Effect of methanol fixation on single cell RNA sequencing of the murine dentate gyrus (droplet-based scRNAseq).
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ABSTRACT: We evaluated the effect of methanol (MeOH) fixation on adult murine dentate gyrus (DG) single cell suspensions processed with droplet-based scRNA-seq.
Project description:Single-cell transcriptomics methods have become very popular to study the cellular composition of organs and tissues and characterize the expression profiles of the individual cells that compose them. The main critical step for single-cell transcriptomics methods is sample preparation. Several methods have been developed to preserve cells after sample dissociation to uncouple sample handling from library preparation. Yet, the suitability of these methods depends on the types of cells to be processed. In this project, we perform a systematic comparison of preservation methods for droplet-based single-cell RNA-seq (scRNA-seq) on human neural progenitor cell populations derived from induced pluripotent stem cells (iPSCs) and highlight their strengths and weaknesses. We compared the cellular composition and expression profile of single-cell suspensions from fresh NPCs with that of NPCs preserved with Dimethyl Sulfoxide (DMSO), Methanol, vivoPHIX and Acetil-methanol (ACME). Our results show that while DMSO provides the highest cell quality in terms of RNA molecules and genes detected per cell. Yet, it strongly affects the cellular composition and the expression profile of the resulting datasets. In contrast, methanol fixed samples display a cellular composition like that of fresh samples while providing a good cell quality and smaller expression biases. Taken together, our results show that methanol fixation is the method of choice for performing droplet-based single-cell transcriptomics experiments on neural cell populations.
Project description:We investigated the transcriptome of dentate gyrus (DG) granule cells in postmortem hippocampus from 79 subjects with mental illness (schizophrenia, bipolar disorder, major depression) or non-psychiatric controls.
Project description:Neuronal activity-dependent gene expression plays important roles in neural plasticity. We use electroconvulsive stimulation (ECS) as an in vivo model for neuronal activation to identify genes that are regulated by neuronal activity. Dentate gyri (DG) were microdissected 4 hours after sham or ECS treatment for gene expression profiling. 4 total samples were analysed (2 for each condition). Averaged expression values between sham and ECS samples were pair-wise compared.
Project description:Neuronal activity-dependent gene expression plays important roles in neural plasticity. We use electroconvulsive stimulation (ECS) as an in vivo model for neuronal activation to identify genes that are regulated by neuronal activity. Dentate gyri (DG) were microdissected 4 hours after sham or ECS treatment for gene expression profiling.
Project description:Temporal lobe epilepsy (TLE) is the most frequent type of focal epilepsy in adults, typically resistant to pharmacological treatment and mostly present with cognitive impairment and psychiatric comorbidities. The most common neuropathological hallmark in TLE patients is hippocampal sclerosis(HS). However, the underlying molecular mechanisms involved remain poorly characterized. Dentate gyrus(DG), one specific hippocampal subarea, structural and functional changes imply a key involvement of the DG in the development of TLE. In this study, isobaric tags for relative and absolute quantitation (iTRAQ) -based quantitative proteomic technique was performed to analysis of hippocampal DG obtained from patients with TLE-HS compared to control samples obtained from the autopsy. Our proteomic data identified 5583 proteins, of which 82 proteins were up-regulated and 90 proteins were down-regulated. Bioinformatics analysis indicated that differential expressed proteins enriched in “synaptic vesicle”, “mitochondrion”, “cell-cell adhesion”, “regulation of synaptic plasticity”, “ATP binding” and “Oxidative phosphorylation”. Protein-protein interaction network analysis found a pivotal module of 10 proteins that relate to “Oxidative phosphorylation”. This study is the first to investigate proteomic alterations in DG region of TLE-HS patients, and pave the way to better understanding of epileptogenesis mechanisms and future therapeutic intervention.
Project description:During senescence of detached rice leaves, tryptophan (Trp) and Trp-derived secondary metabolites such as serotonin and 4-coumaroylserotonin accumulated in concert with methanol (MeOH) production. This senescence-induced MeOH induction was closely associated with levels of pectin methylesterase (PME)1 mRNA and PME enzyme activity. Exogenous challenge of detached rice leaves with 1% MeOH accelerated Trp and serotonin biosynthesis with induction of the corresponding genes. No other solvents including ethanol resulted in a Trp-inducing effect. This MeOH-induced Trp synthesis was positively regulated by abscisic acid but negatively regulated by cytokinin, suggesting hormonal involvement on the action of MeOH. Endogenous overproduction or suppression of MeOH either by PME1 overexpression or RNAi gene silencing revealed that PME1 overexpressing lines produced twofold higher Trp levels with elevated Trp biosynthetic gene expression, whereas RNAi lines showed twofold reduction in Trp level in healthy control rice leaves, suggesting that MeOH acts as an endogenous elicitor to enhance Trp biosynthesis. Among many transcription factors induced following MeOH treatment, the WRKY family showed significant induction patterns of which WRKY14 appeared to play a key regulatory role in MeOH-induced Trp and Trp-derived secondary metabolite biosynthesis.