ABSTRACT: Unbiased 'omics' techniques, such as next generation RNA-sequencing, can provide entirely novel insights into biological systems. However, cellular heterogeneity presents a significant barrier to analysis and interpretation of these datasets. The neurons of the dorsal root ganglia (DRG) are an important model for studies of neuronal injury, regeneration and pain. The majority of investigators utilize a dissociated preparation of whole ganglia when studying cellular and molecular function. We demonstrate that the standard methods for producing these preparations gives a 10%-neuronal mixture of cells, with the remainder of cells constituting satellite glia and other non-neuronal cell types. Using a novel application of magnetic purification, we consistently obtain over 95% pure, viable neurons from adult tissue, significantly enriched for small diameter nociceptors expressing the voltage gated ion channel Nav1.8. Using genome-wide RNA-sequencing we compare the currently used (10% neuronal) and pure (95% nociceptor) preparations and find 920 genes enriched. This gives an unprecedented insight into the molecular composition of small nociceptive neurons in the DRG, potentially altering the interpretation of previous studies performed at the tissue level, and indicating a number of novel markers of this widely-studied population of cells. We anticipate that the ease of use, affordability and speed of this technique will see it become widely adopted, delivering a greatly improved capacity to study the roles of nociceptors in health and disease. RNA-Seq was performed for 4 biological replicates from three different groups: intact DRG, acutely dissociated DRG and magnetically-purified DRG neurons. Differential expression was analyzed between acutely dissociated and MACS-dissociated samples to define the 'nociceptor transcriptome'.
Project description:Unbiased 'omics' techniques, such as next generation RNA-sequencing, can provide entirely novel insights into biological systems. However, cellular heterogeneity presents a significant barrier to analysis and interpretation of these datasets. The neurons of the dorsal root ganglia (DRG) are an important model for studies of neuronal injury, regeneration and pain. The majority of investigators utilize a dissociated preparation of whole ganglia when studying cellular and molecular function. We demonstrate that the standard methods for producing these preparations gives a 10%-neuronal mixture of cells, with the remainder of cells constituting satellite glia and other non-neuronal cell types. Using a novel application of magnetic purification, we consistently obtain over 95% pure, viable neurons from adult tissue, significantly enriched for small diameter nociceptors expressing the voltage gated ion channel Nav1.8. Using genome-wide RNA-sequencing we compare the currently used (10% neuronal) and pure (95% nociceptor) preparations and find 920 genes enriched. This gives an unprecedented insight into the molecular composition of small nociceptive neurons in the DRG, potentially altering the interpretation of previous studies performed at the tissue level, and indicating a number of novel markers of this widely-studied population of cells. We anticipate that the ease of use, affordability and speed of this technique will see it become widely adopted, delivering a greatly improved capacity to study the roles of nociceptors in health and disease.
Project description:The goal of this study was to analyze global gene expression in specific populations of nociceptor sensory neurons, the neurons that detect damaging/noxious stimuli. The dorsal root ganglia (DRG), trigeminal ganglia, and nodose ganglia are anatomically distinct peripheral sensory ganglia that contain nociceptors which innervate skin, gut, lungs, and other distinct organ tissues. We used flow cytometry to purify nociceptors from these ganglia and profiled their global gene expression signatures to compare gene expression between these different anatomically distinct nociceptors. Nav1.8-Cre were bred with Rosa26-TdTomato to generate Nav1.8-Cre/R26-TdTomato reporter progeny, where all peripheral nociceptor neurons are genetically marked with red fluroescence due to specific expression of the TTX- resistant sodium channel Nav1.8. Lumbar region dorsal root ganglia (DRG), trigeminal ganglia, and nodose ganglia were dissected from mice (3 mice were pooled/sample). Highly red fluorescent neurons were Facs purified, RNA extracted, and processed for microarray analysis.
Project description:Nociceptors play an essential role in both acute pain and chronic pain conditions. In this study, we examined the proteome of mouse dorsal root ganglia and compared NaV1.8Cre+/-; ROSA26-flox-stop-flox-DTA (Diphtheria toxin fragment A) mutant mice (NaV1.8Cre-DTA), in which NaV1.8-positive neurons (mainly nociceptors) in dorsal root ganglia (DRG) were ablated, with respective littermate wildtype controls.
Project description:The goal of this study was to analyze global gene expression in specific populations of nociceptor sensory neurons, the neurons that detect damaging/noxious stimuli. The dorsal root ganglia (DRG), trigeminal ganglia, and nodose ganglia are anatomically distinct peripheral sensory ganglia that contain nociceptors which innervate skin, gut, lungs, and other distinct organ tissues. We used flow cytometry to purify nociceptors from these ganglia and profiled their global gene expression signatures to compare gene expression between these different anatomically distinct nociceptors.
Project description:During embryogenesis, nociceptive sensory neurons of the dorsal root ganglia depend intimately on Nerve Growth Factor (NGF) for neuronal survival, maturation and target innervation. NGF is a secreted molecular signal synthesized by neuronal target tissues. In developing nociceptors, NGF engages the receptor tyrosine kinase TrkA to activate a gene transcriptional program involving the regulation of hundreds of transcripts. To identify NGF-dependent genes in developing mouse nociceptors, we have designed and performed two separate microarray screens to compare gene expression profiles of DRG neurons either with or lacking NGF signaling.
Project description:During embryogenesis, nociceptive sensory neurons of the dorsal root ganglia depend intimately on Nerve Growth Factor (NGF) for neuronal survival, maturation and target innervation. NGF is a secreted molecular signal synthesized by neuronal target tissues. In developing nociceptors, NGF engages the receptor tyrosine kinase TrkA to activate a gene transcriptional program involving the regulation of hundreds of transcripts. To identify NGF-dependent genes in developing mouse nociceptors, we have designed and performed two separate microarray screens to compare gene expression profiles of DRG neurons either with or lacking NGF signaling. For the first screen comparing DRGs of BaxM-bM-^HM-^R/M-bM-^HM-^R and NgfM-bM-^HM-^R/M-bM-^HM-^R; BaxM-bM-^HM-^R/M-bM-^HM-^R mice, DRGs were dissected and pooled from E14.5 NgfM-bM-^HM-^R/M-bM-^HM-^R; BaxM-bM-^HM-^R/M-bM-^HM-^R and BaxM-bM-^HM-^R/M-bM-^HM-^R embryos. Total RNA was extracted and directly subjected to microarray analysis. For the second screen comparing mouse DRG explants grown in the presence or absence of NGF, E13.5 mouse DRG explants were cultured for two days with 50 ng/ml of either NGF or NT3. Total RNA was extracted and then subjected to microarray analysis.
Project description:Comparison of transcript levels after diphtheria-toxin deletion of the Nav1.8-expressing cells using the cre/loxP system.<br> Pain requires input from nociceptors which are specialised peripheral sensory neurons in dorsal root ganglia (DRG). To explore the nociceptor-specific mRNA profiles, we used microarray analysis to examine the altered repertoire of genes expressed in DRG from mice depleted of Nav1.8-expressing neurons which are mainly nociceptors. To generate the animal, a Nav1.8 knock-in Cre-expressing mouse (Nav1.8-Cre) was used to excise a floxed stop upstream of globally expressed diphtheria toxin A-subunit gene (ROSA26-eGFP-DTA). By crossing heterozygous Cre mice with homozygous toxin-expressing floxed mice, experimental toxin-expressing (DTA) mice, in which DTA expressing nociceptors had been deleted, were generated. 6 DTA mice and 6 litter mate controls were used for microarray analysis. 3 Affymetrix Mouse Genome 430 2.0 Array chips were employed for analysis of the gene transcripts of each conditions.
Project description:We developed an approach to rapidly eliminate the subgroup of sensory neurons expressing the heat-gated cation channel TRPV1 from dissociated rat sensory ganglia using agonist treatment followed by density centrifugation. To identify transcripts predomintly expressed in TRPV1-positive neurons, we compared the transcriptome of all cells within sensory ganglia versus all cells without TRPV1 expressing neurons using RNA-Seq. Four replicate experiments with RNA from DRG neurons of one rat per experiment were performed. Dissociated neurons were split up in three parts, treated with solvent DMSO (0.1%), casaicin (10 µM), or RTX (100 nM) for 30 min followed by gradient centrifugation. RNA was extracted from the remaining pellet containing either all cells or all cells without TRPV1-positive neurons.
Project description:The goal of this study was to analyze global gene expression in specific populations of somatosensory neurons in the periphery, including major, non-overlapping populations that include nociceptors, pruriceptors, and prorioceptors. The mammalian somatosensory nervous system encodes the perception of specific environmental stimuli. The dorsal root ganglion (DRG) contains distinct somatosensory neuron subtypes that innervate diverse peripheral tissues, mediating the detection of thermal, mechanical, proprioceptive, pruriceptive, and nociceptive stimuli. We purified discrete subtypes of mouse DRG somatosensory neurons by flow cytometry using fluorescently labeled mouse lines (SNS-Cre/TdTomato, Parv-Cre/TdTomato) in combination with Isolectin B4-FITC surface staining (IB4). This allowed identification of transcriptional differences between these major populations, revealing enrichment of voltage-gated ion channels, TRP channels, G-protein coupled receptors, transcription factors, and other functionally important classes of genes within specific somatosensory neuron subsets. SNS-Cre mice were bred with Rosa26-TdTomato mice to generate SNS-Cre/TdTomato reporter mice. Parv-Cre mice were bred with Rosa26-TdTomato mice to generate Parv-Cre/TdTomato mice. Isolectin B4-FITC was used to stain the surface of SNS-Cre/TdTomato reporter mice. We used these strategies of fluorescent labeling to purify distinct murine sensory neuron subsets from the dorsal root ganglia (DRG) by fluorescence activated cell sorting (FACS). Neurons were sorted directly in Qiazol for total RNA extraction and microarray analysis. Whole DRG tissue was also included for transcriptome analysis to compare with purified neuronal populations.
Project description:Cultured adult mouse dorsal root ganglia (DRG) cells exhibit glial sensory progenitor properties in vitro. Therefore, they might be a good starter cell for reprogramming into sensory neurons. Here, we infected them with the retroviral vector Neurog2-Neurog1-DsRed to induce sensory neuron development and analyzed by scRNAseq at 14 days post infection whether infected cells show properties of sensory neurons such as nociceptors. After 10x Genomics, data analysis of 4,549 individual cells indicated the generation of neurons, but at an immature cell state.