Project description:Background: Major Depressive Disorder (MDD) represents a major social and economic health issue and constitutes a major risk factor for MDD suicide. The molecular pathology of suicidal depression remains poorly understood, although it has been hypothesized that regulatory genomic processes are involved in the pathology of both MDD and suicidality. Methods: Genome-wide patterns of DNA methylation were assessed in depressed MDD suicide completers (n=20) and compared to non-psychiatric, sudden-death controls (n=20) using tissue from two cortical brain regions (Brodmann Area 11 (BA11) and Brodmann Area 25 (BA25)). Analyses focussed on identifying differentially methylated regions (DMRs) associated with suicidal depression, and epigenetic variation was explored in the context of polygenic risk scores for major depression and MDD suicide. Weighted gene co-methylation network analysis was used to identify modules of co-methylated loci associated with depressed MDD suicide completers and polygenic burden for MDD and MDD suicide attempt. Results: We identified a DMR upstream of the PSORS1C3 gene, subsequently validated using bisulfite-pyrosequencing and replicated in a second set of MDD suicide samples, which is characterized by significant hypomethylation in both cortical brain regions in MDD MDD suicide cases. We also identified discrete modules of co-methylated loci associated with polygenic risk burden for MDD suicide attempt, but not major depression. MDD suicide-associated co-methylation modules were enriched among gene networks implicating biological processes relevant to depression and suicidality, including nervous system development and mitochondria function. Conclusions: Our data suggest there are coordinated changes in DNA methylation associated with MDD suicide that may offer novel insights into the molecular pathology associated with depressed MDD suicide completers.
Project description:Brain gene expression profiling studies of suicide and depression using oligonucleotide microarrays have often failed to distinguish these two phenotypes. Moreover, next generation sequencing approaches are more accurate in quantifying gene expression and can detect alternative splicing. Using RNA-seq, we examined whole-exome gene and exon expression in non-psychiatric controls (CON, N=29), DSM-IV major depressive disorder suicides (MDD-S, N=21) and MDD non-suicides (MDD, N=9) in the dorsal lateral prefrontal cortex (Brodmann Area 9) of sudden death medication-free individuals post mortem. Using small RNA-seq, we also examined miRNA expression (nine samples per group). DeSeq2 identified 35 genes differentially expressed between groups and surviving adjustment for false discovery rate (adjusted P<0.1). In depression, altered genes include humanin-like-8 (MTRNRL8), interleukin-8 (IL8), and serpin peptidase inhibitor, clade H (SERPINH1) and chemokine ligand 4 (CCL4), while exploratory gene ontology (GO) analyses revealed lower expression of immune-related pathways such as chemokine receptor activity, chemotaxis and cytokine biosynthesis, and angiogenesis and vascular development in (adjusted P<0.1). Hypothesis-driven GO analysis suggests lower expression of genes involved in oligodendrocyte differentiation, regulation of glutamatergic neurotransmission, and oxytocin receptor expression in both suicide and depression, and provisional evidence for altered DNA-dependent ATPase expression in suicide only. DEXSEq analysis identified differential exon usage in ATPase, class II, type 9B (adjusted P<0.1) in depression. Differences in miRNA expression or structural gene variants were not detected. Results lend further support for models in which deficits in microglial, endothelial (blood-brain barrier), ATPase activity and astrocytic cell functions contribute to MDD and suicide, and identify putative pathways and mechanisms for further study in these disorder
Project description:The serotonergic system and in particular serotonin 1A receptor (5-HT1AR) are critically implicated in major depressive disorder (MDD), although underlying mechanisms remain enigmatic. Here we demonstrated that 5-HT1AR is palmitoylated in human and rodent brains and identified ZDHHC21 as a major palmitoyl-transferase, whose depletion reduced palmitoylation and consequently signaling functions of 5-HT1AR. Two rodent models for depression show reduced brain ZDHHC21 expression in conjunction with attenuated 5-HT1AR palmitoylation. Moreover, selective knock-down of ZDHHC21 in murine forebrain by itself sufficed to provoke depressive symptoms, demonstrating a causal relationship between 5-HT1AR palmitoylation and depression. Regarding the underlying mechanism, we identified the microRNA miR-30e as a negative regulator of Zdhhc21 expression. By analysis of the post-mortem samples from suicide MDD victims we also found ZDHHC21 expression as well as palmitoylation of 5-HT1AR to be specifically reduced within the prefrontal cortex (PFC), a brain area critically involved in the pathogenesis of depressive symptoms. Our study provides evidence for transcriptional downregulation of 5-HT1AR palmitoylation as a central mechanism in the etiology of depression and even suicide, in effect making the restoration of 5-HT1AR palmitoylation a promising clinical strategy for the treatment of major depressive disorder.
Project description:RNAs were extracted from entorhinal cortex of human suicide patients with major depression and matched control subjects. The transcription profile was investigated by Agilent microarray platform and quantitative real-time PCR to reveal alterations in neuronal functions in this brain region.
Project description:32 genes of a previously established inflammation-related gene signature were assessed in 197 patients with MDD and 151 controls collected during the EU-MOODINFLAME project. Monocyte gene expression data were related to age, gender, BMI, depression severity, Childhood Adversity (CA), and Suicide Risk (SR) data studycenter 2
Project description:32 genes of a previously established inflammation-related gene signature were assessed in 197 patients with MDD and 151 controls collected during the EU-MOODINFLAME project. Monocyte gene expression data were related to age, gender, BMI, depression severity, Childhood Adversity (CA), and Suicide Risk (SR) data studycenter 1
Project description:32 genes of a previously established inflammation-related gene signature were assessed in 197 patients with MDD and 151 controls collected during the EU-MOODINFLAME project. Monocyte gene expression data were related to age, gender, BMI, depression severity, Childhood Adversity (CA), and Suicide Risk (SR) data studycenter 3
Project description:Major depressive disorder (MDD) is a complex and potentially debilitating illness whose etiology and pathology remains unclear. Non-coding RNAs have been implicated in MDD, where they display differential expression in the brain and the periphery. In this study, we quantified small nucleolar RNA (snoRNA) expression by small RNA sequencing in the lateral habenula (LHb) of individuals with MDD (n=15) and psychiatrically-healthy controls (n=15). We uncovered five snoRNAs that exhibited differential expression between MDD and controls (FDR<0.01). Specifically, SNORA69 showed increased expression in MDD and was technically validated via RT-qPCR. We further investigated the expression of Snora69 in the LHb and peripheral blood of an unpredicted chronic mild stress (UCMS) mouse model of depression. Snora69 was specifically up-regulated in mice that underwent the UCMS paradigm. SNORA69 is known to guide pseudouridylation onto 5.8S and 18S rRNAs. We quantified the relative abundance of pseudouridines on 5.8S and 18S rRNA in human post-mortem LHb samples and found increased abundance of pseudouridines in the MDD group. Overall, our findings indicate the importance of brain snoRNAs in the pathology of MDD, and the first study to investigate snoRNA expression in MDD. Future studies characterizing SNORA69’s role in MDD pathology is warranted.