MicroRNA Expression Is Down-Regulated and Reorganized in Prefrontal Cortex of Depressed Suicide Subjects

<div><h3>Background</h3><p>Recent studies suggest that alterations in expression of genes, including those which regulate neural and structural plasticity, may be crucial in the pathogenesis of depression. MicroRNAs (miRNAs) are newly discovered regulators of gene expression that have recently been implicated in a variety of human diseases, including neuropsychiatric diseases.</p> <h3>Methodology/Principal Findings</h3><p>The present study was undertaken to examine whether the miRNA network is altered in the brain of depressed suicide subjects. Expression of miRNAs was measured in prefrontal cortex (Brodmann Area 9) of antidepressant-free depressed suicide (n = 18) and well-matched non-psychiatric control subjects (n = 17) using multiplex RT-PCR plates. We found that overall miRNA expression was significantly and globally down-regulated in prefrontal cortex of depressed suicide subjects. Using individual tests of statistical significance, 21 miRNAs were significantly decreased at p = 0.05 or better. Many of the down-regulated miRNAs were encoded at nearby chromosomal loci, shared motifs within the 5′-seeds, and shared putative mRNA targets, several of which have been implicated in depression. In addition, a set of 29 miRNAs, whose expression was not pairwise correlated in the normal controls, showed a high degree of co-regulation across individuals in the depressed suicide group.</p> <h3>Conclusions/Significance</h3><p>The findings show widespread changes in miRNA expression that are likely to participate in pathogenesis of major depression and/or suicide. Further studies are needed to identify whether the miRNA changes lead to altered expression of prefrontal cortex mRNAs, either directly (by acting as miRNA targets) or indirectly (e.g., by affecting transcription factors).</p> </div

Gene Expression and Epigenetic Modifications in Stress Response Genes Associated with Teenage and Adult

Suicide is a preventable public health issue that accounts for over a million deaths worldwide and is associated with the interaction of several biological, environmental, and neurological factors. Repeatedly, a dysregulated hypothalamic-pituitary-adrenal (HPA) axis has been demonstrated to play a fundamental role and associated with psychiatric disorders and suicide, yet the mechanisms underlying this dysregulation are not clear. Decreased expression of the glucocorticoid receptor (GR) which is highly expressed in the hippocampus and prefrontal cortex (PFC) and is susceptible to epigenetic modulation is a strong indicator of HPA-axis hyperactivity. Additionally, epigenetic mechanisms have been shown to mediate environment x gene interaction through susceptible genes resulting in long-term changes to the genome. One of the most studied epigenetic mark, DNA methylation (DNAm) has been demonstrated to play a major role in various diseases including suicide. The main goal of this thesis was to test the hypothesis that HPA-axis coupled genes are dysregulated in specific areas of the limbic system and that epigenetic reprogramming, in the form of DNAm, maybe a key underlying factor mediating impaired GR signaling. Since there are distinct neurodevelopmental changes occurring during adolescence that may change the endophenotypes of suicide, teenage suicide-completers were studied separately from adult suicide-completers. In teenage suicide-completers, a focused approach was used to identify HPA-axis coupled genes that are differentially expressed and determine significant methylation changes at specific loci of candidate genes. To investigate steady-state DNAm levels, we analyzed DNA methyltransferases (DNMTs), ten-eleven translocation enzymes (TETs), and growth arrest- and DNA-damage-inducible proteins (GADD45) in both PFC and hippocampus. In adult suicide-completers, a hypothesis-free, genome-wide approach was taken to determine DNAm changes specific to neurons in the PFC. Initial bioinformatics reveals novel molecular pathways and networks where epigenetic regulation may be playing a key underlying factor. Together, these findings enhance our understanding of the complex transcriptional regulation of GR gene and also identify key regulators involved in HPA-axis dysregulation. Integrating DNAm and gene expression analysis provides valuable insight into molecular changes and help develop our current knowledge of how epigenetics contributes to alterations in molecular pathways involved in the pathophysiology of suicide

Expression of p21-activated kinases 1 and 3 is altered in the brain of subjects with depression

The p21-activated kinases (PAKs) of group I are the main effectors for the small Rho GTPases, critically involved in neurodevelopment, plasticity and maturation of the nervous system. Moreover, the neuronal complexity controlled by PAK1/PAK3 signaling determines the postnatal brain size and synaptic properties. Stress induces alterations at the level of structural and functional synaptic plasticity accompanied by reductions in size and activity of the hippocampus and the prefrontal cortex (PFC). These abnormalities are likely to contribute to the pathology of depression and, in part, reflect impaired cytoskeleton remodeling pointing to the role of Rho GTPase signaling. Thus, the present study assessed the expression of the group I PAKs and their activators in the brain of depressed subjects. Using quantitative polymerase chain reaction (qPCR), mRNA levels and coexpression of the group I PAKs: PAK1, PAK2, and PAK3 as well as of their activators: RAC1, CDC42 and ARHGEF7 were examined in postmortem samples from the PFC (n = 25) and the hippocampus (n = 23) of subjects with depression and compared to control subjects (PFC n = 24; hippocampus n = 21). Results demonstrated that mRNA levels of PAK1 and PAK3, are significantly reduced in the brain of depressed subjects, with PAK1 being reduced in the PFC and PAK3 in the hippocampus. No differences were observed for the ubiquitously expressed PAK2. Following analysis of gene coexpression demonstrated disruption of coordinated gene expression in the brain of subjects with depression. Abnormalities in mRNA expression of PAK1 and PAK3 as well as their altered coexpression patterns were detected in the brain of subjects with depression.Fil: Fuchsova, Beata. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas ; ArgentinaFil: Alvarez Juliá, Anabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas ; ArgentinaFil: Rizavi, Hooriyah S.. University of Illinois; Estados UnidosFil: Frasch, Alberto Carlos C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas ; ArgentinaFil: Pandey, Ghanshyam N.. University of Illinois; Estados Unido

Altered Wnt signalling in the teenage suicide brain: focus on glycogen synthase kinase-3b and b-catenin

Glycogen synthase kinase (GSK)-3β and β-catenin are important components of the Wnt signalling pathway, which is involved in numerous physiological functions such as cognition, brain development and cell survival. Their abnormalities have been implicated in mood disorders and schizophrenia. Teenage suicide is a major public health concern; however, very little is known about its neurobiology. In order to examine if abnormalities of GSK-3β and β-catenin are associated with teenage suicide, we determined the gene and protein expression of GSK-3β and β-catenin in the prefrontal cortex (PFC) and hippocampus obtained from 24 teenage suicide victims and 24 normal control subjects. Protein expression was determined using Western blot with specific antibodies and gene expression (mRNA levels) was determined using the real-time polymerase chain reaction method. No significant change was observed in the GSK-3β protein levels either in the PFC or hippocampus of suicide victims compared to controls. However, protein levels of pGSK-3β-ser9 were significantly decreased in the PFC and hippocampus of suicide victims compared to normal controls. We also found that GSK-3β mRNA levels were significantly decreased in the PFC but not in the hippocampus of teenage suicide victims compared to controls. Mean protein and mRNA levels of β-catenin were significantly decreased in both the PFC and hippocampus of teenage suicide group compared to controls. The observation that there is a decrease in β-catenin and pGSK-3β-ser9 in the PFC and hippocampus of teenage suicide victims does indicate a disturbance in the Wnt signalling pathway in teenage suicide

Characteristics of subjects in the depressed suicide and normal control groups.

<p>Characteristics of subjects in the depressed suicide and normal control groups.</p

Plot of Mean vs standard deviation (SD) for normal control and depressed suicide groups.

<p>miRNA expression in the depressed suicide group is significantly <i>less</i> variable than in the control group.</p

microRNAs down-regulated in depressed suicide as determined by individual tests of statistical significance.

<p>microRNAs down-regulated in depressed suicide as determined by individual tests of statistical significance.</p

Quantile rank analysis of miRNA expression data.

<p>Quantile rank analysis of miRNA expression data.</p

Protein levels of DNMT3b, BCL2, and VEGFA in PFC of depressed suicide (n = 18) and normal control (n = 17) subjects.

<p>Protein samples from tissue lysates were subjected to 10% polyacrylamide gel electrophoresis and transferred to enhanced chemiluminescence–nitrocellulose membranes, which were then incubated with primary antibody specific for DNMT3b, BCL2, VEGFA or β-actin and corresponding secondary antibody. The suicide group was compared with the control group. DMNT3b was strongly up-regulated (2.4-fold) in the depressed suicide group (^ap = 1×10⁻¹¹), VEGFA showed no significant change (1.03-fold, ^bp = 0.4) and BCL2 was strongly down-regulated (0.57 of control, ^cp = 2.4×10⁻¹⁴). C = Controls; DS = Depressed suicide.</p