| Background Depression is among the leading contributors to the global burden of disease,affecting approximately 17% of the population in the USA.It is associated with enormous personal suffering and societal economic burden.Furthermore,depression can be a lethal illness owing to an elevated risk for suicide,as well as increased risks of cardiac disease,cerebrovascular disorders and other medical causes of mortality.According to the survey of the China Center for Disease Control and Prevention,the incidence of depression in China is over 4%,and the number of patients is over 30 million,which has become one of the major diseases affecting the helth of people.It is generally believed that the occurrence of depression is the result of the combination of genetic,immuno-inflammatory and environmental factors,and its pathogenesis is still not fully elucidated.The mainstream view of depression pathogenesis is insufficient of norepinephrine,serotonin,dopamine,and other single amine neurotransmitter levels,so the clinical use of antidepressant drugs are mainly through improving the level of single amine neurotransmitter.However,there are clinical effect lag,not exact curative effect,side effects such as big shortcoming.In recent years,a large number of researchers worldwide have been working on new targets for depression.According to a study on patients and rodent models,epigenetic changes including modified histones and DNA,which is caused by the stress,are associated with depression.It also proves the potential significance of these epigenetic changes.Genetic abnormalities explain the susceptibility of 35 to 40 percent of depressed patients.Early genetic studies focused on candidate genes related the treatment such as genes encoding monoamine receptors and transporters.Recent genome-wide association studies have been successful in identifying gene locus in schizophrenia,but not in patients with major depressive disorder(MDD).This is due to the fact that the number of MDD cases in the existing study is small,and it is estimated that 7.5 to 100,000 cases will be required to produce statistically significant repeatable findings.The size of the sample size may be due to clinical heterogeneity,with a moderate genetic force(~ 40%)and the genetic complexity of depression,which is the locus of interaction and the magnitude of the effect.In spite of this,more than 60000 cases were analyzed in recent GWAS pathways.There is a significant correlation between the immune,neurons signal,the density of synapse,and histone level and mental illness including MDD.This suggests that there is a risk in these pathways variable clustering.As the number of clinical samples increases,the next generation sequencing may identify a rare single nucleotide variant or rare copy number mutation that causes the genetic risk of MDD.The interaction between genetic vulnerability and environmental susceptibility is most likely to lead to the complexity and heterogeneity of depression.These studies have focused on early life stress or trauma,but study the interaction between genes and environment is growing,including protective factors of social support and intervention,and enhances the capacity of antidepressant genes.Genes are regulated by micro RNAs(mi RNAs)activity,and mi RNAs can be used as fine tuners and switches for gene expression.Micro RNA about 22 nucleotides is a kind ofnon-coding single stranded RNA molecule encoded by endogenous gene,which is involved in the regulation of gene expression after transcription.In addition to the normal physiological processes,it is closely related to the pathogenesis of diabetes,cardiovascular disease,tumor,autoimmune diseases,mental illness,and so on.At the same time,the central nervous system function also plays a crucial regulatory role.Therefore,mi RNA is regarded as a key molecule of gene expression regulation and receives more and more attention.The literature indicates that the mi RNA expression level changes in the preclinical model of patients with depression and psychological stress.Patients with depression have high levels of neurologic dysfunction,a disorder associated with many mi RNA expression disorders.These results strongly suggest that mi RNA,as a gene regulator,is involved in the development and synaptic transmission of depression.Obviously,changes in mi RNA expression can affect the expression of many genes related to neural activity in the brain,so as to participate in the occurrence and development of depression.This topic will further clarify the role of mi RNA in antidepressant therapy and clarify the molecular mechanism of mi RNA function.Present study combinines the methods of electrophysiology,molecular biology and bioinformatics and ethology to explore potential therapeutic targets for antidepressant therapy,and expects to provide new ideas and theoretical basis for clinical treatment.Aims The model of depression was constructed,and successfully verified by behavioral test.Micro RNA molecules that are explicitly involved in depression were identified by gene chip alignment techniques.To explore the potential treatmentby targeting on micro RNA,we applied brain localization injection adeno-associated virus and pharmacological treatment in the model mice.Metholds1.Building of mouse model for depression: We used chronic mild and unpredictable stress stimulation to prepare the mouse model of depression,and detected depressive behavior in mice through behavioral and protein expression.Behavioral tests included forcedswimming,open field experiment,elevated plus maze cross,tail suspention test,etc.2.By using gene chip technology,we tested mi RNAs molecules that may be involved in depression.The samples were verified by real-time PCR method.3.Synthetic mimics and inhibitors of candidate mi RNAs were injedted by brain location technology to amygdala.Green fluorescent expression confirmed the injection site.The behaviors of mice were further verified by behavioral experiments.4.Go analysis was used to calculate the differences with the Go classification of a particular branch of hypergeometric distribution.According to the selected difference genes,we calculated the geometric distribution of these differentially expressed genes through pathway analysis.The target genes were selected to validate the relevant networks by Western blot.Results1.Model mice showed less time in the central activity of the open field test,and increased the immobilized time in forced swimming and tail suspention tests.Western blot found that amygdala and prefrontal cortex were hyperactive brain regions in the models..The above results show that the model of depression is successful.2.The microarray detection results showed that significantly up-regulated genes were mi R-150-5p,mi R-434-3p,mi R-467 f,mi R-30c-5p,mi R-708-5p,and mi R-3963.Significantly decreased genes were mi R-377-3p,mi R-10a-5p,mi R-204-3p,mi R-505-5p,mi R-28 b,mi R-100-5p,etc.These genes were further verified by real-time PCR.3.mi R-30c-5p and mi R-3963 were selected for the further study.The mimics and inhibitors of this two mi RNAs were injected into amygdala.The activity of central time,Injection of mi R-30c-5p and mi R-3963 inhibitors reversed the behaviors in forced swimming and tail suspension test.However,injection of micics for mi R-30c-5p and mi R-3963 had no effects on the depressionlike behavioiors.4.Go analysis results analysised the micro RNA molecules that are selected for differential expression.To clear the corresponding target genes including GRM3,GRM5,Calcr,Real-time PCR method was used to verify the corresponding m RNA level changes.Resultsshowed the mi RNAs combined with targeted m RNAs and inhibited translation,but did not destroy and affect the stability.Western blot verified the above changes in protein expression.Conclusions The model of CUMS was successfully tested by the behavior and western blot.By bioinformatics method,mi RNA with abnormal expression in depression model mice was verified by RT-PCR.Behavioral experiments confirmed that local injection of mi RNA inhibitor in the amygdala alleviated the depressive symptoms.These results suggest that mi RNA,as a gene regulator,is involved in the development and synaptic transmission of depression.This study provides a new target for the research and development of anti-depressant drugs,and provides a theoretical basis for the development of anti-depression drugs based on micro RNA. |
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