Aberrant expression of miR-218 and miR-204 in human mesial temporal lobe epilepsy and hippocampal sclerosis-convergence on axonal guidance

Differential expression of miR-184 in temporal lobe epilepsy patients with and without hippocampal sclerosis - Influence on microglial function

Epilepsy is one of the most common neurological disorders characterized by recurrent seizures due to neuronal hyperexcitability. Here we compared miRNA expression patterns in mesial temporal lobe epilepsy with and without hippocampal sclerosis (mTLE + HS and mTLE −HS) to investigate the regulatory mechanisms differentiating both patient groups. Whole genome miRNA sequencing in surgically resected hippocampi did not reveal obvious differences in expression profiles between the two groups of patients. However, one microRNA (miR-184) was significantly dysregulated, which was confirmed by qPCR. We observed that overexpression of miR-184 inhibited cytokine release after LPS stimulation in primary microglial cells, while it did not affect the viability of murine primary neurons and primary astrocytes. Pathway analysis revealed that miR-184 is potentially involved in the regulation of inflammatory signal transduction and apoptosis. Dysregulation of some the potential miR-184 target genes was confirmed by qPCR and 3′UTR luciferase reporter assay. The reduced expression of miR-184 observed in patients with mTLE + HS together with its anti-inflammatory effects indicate that miR-184 might be involved in the modulation of inflammatory processes associated with hippocampal sclerosis which warrants further studies elucidating the role of miR-184 in the pathophysiology of mTLE.

Expression of microRNA-129-2-3p and microRNA-935 in plasma and brain tissue of human refractory epilepsy

OBJECTIVE

Numerous microRNAs (miRNAs) are differentially expressed in specific diseases, suggesting possible use as diagnostic or prognostic biomarkers. The purpose of this study is to investigate the expression levels of miR-129-2-3p and miR-935 in cortical brain tissue and plasma samples from controls and refractory temporal lobe epilepsy (TLE) patients to evaluate the utility of these measures as diagnostic biomarkers.

METHODS

The study was divided into three phases. First, cortical brain tissue samples from nine refractory TLE patients and eight controls were screened for differential miRNA expression using the Affymetrix miRNA 4.0 microarray. Second, real-time quantitative PCR (qRT-PCR) was used to verify the microarray results in brain tissue samples from 13 refractory TLE patients and 13 healthy controls (including those studied by microarray analysis). Third, we tested the expression levels of selected miRNAs in plasma samples from 25 refractory TLE patients and 25 healthy volunteers by qRT-PCR. The capacity of miR-129-2-3p and miR-935 expression to distinguish refractory TLE from health controls was tested by receiver operator characteristics (ROC) curve analysis.

RESULTS

(1) High-resolution miRNA arrays indicated that miR-129-2-3p and miR-935 were significantly upregulated in the cortical brain tissues of TLE patients compared to controls. (2) qRT-PCR confirmed upregulated miR-129-2-3p expression in the brain tissue(P<0.0001) and plasma samples(P=0.0008) of refractory TLE patients. (3) The expression of miR-935 in epilepsy patients was higher than control group, however, there are no significant statistical differences between them whether in plasma samples(P=0.644) or in tissue samples(P=0.258). (4) ROC analysis of miRNA-129-2-3p showed that the area under the curve (AUC) was 0.929 (95% CI: 0.833-1.000; p=0.000) for brain tissue and 0.778 (95% CI: 0.640-0.915; p=0.001) for plasma.

CONCLUSION

Expression of miRNA-129-2-3p was upregulated in cortical brain tissue and plasma samples from patients with refractory TLE, but miR-935 not. Plasma miRNA-129-2-3p has great potential as a non-invasive biomarker for early detection and clinical evaluation of refractory TLE.

Altered hippocampal microRNA expression profiles in neonatal rats caused by sevoflurane anesthesia: MicroRNA profiling and bioinformatics target analysis

Although accumulating evidence has suggested that microRNAs (miRNAs) have a serious impact on cognitive function and are associated with the etiology of several neuropsychiatric disorders, their expression in sevoflurane-induced neurotoxicity in the developing brain has not been characterized. In the present study, the miRNAs expression pattern in neonatal hippocampus samples (24 h after sevoflurane exposure) was investigated and 9 miRNAs were selected, which were associated with brain development and cognition in order to perform a bioinformatic analysis. Previous microfluidic chip assay had detected 29 upregulated and 24 downregulated miRNAs in the neonatal rat hippocampus, of which 7 selected deregulated miRNAs were identified by the quantitative polymerase chain reaction. A total of 85 targets of selected deregulated miRNAs were analyzed using bioinformatics and the main enriched metabolic pathways, mitogen-activated protein kinase and Wnt pathways may have been involved in molecular mechanisms with regard to neuronal cell body, dendrite and synapse. The observations of the present study provided a novel understanding regarding the regulatory mechanism of miRNAs underlying sevoflurane-induced neurotoxicity, therefore benefitting the improvement of the prevention and treatment strategies of volatile anesthetics related neurotoxicity.

Involvement of microRNAs in epileptogenesis

Patients who have sustained brain injury or had developmental brain lesions present a non-negligible risk for developing delayed epilepsy. Finding therapeutic strategies to prevent development of epilepsy in at-risk patients represents a crucial medical challenge. Noncoding microRNA molecules (miRNAs) are promising candidates in this area. Indeed, deregulation of diverse brain-specific miRNAs has been observed in animal models of epilepsy as well as in patients with epilepsy, mostly in temporal lobe epilepsy (TLE). Herein we review deregulated miRNAs reported in epilepsy with potential roles in key molecular and cellular processes underlying epileptogenesis, namely neuroinflammation, cell proliferation and differentiation, migration, apoptosis, and synaptic remodeling. We provide an up-to-date listing of miRNAs altered in epileptogenesis and assess recent functional studies that have interrogated their role in epilepsy. Last, we discuss potential applications of these findings for the future development of disease-modifying therapeutic strategies for antiepileptogenesis.

Genome-wide association study of periweaning failure-to-thrive syndrome (PFTS) in pigs

Porcine periweaning-failure-to-thrive syndrome (PFTS) is a condition that affects newly weaned piglets. It is characterised by a progressive debilitation leading to death, in the absence of infectious, nutritional, management or environmental factors. In this study, we present the first report of PFTS in South America and the results of a genome-wide association study to identify the genetic markers associated with the appearance of this condition in a crossbred swine population. Four chromosomal regions were associated with PFTS predisposition, one located on SSCX, one on SSC8, and the two other regions on SSC14. Regions on SSC8 and SSC14 harbour important functional candidate genes involved in human depression and might have an important role in PFTS. Our findings contribute to the increasing knowledge about this syndrome, which has been investigated since 2007, and to the identification of the aetiology of this disease.

Association of the genetic polymorphisms in pre-microRNAs with risk of childhood epilepsy in a Chinese population

PURPOSE

MicroRNA (miRNA), functions as gene regulators, plays crucial roles in pathogenesis of epilepsy. We hypothesized that single nucleotide polymorphisms (SNPs) in miRNA may be associated with childhood epilepsy.

METHOD

We first genotyped the selected four SNPs (miR-146a rs57095329, miR-149 rs2292832, miR-196a2 rs11614913, and miR-499 rs3746444) in 267 paired childhood epilepsy patients and controls using the TaqMan assay, and evaluated the associations of the four SNPs with the risk of epilepsy. In addition, we evaluated the associations of these SNPs with drug-resistance in 95 drug-resistant and 172 drug-responsive epilepsy patients. Furthermore, the genotype-phenotype correlation was assessed in 95 drug-resistant epilepsy patients.

RESULTS

The selected four SNPs (miR-146a rs57095329, miR-149 rs2292832, miR-196a2 rs11614913, and miR-499 rs3746444) were not significantly different between epilepsy patients and controls (P>0.05 for all). However, the miR-146a rs57095329 A/G genotypes were significantly associated with increased drug-resistance risk of epilepsy patients in allelic comparison (OR=2.363, 95%CI=1.608-3.472, P<0.001), heterozygote model (OR=2.341, 95%CI=1.301-4.211, P=0.005), homozygote model (OR=1.791, 95%CI=1.239-2.589, P=0.002), dominant model (OR=2.625, 95%CI=1.558-4.425, P<0.001), and recessive model (OR=2.336, 95%CI=1.166-4.673, P=0.017). Moreover, subjects with the rs57095329 GG genotype had significantly higher NHS3 score than subjects with AA genotype (P<0.001) and AG genotype (P=0.013) in the drug resistant patients.

CONCLUSION

miR-146a rs57095329 polymorphism might be involved in the genetic susceptibility to drug-resistance and seizure severity in childhood epilepsy patients.

Differential gene expression in dentate granule cells in mesial temporal lobe epilepsy with and without hippocampal sclerosis

OBJECTIVE

Hippocampal sclerosis is the most common neuropathologic finding in cases of medically intractable mesial temporal lobe epilepsy. In this study, we analyzed the gene expression profiles of dentate granule cells of patients with mesial temporal lobe epilepsy with and without hippocampal sclerosis to show that next-generation sequencing methods can produce interpretable genomic data from RNA collected from small homogenous cell populations, and to shed light on the transcriptional changes associated with hippocampal sclerosis.

METHODS

RNA was extracted, and complementary DNA (cDNA) was prepared and amplified from dentate granule cells that had been harvested by laser capture microdissection from surgically resected hippocampi from patients with mesial temporal lobe epilepsy with and without hippocampal sclerosis. Sequencing libraries were sequenced, and the resulting sequencing reads were aligned to the reference genome. Differential expression analysis was used to ascertain expression differences between patients with and without hippocampal sclerosis.

RESULTS

Greater than 90% of the RNA-Seq reads aligned to the reference. There was high concordance between transcriptional profiles obtained for duplicate samples. Principal component analysis revealed that the presence or absence of hippocampal sclerosis was the main determinant of the variance within the data. Among the genes up-regulated in the hippocampal sclerosis samples, there was significant enrichment for genes involved in oxidative phosphorylation.

SIGNIFICANCE

By analyzing the gene expression profiles of dentate granule cells from surgically resected hippocampal specimens from patients with mesial temporal lobe epilepsy with and without hippocampal sclerosis, we have demonstrated the utility of next-generation sequencing methods for producing biologically relevant results from small populations of homogeneous cells, and have provided insight on the transcriptional changes associated with this pathology.

miRNAs: biological and clinical determinants in epilepsy

Recently, microRNAs (miRNAs) are reported to be crucial modulators in the pathogenesis and potential treatment of epilepsies. To date, several miRNAs have been demonstrated to be significantly expressed in the epileptic tissues and strongly associated with the development of epilepsy. Specifically, miRNAs regulate synaptic strength, inflammation, neuronal and glial function, ion channels, and apoptosis. Furthermore, peripheral blood miRNAs can also be utilized as diagnostic biomarkers to assess disease risk and treatment responses. Here, we will summarize the recent available literature regarding the role of miRNAs in the pathogenesis and treatment of epilepsy. Moreover, we will provide brief insight into the potential of miRNA as diagnostic biomarkers for early diagnosis and prognosis of epilepsy.

microRNA and Epilepsy

Epilepsy is a common, serious neurological disease characterized by recurring seizures. Such abnormal, excessive synchronous firing of neurons arises in part because of imbalances in excitation and inhibition in the brain. The process of epileptogenesis, during which the normal brain is transformed after injury to one capable of generating spontaneous seizures, is associated with large-scale changes in gene expression. These contribute to the remodelling of brain networks that permanently alters excitability. Components of the microRNA (miRNA) biogenesis pathway have been found to be altered in brain tissue from epilepsy patients and experimental epileptogenic insults result in select changes to miRNAs regulating neuronal microstructure, cell death, inflammation, and ion channels. Targeting key miRNAs has been shown to alter brain excitability and suppress or exacerbate seizures, indicating potential for miRNA-based therapeutics in epilepsy. Altered miRNA profiles in biofluids may be potentially useful biomarkers of epileptogenesis. In summary, miRNAs represent an important layer of gene expression control in epilepsy with therapeutic and biomarker potential.