Project description:Background & Aims: Visceral hypersensitivity, a hallmark of irritable bowel syndrome, is generally considered to be mechanosensitive in nature and mediated via spinal afferents. Both stress and inflammation are implicated in visceral hypersensitivity, but the underlying molecular mechanisms of visceral hypersensitivity are unknown. <br> Methods: Mice were infected with Nippostrongylus brasiliensis (Nb) larvae, exposed to environmental stress and the following separate studies performed 3-4 weeks later. Mesenteric afferent nerve activity was recorded in response to either ramp balloon distension (60 mmHg), or to an intraluminal perfusion of hydrochloric acid (50 mM), or to octreotide administration (2 µM). Intraperitoneal injection of cholera toxin B-488 identified neurons projecting to the abdominal viscera. Fluorescent neurons in dorsal root and nodose ganglia were isolated using laser-capture microdissection. RNA was hybridised to Affymetrix Mouse whole genome arrays for analysis to evaluate the effects of stress and infection. <br> Results: In mice previously infected with Nb, there was no change in intestinal afferent mechanosensitivity, but there was an increase in chemosensitive responses to intraluminal hydrochloric acid when compared to control animals. Gene expression profiles in vagal but not spinal visceral sensory neurons were significantly altered in stressed Nb-infected mice. Decreased afferent responses to somatostatin receptor 2 stimulation correlated with lower expression of vagal somatostatin receptor 2 in stressed Nb-infected mice, confirming a link between molecular data and functional sequelae. <br> Conclusions: Alterations in the intestinal brain-gut axis, in chemosensitivity but not mechanosensitivity, and through vagal rather than spinal pathways, are implicated in stress-induced post-inflammatory visceral hypersensitivity.
Project description:Vagal sensory neurons (VSNs) located in the nodose ganglion provide information, such as stomach stretch or the presence of ingested nutrients, to the caudal medulla via specialized cell types expressing unique marker genes. Here, we leverage VSN marker genes identified in adult mice to determine when specialized vagal subtypes arise developmentally and the trophic factors that shape their growth. Experiments to screen for trophic factor sensitivity revealed that brain derived neurotrophic factor (BDNF) and glial cell derived neurotrophic factor (GDNF) robustly stimulate neurite outgrowth from VSNs in vitro. Perinatally, BDNF was expressed by neurons of the nodose ganglion itself, while GDNF was expressed by intestinal smooth muscle cells. Thus, BDNF may support VSNs locally, whereas GDNF may act as a target-derived trophic factor supporting the growth of processes at distal innervation sites in the gut. Consistent with this, expression of the GDNF receptor was enriched in VSN cell types that project to the gastrointestinal tract. Lastly, mapping of genetic markers in the nodose ganglion demonstrates that defined vagal cell types begin to emerge as early as embryonic day 13, even as VSNs continue to grow to reach gastrointestinal targets. Despite the early onset of expression for some marker genes, expression patterns of many cell type markers appear immature in prenatal life and mature considerably by the end of the first postnatal week. Together, the data support location-specific roles for BDNF and GDNF in stimulating VSN growth, and a prolonged perinatal timeline for VSN maturation in male and female mice.
Project description:Vagal afferent neurons are thought to convey primarily physiological information, whereas spinal afferents transmit noxious signals from the viscera to the central nervous system. In order to elucidate molecular identities for these different properties, we compared gene expression profiles of neurons located in nodose ganglia (NG) and dorsal root ganglia (DRG) in mice. Intraperitoneal administration of Alexa Fluor-488 conjugated Cholera toxin B allowed identification of neurons projecting to the viscera. Fluorescent neurons in DRG (from T10 to T13) and NG were isolated using laser capture microdissection. Gene expression profiles of visceral afferent neurons, obtained by microarray hybridization, were analysed using multivariate spectral map analysis, SAM algorithm (Significance Analysis of Microarray data) and fold-difference filtering. A total of 1996 genes were found to be differentially expressed in DRG versus NG, including 41 G-protein coupled receptors and 60 ion channels. Expression profiles obtained on laser-captured neurons were contrasted to those obtained on whole ganglia demonstrating striking differences and the need for microdissection when studying visceral sensory neurons because of dilution of the signal by somatic sensory neurons. Furthermore, a detailed catalogue of all adrenergic and cholinergic, GABA, glutamate, serotonin and dopamine receptors, voltage-gated potassium, sodium and calcium channels and transient receptor potential cation channels present in visceral afferents is provided. Our genome-wide expression profiling data provide novel insight into molecular signatures that underlie both functional differences and similarities between NG and DRG visceral sensory neurons. Moreover, these findings will offer novel insight into mode of action of pharmacologic agents modulating visceral sensation. Experiment Overall Design: Three separate experiments were performed. First, 5 whole dorsal root ganglia were compared to 7 whole nodose ganglia. Second, Laser captured visceral neurons derived from 5 dorsal root ganglia and 5 nodose ganglia were compared on MG-U74Av2. Third, Laser captured visceral neurons derived from 9 dorsal root ganglia and 11 nodose ganglia were compared on Mouse430_2.
Project description:Sensory functions of the vagus nerve are critical for specific aware perceptions and for monitoring visceral functions in the cardio-pulmonary and gastrointestinal systems. Here we present a comprehensive identification, classification, and validation of the neuron types in the neural crest (jugular) and placode (nodose) derived vagal ganglia by single cell transcriptomic (scRNA-seq) analysis. Our results reveal major differences between neurons derived from different embryonic origins. Jugular neurons exhibit fundamental similarities to the somatosensory spinal neurons, including major types such as C-low threshold mechanoreceptors (C-LTMRs), A-LTMRs, Aδ-nociceptors, cold-, and mechano-heat C-nociceptors. In contrast, the nodose ganglion contains 18 distinct types dedicated to surveying the physiological state of the internal body. Our results reveal a vast diversity of vagal neuron types including many previously unanticipated types as well as proposed types that are consistent with chemoreceptors, nutrient detectors, baroreceptors, and stretch and volume mechanoreceptors of the respiratory, gastrointestinal, and cardiovascular systems.
Project description:Capsaicin-sensitive (Trpv1-positive) sensory C-fibers derived from vagal ganglia innervate the visceral organs, and respond to inflammatory mediators and noxious stimuli. These neurons play an important role in maintenance of visceral homeostasis, and contribute to the symptoms of visceral inflammatory diseases. Vagal sensory neurons are located in two ganglia, the jugular ganglia (derived from the neural crest), and the nodose ganglia (from the epibranchial placodes). The functional difference, especially in response to immune mediators, between jugular and nodose neurons is not fully understood. In this study, we microscopically isolated murine nodose and jugular capsaicin-sensitive / Trpv1-expressing C-fiber neurons and performed transcriptome profiling using ultra-low input RNA sequencing.
Project description:Analysis of gene expression regulated by PPARγ in the nodose ganglion of Phox2b::Cre; PPARγ fl/+ and Phox2b::Cre; PPARγ fl/fl mice. Resutls demonstrate potential PPARγ transcriptional targets in neurons RNA was purified from laser-captured nodose neurons. Three independent biological replicates were prepared by pooling RNA of nodose neurons from multiple animals of the same genotypes. Genomics and Microarray Core Facility at UT Southwestern ( http://microarray.swmed.edu/) checked RNA quality and performed the hybridization with a Mouse-6 V2 BeadChip (Illumina Inc.). We used Partek Genomics Suite 6.5 (Partek Inc.) and Ingenuity Pathway Analysis (Ingenuity Systems Inc.) for data and pathway analysis respectively.
Project description:The vagus nerve has long been associated with the regulation of energy balance. However, the identity of the molecules mediating these effects remain largely unknown. Here, we used RNA sequencing to interrogate the molecular repertoire of the mouse vagal afferents. We found that Fgf3 mRNA is upregulated in the jugular-nodose ganglia under acute insulin resistance. Together, we provide evidence for efferent-like roles of the vagal afferents and identify Fgf3 as a novel vagal sensory-derived metabolic hormone that regulates insulin secretion and energy expenditure.
Project description:Analysis of gene expression regulated by PPARγ in the nodose ganglion of Phox2b::Cre; PPARγ fl/+ and Phox2b::Cre; PPARγ fl/fl mice. Resutls demonstrate potential PPARγ transcriptional targets in neurons
Project description:Mammalian airways and lungs are richly innervated by bronchopulmonary sensory neurons, the vast majority of which are derived from the vagal sensory ganglia. In the present study we set out to perform high coverage single cell RNA sequencing on a population of identified murine bronchopulmonary sensory neurons collected from the vagal sensory ganglia to better define the molecular expression profiles of these cell types. Given the importance of P2X2 in differentiating nodose from jugular sensory neurons, we further aimed to investigate the relationship between transcriptional expression of identified genes and P2X2 expression.
Project description:Guided by gut sensory cues, humans and animals prefer nutritive sugars over non-caloric sweeteners. But how the gut differentiates such stimuli to rapidly guide preferences remains unknown. In the intestine, innervated enteroendocrine cells synapse with the vagus nerve to convey luminal sugar stimuli to the brain within seconds. Here, we sequenced individual vagal nodose neuron cells from the left and right nodose to assess their relative contribution to sugar signaling from the gut. The neurons lack expression of sugar receptors and transporters, but do express receptors for neurotransmitters and neuropeptides secreted by intestinal sensory epithelial cells.