkers for schizophrenia (Lai et al., 2011; Yu et al., 2015; Zhang et al., 2014). A major advantage of blood sample is avoiding potential changes in miRNA levels by different processing conditions (Cheng et al., 2013). The current study also showed that miR-137 in peripheral blood is a potential biomarker for differentiating between schizophrenia patients and healthy controls.
It is important to note that although the rare SNP rs550067317 in EFNB2 gene was not genotyped in a large population and the frequency of the minor allele C in the patients of schizophrenia and healthy controls was unknown, but we uncovered that it is a functional genetic variant through point mutation and dual luciferase activity assay. The other limitation of the current study is that TaqMan method for quantifying gene expression might be more sensitive than SYBR. However, the latter is widely accepted and applied to many studies.
Conclusion We provided strong experimental evidence that miR-137 directly down-regulates the expression of EFNB2, and a genetic variant in the RNA binding site in EFNB2 gene affects the expression regulation. MiR-137, as a risk factor for schizophrenia, might be implicated in NMDA receptor signaling and/or Reelin signaling pathway. Further clinical experiment in peripheral blood verified that miR-137 is aberrantly expressed in the first-onset patients of schizophrenia compared healthy controls and it has certain diagnostic value for the disease. This study not only improved the understanding of the roles of EFNB2 and the genetic basis of rs550067317 for schizophrenia, but also provided new evidences for miR-137 involved in schizophrenia etiology and diagnosis, which might contribute to discover new biomarkers and therapeutic targets for the disease.
Conflicts of Interest
Acknowledgments We are indebted to all of the individuals who have participated in, or helped with, our research. This study was supported by the National Natural Science Foundation of China (No. 81301151; 31371298), the China Postdoctoral Science Foundation (No. 2013M542337; 2015T81016), and the Program for New Century Excellent Talents in University (NCET-13-0452).
Introduction In a recent Global Burden of Disease Study, ‘acute’ schizophrenia received the highest disability weight out of 220 health state valuations (0–76, where 0 equals no disability and 1 equals complete disability) (Salomon et al., 2012). Recent meta-analyses using magnetic resonance imaging (MRI) show that schizophrenia is characterized by reductions in gray matter, which occur before full symptom onset and progress more quickly in the acute exacerbation state (Olabi et al., 2011) and treatment-resistant state, compared with the treatment-responsive state (Mouchlianitis et al., 2016). For example, Takahashi et al. (2010) reported that first-episode schizophrenia and schizotypal patients showed significant decreases in gray matter volume in the left transverse temporal gyrus and left planum temporale approximately 2–7years after an initial assessment, compared with control samples. Although the precise neurobiological mechanisms underlying progressive deterioration in the left transverse temporal gyrus and left planum temporale in schizophrenia are unknown, a growing body of work has implicated abnormal excitatory amino acid neurotransmission, possibly mediated by a deficit in recurrent inhibition (Coyle and Konopaske, 2016). Although controversial, this mechanism could elicit ongoing, use-dependent cellular damage mediated via excitotoxic effects. In in vivo studies, increased glutamate levels appear to feature early in the course of illness, rather than during chronic schizophrenia (Marsman et al., 2013). However, glutamate production and toxicity may play a role in the acute state of schizophrenia.