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. 2019 Nov 18;46(3):612–622. doi: 10.1093/schbul/sbz114

A Network Analysis of Epigenetic and Transcriptional Regulation in a Neurodevelopmental Rat Model of Schizophrenia With Implications for Translational Research

Yang Du 1, Xue-Song Li 2, Lei Chen 1, Guang-Yang Chen 2, Yong Cheng 1,3,✉
PMCID: PMC7147587  PMID: 31738422

Abstract

Prenatal administration of mitotoxin methylazoxymethanol acetate (MAM) in rats produces behavioral, pharmacological, and anatomical abnormalities once offspring reach adulthood, thus establishing a widely used neurodevelopmental model of schizophrenia. However, the molecular aspects underlying this disease model are not well understood. Therefore, this study examines epigenetic and transcriptional dysregulation in the prefrontal cortex and hippocampus of MAM rats as these are brain regions closely associated with schizophrenia pathogenesis. Upon sequencing messenger and microRNA (mRNA and miRNA, respectively), differential expression was revealed in the prefrontal cortex and hippocampus between MAM- and saline-treated rats; sequencing data were validated by qualitative real-time polymerase chain reaction. Bioinformatic analyses demonstrated that the differentially expressed (DE) genes were strongly enriched in interactive pathways related to schizophrenia, including chemical synaptic transmission, cognition, and inflammatory responses; also, the potential target genes of the DE miRNAs were enriched in pathways related to synapses and inflammation. The blood of schizophrenia patients and healthy controls was further analyzed for several top DE mRNAs: DOPA decarboxylase, ret proto-oncogene, Fc receptor-like 2, interferon lambda receptor 1, and myxovirus (influenza virus) resistance 2. The results demonstrated that the expression of these genes was dysregulated in patients with schizophrenia; combining these mRNAs sufficiently differentiated schizophrenia patients from controls. Taken together, this study suggests that the MAM model has the potential to reproduce hippocampus and prefrontal cortex abnormalities, relevant to schizophrenia, at the epigenetic and transcriptional levels. These data also provide novel targets for schizophrenia diagnoses and treatments.

Keywords: methylazoxymethanol acetate, mRNA, miRNA, prefrontal cortex, hippocampus

Introduction

Schizophrenia is a severe mental disease that affects approximately 1% of the population worldwide.1,2 Multiple brain region abnormalities are thought to be involved in schizophrenia pathogenesis; the most implicated regions are the prefrontal cortex3 and hippocampus.4 Although the etiology of schizophrenia is still poorly understood, it is generally accepted that the disease starts early in life with neurodevelopmental abnormalities,5 and psychosis usually develops during late adolescence or early adulthood.1 Therefore, utilizing neurodevelopmental models of schizophrenia to investigate disease pathophysiology and facilitate novel drug discovery has attracted great interest over the last several decades.

Exposing pregnant rats to methylazoxymethanol acetate (MAM) on gestational day 17 selectively disrupts the mitosis of neural precursor cells, leading to abnormal neurodevelopment in their offspring.6 Once the offspring reach adulthood, they show anatomical alterations in the brain resembling phenomena seen in postmortem brains with schizophrenia, including parvalbumin dysregulation in the hippocampus and frontal cortex.7 Adult MAM-treated rats also exhibit behavioral problems, including sensorimotor gating deficits, reduced social interaction, and cognitive dysfunction.7,8 In addition, these rats show increased dopamine neuron population activity and enhanced sensitivity to psychostimulants.9,10 Due to the characteristics of MAM-treated rats, the MAM-E17 rat model has been widely used as a neurodevelopmental of schizophrenia.

Although the anatomical, pharmacological, and behavioral characteristics of MAM-treated rats have been well addressed, studies on the potential molecular mechanisms underlying the MAM-17 rat model are limited. Therefore, in this study, microRNA and messenger RNA sequencing (miRNA-seq and mRNA-seq, respectively) were performed in the prefrontal cortex and hippocampus of MAM- and saline-treated rats to analyze epigenetic and transcriptional regulation in the model. In addition, bioinformatics and gene network analyses were conducted to explore the functional involvement of epigenetic and transcriptional dysregulation in the disease model. Finally, representative molecular components of the disease model were assessed for their potential with translational research in schizophrenia patients.

Methods

Animals and Samples

Pregnant female Sprague Dawley rats were purchased from Vital River. The MAM animal model of schizophrenia was obtained from Moore et al.11 Rats were intraperitoneally injected with a single dose of 20 mg/kg MAM (Wako) or saline on gestational day 17 accordingly. The animals were housed at 24 ± 1ºC and 50 ± 1% humidity under a 12-h light/dark cycle (lights on from 9 am to 9 pm) and provided ad libitum access to a standard diet and drinking water. Their offspring were sacrificed at 8 weeks of age; then, whole blood samples were collected and the hippocampus and prefrontal cortex of the MAM- and saline-treated rats were dissected. Samples were stored at −80ºC until use. All animal experiments were conducted in full compliance with the National Institutes of Health Laboratory Animal Care and Use Guidelines (NIH Publication No. 80-23) and were approved by the Animal Care and Use Committee of Minzu University of China.

Human Participants and Sample Collection

Schizophrenia patients diagnosed via the Structured Clinical Interview for DSM-IV and International Classification of Diseases 10 were recruited from the Third People’s Hospital of Foshan, Guangdong, China; schizophrenia patients with medical illnesses were excluded. In addition, healthy people were recruited as controls through advertisements; the demographic and clinical characteristics of the participants are shown in supplementary table S1. All schizophrenia patients and controls provided written, informed consent and the study protocol was approved by the ethics committee at The Third People’s Hospital of Foshan, Guangdong, China. Experiments were conducted in accordance with the Declaration of Helsinki.

miRNA and mRNA Library Construction and Sequencing

Total RNA samples were extracted from the prefrontal cortex and hippocampus of 6 male MAM-treated and 6 male saline-treated rats using the Trizol method according to the manufacturer’s protocol (Thermo Fisher Scientific). Library construction and sequencing for both miRNA and mRNA were performed as previously described.12,13

Differential Expression Analysis

Transcripts per million miRNA values >1 and mRNA values for fragments per kilobase of transcript per million mapped reads >10 were selected across all samples for differential expression analysis between MAM- and saline-treated rats using edgeR14; outliers, defined as data points that did not fall within 2 SDs of the mean, were excluded from the analysis. Significantly differentially expressed (DE) miRNAs and mRNAs were reported at P < .05.

Metascape Analysis for DE miRNA and mRNA Target Genes

Metascape pathway enrichment analysis15 was used for DE mRNAs and miRNA target genes. The TargetScan database (version 6.2) was used to predict DE miRNA target genes and the threshold of TargetScan context+ scores was set as −0.20.

Quantitative Real-time Polymerase Chain Reaction

Total RNA was extracted from the whole blood, hippocampus, and prefrontal cortex of MAM- and saline-treated rats and the whole blood of schizophrenia patients and normal controls using the Trizol method according to the manufacturer’s protocol (Thermo Fisher Scientific). Next, quantitative real-time polymerase chain reaction (qRT-PCR) was performed as previously described.12 The cycling conditions were: 10 min preincubation at 95°C, 35 cycles of deoxyribonucleic acid synthesis at 95°C for 15 s, 59°C for 15 s, and 72°C for 30 s. Primer sequences are shown in supplementary table S2. The potential of mRNA levels to differentiate schizophrenia patients from normal controls was assessed by a receiver operating characteristic (ROC) curve. The area under curve (AUC) indicates the accuracy with which a particular mRNA can differentiate patients and controls. AUC values above 50% suggest a particular mRNA can possibly differentiate between patients and controls and an AUC value of 100% indicates it can perfectly differentiate between cases and controls. ROC curve and Pearson’s correlation analyses were achieved by SPSS 22.0 statistical analysis software. The Student’s t-test was used for statistical analyses to compare 2 groups, and statistical analyses for comparing multiple groups were achieved by 1-way analysis of variance, followed by a Tukey’s multiple comparison test. Statistical significance levels were set at *P < .05, **P < .01, and ***P < .001.

Results

Bioinformatics Analysis of DE mRNAs in the Hippocampus and Prefrontal Cortex

The hippocampi and prefrontal cortices were analyzed from MAM- and saline-treated male rats by mRNA-seq, resulting in the identification of thousands of mRNAs. The analysis showed that 705 mRNAs in the hippocampus (figure 1A) and 1430 mRNAs in the prefrontal cortex (figure 1B) had significant expression changes between MAM- and saline-treated rats. Of the DE mRNAs in the hippocampus, 377 were upregulated and 328 were downregulated. In the prefrontal cortex, 728 mRNAs were upregulated and 702 were downregulated. Moreover, the transcriptional expression of 213 genes was significantly altered in both the hippocampus and prefrontal cortex of MAM-treated rats (supplementary figure S1A and supplementary table S3).

Fig. 1.

Fig. 1.

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Bioinformatics analysis of DE mRNAs. Heatmaps show cluster analysis data for 705 DE mRNAs in the hippocampus (A) and 1430 DE mRNAs in the prefrontal cortex (B). A Metascape bubble map for viewing the top 20 enrichment clusters in the hippocampus (C) and prefrontal cortex (D) is shown, and a unique square code represents a specific cluster. Metascape enrichment network analysis data depicting the intracluster and intercluster similarities of enriched terms for the hippocampus (E) and prefrontal cortex (F), up to 10 terms per cluster, are shown. DE, differentially expressed; mRNA, messenger RNA, MAM, methylazoxymethanol acetate.

To understand the molecular mechanisms underlying the disease model, a Metascape enrichment analysis was performed for the DE genes in the hippocampus and prefrontal cortex. The bioinformatic analyses showed that the top 5 Metascape enrichment pathways for the affected hippocampal genes include chemical synaptic transmission, cognition and antigen processing, and the presentation of peptide antigen via major histocompatibility complex class I (figure 1C). Additionally, the most significant Metascape enrichment cluster for the prefrontal cortex-affected genes is behavior; the other top 5 Metascape enrichment pathways include cognition and chemical synaptic transmission (figure 1D). Next, Metascape was used to form enrichment networks to analyze intracluster and intercluster relatedness for the top 20 enrichment clusters in the hippocampus (figure 1E) and prefrontal cortex (figure 1F). The analyses suggested that high intracluster similarities drove the formation of tight local complexes and a substantial proportion of clusters were bridged through subterms with similarities. Notably, Metascape also allows the submission of multiple gene lists to facilitate the understanding of shared pathways; findings based on the input of the 2 DE gene lists suggested that most of the top 20 Metascape enrichment clusters involved the DE genes in both the hippocampus and prefrontal cortex, whereas the rest only involved the DE genes in the prefrontal cortex (supplementary figure S1B).

Bioinformatics Analysis of DE miRNAs in the Hippocampus and Prefrontal Cortex

The analysis of the hippocampi and prefrontal cortices from MAM- and saline-treated male rats by miRNA-seq resulted in the identification of thousands of miRNAs. The expression of 10 miRNAs in the hippocampus (figure 2A and supplementary table S4) and 37 in the prefrontal cortex (figure 2B and supplementary table S4) were found to be significantly changed in MAM-treated rats compared with saline-treated rats. Of the 10 DE miRNAs in the hippocampus, 4 were downregulated and 6 were upregulated. Of the 37 miRNAs in the prefrontal cortex, 11 were downregulated and 26 were upregulated. Next, TargetScan was used to predict the mRNA targets of the MAM-associated miRNAs in the hippocampus and prefrontal cortex. Metascape bioinformatics analysis results indicated that the top enriched pathways for the predicted targets of various DE miRNAs were related to inflammation, synaptic transmission, and neuronal differentiation (figure 2C).

Fig. 2.

Fig. 2.

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Bioinformatics analysis of DE miRNAs. Heatmaps showing cluster analysis data of 10 DE miRNAs in the hippocampus (A) and 37 miRNAs in the prefrontal cortex (B). (C) The top 3 Metascape enrichment pathways for predicted target genes of DE miRNAs are shown. DE, differentially expressed; miRNA, microRNA; MAM, methylazoxymethanol acetate.

Interactive Analysis of Epigenetic and Transcriptional Regulation in a MAM Rat Model

To systematically understand the functional involvement of epigenetic and transcriptional dysregulation in the disease model, we bioinformatically predicted the gene targets of the DE miRNAs in MAM rats and selected genes that have been validated by mRNA-seq. This identified a number of genes that were negatively regulated by multiple miRNAs in both the hippocampus (supplementary figure S2A) and prefrontal cortex (supplementary figure S2B). A Metascape enrichment analysis was also performed for these validated target genes. The top 3 enriched pathways for the genes were cytokine signaling in the immune system; response to growth factor and interferon signaling in the hippocampus (figure 3A); and cellular response to organic cyclic compound, learning or memory, and regulation of lipid biosynthetic process (figure 3B).

Fig. 3.

Fig. 3.

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Interactive analysis of DE miRNAs and mRNAs. The top 20 Metascape enrichment pathways of validated DE miRNA target genes in the hippocampus (A) and prefrontal cortex (B) are shown. DE, differentially expressed; miRNA, microRNA; mRNA, messenger ribonucleic acid.

qRT-PCR Validation of DE mRNAs in the Hippocampus, Prefrontal Cortex, and Blood

Next, qRT-PCR was performed to validate the mRNA-seq data and chose genes that were highly dysregulated in both the hippocampus and prefrontal cortex of MAM-treated rats (figure 4A). Metascape enrichment analysis suggests that the selected 11 genes were enriched in pathways related to an inflammatory response (supplementary figure S3A). The dysregulated transcriptional expression of these 11 genes in the hippocampus and prefrontal cortex of male MAM-treated rats was validated by qRT-PCR except that RT1 class Ib, locus S3 (RT1-S3), and RT1 class I, locus T24, gene 4 (RT1-T24-4) mRNA levels in the prefrontal cortex were not significantly different between male MAM- and saline-treated rats (figure 4B and supplementary fig. S3B–L).

Fig. 4.

Fig. 4.

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Validation of qRT-PCR data for DE mRNAs in the hippocampus, prefrontal cortex, and blood between MAM- and saline-treated rats. (A) The 11 DE mRNAs were selected for validation. Note that gene function descriptions were acquired from the National Center for Biotechnology Information’s Gene database.30 (B) Fcrl2, Rps2-ps2, Rpl3, RT1-N2, Ifnlr1, Ret, DDC, Rexo4, RT1-S3, RT1-T24-4, and Mx2 expression in the hippocampus and prefrontal cortex between MAM- and saline-treated rats is shown. (C) Blood DDC, Ifnlr1, Ret, Fcrl2, and Mx2 expression between MAM- and saline-treated rats (4 males and 3 females for each group) is shown. MAM, methylazoxymethanol acetate; qRT-PCR, quantitative reverse transcription-polymerase chain reaction; DE, differentially expressed; mRNA, messenger RNA, DDC, DOPA decarboxylase; Ret, ret proto-oncogene; Fcrl2, Fc receptor-like 2; Ifnlr1, interferon lambda receptor 1; Rexo4, RNA exonuclease 4; Mx2, myxovirus (influenza virus) resistance 2; Rps2-ps2, ribosomal protein S2; Rpl3, ribosomal protein L3; NA, not applicable. Data are expressed as the mean ± SE. *P < .05, **P < .01, ***P < .001.

To investigate whether there is a sex difference for DE mRNAs in the MAM model of schizophrenia, transcriptional expression of these 11 genes in the hippocampus and prefrontal cortex of female MAM- and saline-treated rats was evaluated. Data from qRT-PCR showed that female and male MAM-treated rats had similar dysregulation patterns for the 11 selected genes, although there were no statistically significant differences between female MAM- and saline-treated rats for interferon lambda receptor 1 (Ifnlr1) and RNA exonuclease 4 (Rexo4) mRNA levels in the hippocampus and for Rexo4 and myxovirus (influenza virus) resistance 2 (Mx2) mRNA levels in the prefrontal cortex (figure 4B and supplementary figure S3B–L).

DE mRNA Levels in the Blood of MAM-Treated Rats

Next, blood samples were collected from MAM- and saline-treated rats to analyze several molecular components found in disease model brains. Results from qRT-PCR showed that the mRNA expression of DOPA decarboxylase (DDC), ret proto-oncogene (Ret), and Fc receptor-like 2 (Fcrl2) were upregulated and mRNA expression of Mx2 was downregulated in the peripheral blood of MAM-treated rats (figure 4C); these changes are consistent with the data from the brains of MAM-treated rats. However, Ifnlr1 mRNA levels were significantly increased in the peripheral blood of MAM-treated rats when compared with saline-treated rats (figure 4C); this was inconsistent with the data from the brains of MAM-treated rats.

mRNA-seq Implications in Translational Research

To assess the utility of data from the neurodevelopmental model of schizophrenia for clinical research, blood samples were collected from schizophrenia patients and healthy controls and evaluated for the 5 mRNAs that were dysregulated in the blood of the disease model. The results showed that DDC mRNA levels were significantly increased in first-episode, drug-free schizophrenia patients but not in chronically medicated patients (figure 5A). In contrast, Ifnlr1 and Ret mRNA levels were significantly increased in both first-episode, drug-free and chronically medicated patients with schizophrenia when compared with controls (figure 5B, C). In addition, Fcrl2 and Mx2 mRNA levels were significantly decreased in both first-episode, drug-free and chronic medicated schizophrenia patients (figure 5D, E).

Fig. 5.

Fig. 5.

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Implications of MAM rat model data in translational research. Data from qRT-PCR analyses of DDC (A), Ifnlr1 (B), Ret (C), Fcrl2 (D), and Mx2 (E) blood mRNA levels between 68 FEDF schizophrenia patients, 72 CT schizophrenia patients, and 72 HCs are shown. (F) Pearson’s correlation coefficients (and P values in parentheses) between disease status, age, sex, disease severity, and the aforementioned 5 genes are shown. (G) ROC curves were utilized to evaluate the accuracy of the 5 mRNAs in the blood for potentially differentiating between FEDF patients and HCs. (H) ROC curves were used to assess the accuracy of the 5 mRNAs in the blood to potentially differentiate between total patients and HCs. qRT-PCR, quantitative reverse transcription-polymerase chain reaction; FEDF, first-episode, drug free; CT, chronically treated; DDC, DOPA decarboxylase; Ret, ret proto-oncogene; Fcrl2, Fc receptor-like 2; Ifnlr1, interferon lambda receptor 1; Mx2, myxovirus (influenza virus) resistance 2; HC, healthy control; ROC, receiver operating characteristic; PANSS, Positive and Negative Syndrome Scale; GADPH, glyceraldehyde 3-phosphate dehydrogenase; MAM, methylazoxymethanol acetate. Data are expressed as the mean ± SD.

Additional analyses were performed on blood DDC, Ifnlr1, Ret, Fcl2, and Mx2 mRNA levels in male and female schizophrenia patients. The analyses showed that male and female schizophrenia patients had comparable dysregulated expression patterns for DDC, Ifnlr1, Ret, Fcl2, and Mx2 in their blood (supplementary figure S4), suggesting that sex is unlikely to be a confounding factor. Pearson’s correlation analysis was utilized to investigate whether age, sex, or disease severity affected the transcriptional expression levels of these 5 genes in schizophrenia patients. There were significant correlations between Positive and Negative Syndrome Scale total scores, positive scores and DDC mRNA levels, and positive scores and Fcrl2 mRNA levels in patients (figure 5F).

Given the significant differences between schizophrenia patients and controls for blood DDC, Ifnlr1, Ret, Fcrl2, and Mx2 mRNA levels, it was necessary to explore their potential as biomarkers for a schizophrenia diagnosis. The ROC-AUC analysis suggested that these mRNAs could moderately differentiate between first-episode, drug-free schizophrenia patients and controls; also, combining the 5 mRNAs increased diagnostic accuracy (figure 5G). Furthermore, Ifnlr1, Ret, Fcrl2, and Mx2, but not DDC, moderately differentiated between total schizophrenia patients and controls (figure 5H). These results indicate that the 5 mRNAs have the potential to be schizophrenia biomarkers. Additionally, an ROC-AUC analysis suggested that sex differences do not affect the accuracy of the 5 mRNAs in differentiating between schizophrenia patients and controls (supplementary figure S5).

Discussion

This genome-wide, integrative analysis of 2 molecular profiling platforms provides novel insights into the role of epigenetic and transcriptional dysregulation in the pathophysiology of MAM-E17 rats, a neurodevelopmental model of schizophrenia. In both the hippocampus and prefrontal cortex of MAM-E17 rats, DE miRNA and mRNA were present during late adolescence or early adulthood. Bioinformatic analyses of the DE mRNAs in MAM-treated rats revealed that the top enriched pathways for these genes include cognition, behavior, chemical synaptic transmission, synapse organization, and ion transport regulation; a number of implicated pathways for the target genes of the DE miRNAs are related to synapses. Many of the DE mRNAs and miRNAs in the prefrontal cortex and hippocampus appear to be components of functional interaction networks. Interestingly, the top 5 enrichment pathways for the DE mRNAs in the hippocampus and prefrontal cortex both include cognition and chemical synaptic transmission. These findings are consistent with previous studies suggesting that impaired cognition in schizophrenia patients and animal models are associated with dysregulated connectivity between the hippocampus and prefrontal cortex during working memory processing.16,17 Therefore, the neurodevelopmental model of schizophrenia has the potential to reproduce hippocampus and prefrontal cortex abnormalities relevant to schizophrenia pathogenesis at the epigenetic and transcriptional levels.

Another set of molecular components that were strongly disrupted in the brains of MAM-treated rats is associated with the inflammatory response. Previously, studies have shown neuroinflammation in the brains of patients with schizophrenia,18,19 as well as dysregulated inflammatory cytokine expression in the cerebral cortex of schizophrenia patients.20 Although neuroinflammation marker findings in postmortem brain samples from patients with schizophrenia were inconsistent across studies, a systematic review suggested that microglia activity, serpin family A member 3, and interferon-induced transmembrane levels were consistently increased in postmortem brains of schizophrenia patients.21 The important role of the inflammatory response in pathogenesis was further supported by clinical trials showing the beneficial effects of anti-inflammatory drugs on schizophrenia patients.22–24 In addition, the antioxidant N-acetylcysteine, which also exhibits anti-inflammatory properties, has been shown to improve neurocognitive impairments in early psychosis schizophrenia patients.25 However, the direct evaluation of molecular components underlying neuroinflammatory responses in schizophrenia patients at the time of psychosis is inherently difficult. In this study, gene expression screening of a rat model of schizophrenia identified several novel inflammatory-related genes that were strongly dysregulated in the prefrontal cortex and hippocampus. These genes include Fcrl2, Ifnlr1, and Mx2; these have not been linked to neuropsychiatric diseases in the literature. Also, an analysis of DDC, Ret, Fcrl2, Ifnlr1, and Mx2 mRNA expression in the blood of MAM-treated rats revealed that DDC, Ret, Fcrl2, and Mx2 mRNA expression abnormalities in MAM-treated rats were consistent in the brains and peripheral blood, supporting the “peripheral as a window to the brain” hypothesis.26 However, the mechanism underlying the inconsistent results regarding Ifnlr1 mRNA expression between the central and peripheral blood of MAM-treated rats is unclear. Nevertheless, future studies are necessary to understand the potential roles of these genes in the onset and/or development of schizophrenia and may provide novel targets for schizophrenia treatment.

In further research on the pathophysiology of the disease model at the “omics” level, Hradetzky et al used proteomics and metabolomics to investigate the potential underlying molecular pathways affected in MAM-E17 rats and found 38 DE proteins in the hippocampus.10 Bioinformatics analysis of 38 proteins indicated that the most affected canonical pathways were related to calcium signaling and synaptic and glutamatergic neurotransmission10; these findings are consistent with the present data. However, the proteomics and metabolomics study did not find DE proteins in the frontal cortex between MAM- and saline-treated rats; this is in direct contrast to the large number of DE mRNAs in the prefrontal cortex found in the present study. One explanation for the discrepancy is the subfield-specific gene expression in the model. Another possibility is that the methodology utilized by Hradetzky et al was not sensitive enough to detect protein changes in the frontal cortex of MAM-treated rats as suggested by the authors. In addition, Hradetzky et al used 3-month-old animals for their study, whereas the animals used in this study were 8-week old and were considered to be in late adolescence or early adulthood.

The potential translational implications of the molecular changes identified in the prefrontal cortex and hippocampus of MAM-treated rats were analyzed by gene expression in the blood of schizophrenia patients. Consistent with data from the animal model of schizophrenia, qRT-PCR results showed that blood DDC mRNA levels were significantly increased in first-onset, drug-free schizophrenia patients when compared with controls whereas long-term treatment with antipsychotics reduced blood DDC mRNA levels in patients. These results were reasonable given that it is well known that antipsychotics target the dopamine system to alleviate schizophrenia symptoms.27,28 In fact, DDC activity was reported to be elevated in the brains of patients with schizophrenia at the time of psychosis.29 The present data also reveal that the expression of 3 inflammatory response-related genes, Fcrl2, Ifnlr1, and Mx2, were dysregulated in patients with schizophrenia; antipsychotics did not significantly affect the expression of these genes. Moreover, of the 5 genes analyzed in schizophrenia patients and the disease model, blood DDC, Ret, Ifnlr1, and Mx2 mRNA expression showed consistent dysregulation between the schizophrenia patients and the disease model, thus confirming the MAM model as a useful tool for translational schizophrenia research. Therefore, these genes may provide novel targets for schizophrenia treatment, though future studies are necessary to investigate the expression of these genes in the brains of patients with schizophrenia. Additionally, ROC-AUC curve analysis showed that combining these mRNAs could suitably differentiate between schizophrenia patients and controls, suggesting that the representative molecular components found in the neurodevelopment model of schizophrenia have the potential to guide schizophrenia diagnoses.

In conclusion, the present mRNA-seq and miRNA-seq data provide a framework for evaluating the molecular mechanisms underlying the pathophysiology of the neurodevelopmental model of schizophrenia at the transcriptional and epigenetic levels and offer rich data sets of DE miRNAs and mRNAs in the brains of MAM rats for further study. Network analyses of miRNA target genes and mRNA-seq data elucidated evidence for the functional involvement of miRNA dysregulation in the disease model. Utilization of the model for translational research identified several genes that were dysregulated in the patients with schizophrenia; hence, these genes may serve as biomarkers for schizophrenia. Therefore, future investigations into the data sets are warranted to translate the findings into benefits for patients with schizophrenia.

Funding

This work was supported by the National Natural Science Foundation of China (81703492), Beijing Natural Science Foundation (7182092), the Minzu University Research Fund (2018CXTD03), High-Level Hospital Development Program for Foshan “Climbing” Project, and the Minzu University of China 111 project.

Conflict of Interest

The authors have declared that there are no conflicts of interest in relation to the subject of this study.

Contributions of Authors

Y.C. conceived the study; Y.D. and Y.C. designed the research; and Y.D., X.S.L., L.C., and G.Y.C. conducted the research. All the authors analyzed and interpreted the data. Y.C. drafted the manuscript with critical revisions from all authors.

Supplementary Material

sbz114_suppl_Supplementary_Information
Click here for additional data file. (10.1MB, pdf)

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