Single-cell transcriptome profiling of the trigeminal ganglion of mice under normal and inflammatory pain conditions
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ABSTRACT: Orofacial inflammation could lead to transcriptional alterations in the trigeminal ganglion (TG). In this study, we performed single-cell RNA-sequencing (scRNA-seq) analysis of mouse TG to identify all cell types and profile transcriptomic alterations of TG cells under inflammatory conditions. A total of 7 types of cells including endothelial cells, fibroblasts, glial cells, granulocytes, lymphocytes, monocyte-macrophages and several subtypes of neurons were identified. In addition, we performed annotation of neuronal subtypes and differential gene expression analysis among TG neurons, identifying several differential genes involved in pain modulation such as Scn10a, Zbtb20 and Runx1. Collectively, our study revealed the heterogeneity of TG cells and diverse neuronal transcriptomic responses to orofacial inflammation, which aids in the development of novel therapeutics for orofacial inflammatory pain.
Project description:Peripheral sensory neurons in the dorsal root ganglion (DRG) and trigeminal ganglion (TG) are specialized to detect and transduce diverse environmental stimuli including touch, temperature, and pain to the central nervous system. Recent advances in single-cell RNA-sequencing (scRNA-seq) have provided new insights into the diversity of sensory ganglia cell types in rodents, non-human primates, and humans, but it remains difficult to compare transcriptomically defined cell types across studies and species. Here, we built cross-species harmonized atlases of DRG and TG cell types that describe 18 neuronal and 11 non-neuronal cell types across 6 species and 31 studies. We then demonstrate the utility of this harmonized reference atlas by using it to annotate newly profiled DRG nuclei/cells from both human and the highly regenerative axolotl. We observe that the transcriptomic profiles of sensory neuron subtypes are broadly similar across vertebrates, but the expression of functionally important neuropeptides and channels can vary notably. The new resources and data presented here can guide future studies in comparative transcriptomics, simplify cell type nomenclature differences across studies, and help prioritize targets for future analgesic development.
Project description:Trigeminal ganglion (TG) is the first station of sensory pathways in the orofacial region. The TG neurons communicate with satellite glial cells (SGCs), macrophages and other cells forming a functional unit that is responsible for processing of orofacial sensory information. Purinergic signaling, one of the most widespread autocrine and paracrine pathways, plays a crucial role in intercellular communication. The multidirectional action of purinergic signaling in different cell types contributes to the neuromodulation and orofacial sensation. To fully understand the purinergic signaling in these processes, it is essential to determine the shared and unique expression patterns of genes associated with purinergic signaling in different cell types. Here, we performed single-cell RNA sequencing of 22,969 cells isolated from normal mouse TGs. We identified 18 distinct cell populations, including 6 neuron subpopulations, 3 glial subpopulations, 7 immune cell subpopulations, fibroblasts, and endothelial cells. We also revealed the transcriptional features of genes associated with purinergic signaling, including purinergic receptors, extracellular adenosine triphosphate (eATP) release channels, eATP metabolism-associated enzymes, and eATP transporters) in each cell type. Our results have important implications for understanding and predicting the cell type-specific roles of the purinergic signaling in orofacial signal processing in the trigeminal primary sensory system.
Project description:Purpose: In this study, we aimed to analyze lncRNA expression in the whole transcriptome of trigeminal ganglia (TG) and spinal trigeminal nucleus caudalis (Sp5C) in a chronic inflammatory TMJ pain mouse model. Chronic inflammatory TMJ pain was induced by intra-TMJ injection of complete Freund's adjuvant (CFA). The lncRNA expression patterns in the whole transcriptome of TG and Sp5C were profiled with RNA sequencing.
Project description:SUMOylation is a dynamic post-translational protein modification that primarily takes place in cell nuclei, where it plays a key role in multiple DNA-related processes. In brain cells, and particularly in neurons, mostly nuclear proteins are SUMOylated, and the SUMOylation-dependent control of a subset of neuronal transcription factors is known to regulate various aspects of nerve cell differentiation, development, and function. In an unbiased screen for endogenous SUMOylation targets in the developing mouse brain, we previously identified the transcription factor Zbtb20 as a new SUMO1 conjugate. We show here that the three key SUMO paralogues SUMO1, SUMO2, and SUMO3 can all be conjugated to Zbtb20 in vitro, and we confirm the SUMOylation of Zbtb20 in vivo. Using primary hippocampal neurons as a model system, we then demonstrate that the expression of Zbtb20 is required for proper nerve cell development and neurite growth and branching. Furthermore, we show that the SUMOylation of Zbtb20 is essential for Zbtb20 function in this context, and provide evidence indicating that SUMOylation affects the Zbtb20-dependent transcriptional profile of neurons. Taken together, our data highlight the role of SUMOylation in the regulation of neuronal transcription factors that determine nerve cell development. Specifically, our data demonstrate that key functions of the transcription factor Zbtb20 in neuronal development and neurite growth are under the obligatory control of SUMOylation.
Project description:The mechanism of chronic orofacial pain was investigated by examining the interaction between activated microglia, C1q and neurons in RVM of rats with orofacial pain caused by temporomandibular joint injection of CFA. The results demonstrated that the pain threshold in CFA group exhibited a continuous decline, reaching its lowest point on the third day. During the modeling process, administered daily stereotactic injections of ANX-005 and minocycline into the RVM, which resulted in a notable recovery in the rats' pain threshold and a significant increase in C1q/C3 and microglia in RVM of CFA rat. The application of ANX-005 or minocycline resulted in a reduction in the expression of C1q/C3 and microglia. Notably, the expression of excitatory presynaptic membrane markers reduced and the length and density of dendritic spines decreased on neurons in RVM. Additionally, C1q was abundantly localized on excitatory presynaptic membranes and expressed in microglial lysosomes. Treatment with ANX-005 or minocycline resulted in a reduced number of immunofluorescence colocalizations and an elevated dendritic spine density. These findings indicate that initial orofacial pain induced by CFA, microglia in RVM are involved in the pruning of excitatory presynaptic membranes through the complement C1q/C3-CR3 signaling pathway. This process results in a reduction in the proportion of excitatory synapses and a disruption in the physiological balance between RVM descending facilitation and descending inhibition. This leads to the predominance of descending facilitation in pain transmission in the RVM, which in turn facilitates the chronification of orofacial pain.
Project description:The sensitization of trigeminal ganglion neurons contributes to primary headache disorders such as migraine, but the specific neuronal and non-neuronal trigeminal subtypes involved remain unclear. We thus developed a cell atlas in which human and mouse trigeminal ganglia are transcriptionally and epigenomically profiled at single-cell resolution. These data describe evolutionarily conserved and human-specific gene expression patterns within each trigeminal ganglion cell type, as well as the transcription factors and gene regulatory elements that contribute to cell-type-specific gene expression. We then leverage these data to identify trigeminal ganglion cell types that are implicated both by human genetic variation associated with migraine and two mouse models of headache. This trigeminal ganglion cell atlas improves our understanding of the cell types, genes, and epigenomic features involved in headache pathophysiology and establishes a rich resource of cell-type-specific molecular features to guide the development of more selective treatments for headache and facial pain.
Project description:We used RNA sequencing to screen differentially expressed genes (DEGs) in the rostral ventral medulla (RVM) and thalamus of rats during persistent orofacial pain to explore the mechanism of chronic orofacial pain.
Project description:Apical periodontitis (AP) is an inflammatory disease occurring following tooth infection with distinct osteolytic activity. Despite increasing evidence that sensory neurons participate in regulation of non-neuronal cells, their role in the development of AP is largely unknown. We hypothesized that Nav1.8+ nociceptors regulate bone metabolism changes in response to AP. Methods: A selective ablation of nociceptive neurons in Nav1.8Cre/ DTALox mouse line was used to evaluate the development and progression of AP using murine model of infection-induced AP. Micro-computed tomography examination was applied to quantify osteolytic lesions following induction of AP. Additionally, RT-PCR, RNAscope, and immunohistochemical (IHC) analysis were used to investigate the expression of immune cells, osteoblasts, and osteoclasts. Co-culture of trigeminal ganglia (TG) neurons from DTALox (control) and Nav1.8Cre/ DTALox mice with either IDG-SW3 or MC3T3-E1 osteoblast precursor cell lines or RAW264.7 murine macrophages were used to assess osteoblast and osteoclast function, by RNA sequencing, mineralization, and osteoclastic assays. Results: Ablation of Nav1.8+ nociceptors had earlier progression of AP with larger osteolytic lesions compared to the controls. IHC and RNAscope analysis demonstrated greater number of macrophages, T-cells, osteoclast and osteoblast precursors as well as an increased RANKL:OPG ratio at earlier time points among Nav1.8Cre/ DTALox mice. There was an increased expression of IL-1a and IL-6 within lesions of nociceptor-ablated mice. Further, co-culture experiments demonstrated that TG neurons promoted osteoblast mineralization and inhibited osteoclastic function. Conclusion: The findings suggest that TG Nav1.8+ neurons contribute to modulation of the AP development by delaying the influx of immune cells, promoting osteoblastic differentiation, and decreasing osteoclastic activities. This newly uncovered mechanism could become a therapeutic strategy for the treatment of AP and minimize the persistence of osteolytic lesions in refractory cases.
Project description:A major challenge in biology is to link cellular and molecular variations with behavioral phenotypes. Here, we approached this by studying somatosensory neurons from a panel of bird species from the family Anatidae, known for their tactile-based foraging behavior. We found that tactile specialists exhibit a proportional expansion of neuronal mechanoreceptors in trigeminal ganglia. The expansion of mechanoreceptors occurs via neurons with intermediately and slowly inactivating mechano-current. Such neurons contain the Piezo2 ion channel, whose expression positively correlates with the expression of factors responsible for the development and function of touch receptors. Conversely, Piezo2 expression negatively correlates with expression of molecules mediating the detection of temperature and pain, suggesting that the expansion of Piezo2-containing mechanoreceptors with prolonged mechano-current occurs at the expense of other types of sensory neurons. Our study reveals a general mechanism of tactile specialization in vertebrates at the level of somatosensory system.