ORCID Profile
0000-0002-9701-8252
Current Organisation
University of Melbourne
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Autonomic Nervous System | Bioinformatics | Neurosciences
Expanding Knowledge in the Biological Sciences | Expanding Knowledge in the Medical and Health Sciences |
Publisher: Elsevier BV
Date: 09-2016
DOI: 10.1016/J.YDBIO.2016.05.030
Abstract: Co-ordinated gastrointestinal function is the result of integrated communication between the enteric nervous system (ENS) and "effector" cells in the gastrointestinal tract. Unlike smooth muscle cells, interstitial cells, and the vast majority of cell types residing in the mucosa, enteric neurons and glia are not generated within the gut. Instead, they arise from neural crest cells that migrate into and colonise the developing gastrointestinal tract. Although they are "later" arrivals into the developing gut, enteric neural crest-derived cells (ENCCs) respond to many of the same secreted signalling molecules as the "resident" epithelial and mesenchymal cells, and several factors that control the development of smooth muscle cells, interstitial cells and epithelial cells also regulate ENCCs. Much progress has been made towards understanding the migration of ENCCs along the gastrointestinal tract and their differentiation into neurons and glia. However, our understanding of how enteric neurons begin to communicate with each other and extend their neurites out of the developing plexus layers to innervate the various cell types lining the concentric layers of the gastrointestinal tract is only beginning. It is critical for postpartum survival that the gastrointestinal tract and its enteric circuitry are sufficiently mature to cope with the influx of nutrients and their absorption that occurs shortly after birth. Subsequently, colonisation of the gut by immune cells and microbiota during postnatal development has an important impact that determines the ultimate outline of the intrinsic neural networks of the gut. In this review, we describe the integrated development of the ENS and its target cells.
Publisher: American Physical Society (APS)
Date: 18-10-2019
Publisher: Springer New York
Date: 2019
DOI: 10.1007/978-1-4939-9412-0_8
Abstract: Time-lapse imaging of gut explants from embryonic mice in which neural crest-derived cells express fluorescent proteins allows the behavior of enteric neural crest cells to be observed and analyzed. Explants of embryonic gut are dissected, mounted on filter paper supports so the gut retains its tubular three-dimensional structure, and then placed in coverglass bottom culture dishes in tissue culture medium. A stainless steel ring is placed on top of the filter support to prevent movement. Imaging is performed using a confocal microscope in an environmental chamber. A z series of images through the network of fluorescent cells is collected every 3, 5, or 10 min. At the end of imaging, the z series are projected.
Publisher: MDPI AG
Date: 10-08-2022
DOI: 10.3390/BIOM12081101
Abstract: Hirschsprung disease (HSCR) is characterised by the absence of enteric ganglia along variable lengths of the distal bowel. Current gold standard treatment involves the surgical resection of the defective, aganglionic bowel. Clear and reliable distinction of the normoganglionated bowel from the transition zone is key for successful resection of the entire defective bowel, and the avoidance of subsequent postoperative complications. However, the intraoperative nature of the tissue analysis and the variability of patient s les, s le preparation, and operator objectivity, make reproducible identification of the transition zone difficult. Here, we have described a novel method for using muscle units as a distinctive landmark for quantifying the density of enteric ganglia in resection specimens from HSCR patients. We show that the muscle unit to ganglion ratio is greater in the transition zone when compared with the proximal, normoganglionated region for long-segment HSCR patients. Patients with short-segment HSCR were also investigated, however, the muscle unit to ganglion ratio was not significantly different in these patients. Immunohistochemical examination of in idual ganglia showed that there were no differences in the proportions of either enteric neurons or glial cells through the different regions of the resected colon. In addition, we identified that the size of enteric ganglia was smaller for patients that went on to develop HSCR associated enterocolitis although the density of ganglia, as determined by the muscle unit to ganglia ratio, was not different when compared with patients that had no further complications. This suggests that subtle changes in the enteric nervous system, even in the “normoganglionated” colon, could be involved in changes in immune function and subsequent bacterial dysbiosis.
Publisher: The Korean Society of Neurogastroenterology and Motility
Date: 07-2015
DOI: 10.5056/JNM15096
Publisher: Cold Spring Harbor Laboratory
Date: 20-01-2021
DOI: 10.1101/2021.01.19.427232
Abstract: Nutrient signals sensed by enteroendocrine cells are conveyed to the enteric nervous system (ENS) to initiate intestinal reflexes. We addressed whether there are specific enteric pathways dedicated to detecting different luminal nutrients. Calcium imaging was performed on intact jejunal preparations from Wnt1-cre R26R-GCaMP3 and Villin-cre R26R-GCaMP3 mice which express a fluorescent calcium indicator in their ENS or intestinal epithelium, respectively. Glucose, acetate, and L-phenylalanine were perfused onto the mucosa whilst imaging underlying enteric neurons. Nutrient transport or diffusion across the mucosa was mimicked by applying nutrients onto sensory nerve endings in a villus, or onto myenteric ganglia. The nutrients perfused onto the mucosa each elicited Ca 2+ transients in submucosal neurons and in distinct patterns of myenteric neurons. Notably, the neurochemical subtypes of myenteric neurons that responded differed between the nutrients, while submucosal responders were predominantly cholinergic. Nutrients applied into villi or onto ganglia did not elicit specific neuronal responses but did stimulate Ca 2+ signaling in the mucosal epithelium. These data suggest that nutrients are first detected at the level of the epithelium and that the ENS is capable of discriminating between different compositions of luminal content. Furthermore, our data show that responses to mucosal stimulation are primarily in the myenteric plexus and submucosal neurons respond secondarily.
Publisher: IOP Publishing
Date: 12-04-2017
Publisher: Springer Science and Business Media LLC
Date: 16-10-2017
DOI: 10.1038/NATURE24471
Abstract: On 17 August 2017, the Advanced LIGO and Virgo detectors observed the gravitational-wave event GW170817-a strong signal from the merger of a binary neutron-star system. Less than two seconds after the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source. This sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817 in both gravitational waves and electromagnetic waves represents the first 'multi-messenger' astronomical observation. Such observations enable GW170817 to be used as a 'standard siren' (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the Hubble constant. This quantity represents the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Here we report a measurement of the Hubble constant that combines the distance to the source inferred purely from the gravitational-wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. In contrast to previous measurements, ours does not require the use of a cosmic 'distance ladder': the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. We determine the Hubble constant to be about 70 kilometres per second per megaparsec. This value is consistent with existing measurements, while being completely independent of them. Additional standard siren measurements from future gravitational-wave sources will enable the Hubble constant to be constrained to high precision.
Publisher: MDPI AG
Date: 09-01-2023
DOI: 10.3390/BIOM13010139
Abstract: Glutamate is the major excitatory neurotransmitter in the central nervous system, and there is evidence that Group-I metabotropic glutamate receptors (mGlu1 and mGlu5) have established roles in excitatory neurotransmission and synaptic plasticity. While glutamate is abundantly present in the gut, it plays a smaller role in neurotransmission in the enteric nervous system. In this study, we examined the roles of Group-I mGlu receptors in gastrointestinal function. We investigated the expression of Grm1 (mGlu1) and Grm5 (mGlu5) in the mouse myenteric plexus using RNAscope in situ hybridization. Live calcium imaging and motility analysis were performed on ex vivo preparations of the mouse colon. mGlu5 was found to play a role in excitatory enteric neurotransmission, as electrically-evoked calcium transients were sensitive to the mGlu5 antagonist MPEP. However, inhibition of mGlu5 activity did not affect colonic motor complexes (CMCs). Instead, inhibition of mGlu1 using BAY 36-7620 reduced CMC frequency but did not affect enteric neurotransmission. These data highlight complex roles for Group-I mGlu receptors in myenteric neuron activity and colonic function.
Publisher: Elsevier BV
Date: 11-2022
Publisher: Springer International Publishing
Date: 2022
Publisher: Frontiers Media SA
Date: 17-01-2022
DOI: 10.3389/FCELL.2021.775102
Abstract: Enteric glia are a fascinating population of cells. Initially identified in the gut wall as the “support” cells of the enteric nervous system, studies over the past 20 years have unveiled a vast array of functions carried out by enteric glia. They mediate enteric nervous system signalling and play a vital role in the local regulation of gut functions. Enteric glial cells interact with other gastrointestinal cell types such as those of the epithelium and immune system to preserve homeostasis, and are perceptive to luminal content. Their functional versatility and phenotypic heterogeneity are mirrored by an extensive level of plasticity, illustrated by their reactivity in conditions associated with enteric nervous system dysfunction and disease. As one of the hallmarks of their plasticity and extending their operative relationship with enteric neurons, enteric glia also display neurogenic potential. In this review, we focus on the development of enteric glial cells, and the mechanisms behind their heterogeneity in the adult gut. In addition, we discuss what is currently known about the role of enteric glia as neural precursors in the enteric nervous system.
Publisher: eLife Sciences Publications, Ltd
Date: 04-02-2019
Publisher: Frontiers Media SA
Date: 2013
Publisher: Wiley
Date: 07-02-2019
DOI: 10.1002/GLIA.23596
Publisher: Springer Science and Business Media LLC
Date: 29-11-2017
DOI: 10.1038/NRGASTRO.2017.151
Abstract: Optogenetics and chemogenetics comprise a wide variety of applications in which genetically encoded actuators and indicators are used to modulate and monitor activity with high cellular specificity. Over the past 10 years, development of these genetically encoded tools has contributed tremendously to our understanding of integrated physiology. In concert with the continued refinement of probes, strategies to target transgene expression to specific cell types have also made much progress in the past 20 years. In addition, the successful implementation of optogenetic and chemogenetic techniques thrives thanks to ongoing advances in live imaging microscopy and optical technology. Although innovation of optogenetic and chemogenetic methods has been primarily driven by researchers studying the central nervous system, these techniques also hold great promise to boost research in neurogastroenterology. In this Review, we describe the different classes of tools that are currently available and give an overview of the strategies to target them to specific cell types in the gut wall. We discuss the possibilities and limitations of optogenetic and chemogenetic technology in the gut and provide an overview of their current use, with a focus on the enteric nervous system. Furthermore, we suggest some experiments that can advance our understanding of how the intrinsic and extrinsic neural networks of the gut control gastrointestinal function.
Publisher: eLife Sciences Publications, Ltd
Date: 12-02-2019
DOI: 10.7554/ELIFE.42914
Abstract: The enteric nervous system controls a variety of gastrointestinal functions including intestinal motility. The minimal neuronal circuit necessary to direct peristalsis is well-characterized but several intestinal regions display also other motility patterns for which the underlying circuits and connectivity schemes that coordinate the transition between those patterns are poorly understood. We investigated whether in regions with a richer palette of motility patterns, the underlying nerve circuits reflect this complexity. Using Ca2+ imaging, we determined the location and response fingerprint of large populations of enteric neurons upon focal network stimulation. Complemented by neuronal tracing and volumetric reconstructions of synaptic contacts, this shows that the multifunctional proximal colon requires specific additional circuit components as compared to the distal colon, where peristalsis is the predominant motility pattern. Our study reveals that motility control is hard-wired in the enteric neural networks and that circuit complexity matches the motor pattern portfolio of specific intestinal regions.
Publisher: Frontiers Media SA
Date: 23-02-2017
Publisher: Springer International Publishing
Date: 2016
DOI: 10.1007/978-3-319-27592-5_5
Abstract: All the neurons and glia of the enteric nervous system (ENS) arise from neural crest-derived cells that migrate into the gastrointestinal (GI) tract during development (Yntema and Hammond 1954 Le Douarin and Teillet 1973). Most of the ENS originates from vagal neural crest cells (NCCs), which arise from the caudal hindbrain region of the neural tube, adjacent to somites 1-7. In the developing mouse, vagal NCCs migrate into the developing oesophagus and stomach at embryonic day (E)9.5, enter the small intestine at E10.5, and colonise the developing GI tract in a rostral-to-caudal wave, reaching the anal end of the colon at E14.5 (Serbedzija et al. 1991 Kapur et al. 1992 Anderson et al. 2006). Recent evidence indicates that there is also trans-mesenteric migration of vagal NCCs, where some NCCs leave the small intestine and migrate directly across the mesentery into the colon (Nishiyama et al. 2012). Sacral NCCs also contribute to a small population of neurons and glia in the colon (Burns and Le Douarin 1998 Wang et al. 2011).
Publisher: Oxford University Press (OUP)
Date: 2022
DOI: 10.1093/BIOMETHODS/BPAC004
Abstract: Hirschsprung disease occurs when children are born with no intrinsic nerve cells in varying lengths of the large intestine. In the most severe cases, neurons are also missing from the distal part of the small intestine. Nerve-mediated relaxation of the aganglionic bowel fails and fecal matter accumulates in the more proximal regions of the intestine. This is life threatening. Perforation of the bowel can ensue, causing sepsis and in some cases, death of the infant. Repopulation of the colon with neural stem cells is a potential therapy, but for this to be successful the patient or experimental animal needs to survive long enough for neural precursors to differentiate and make appropriate connections. We have developed a surgical procedure that can be applied to rats with Hirschsprung disease. A stoma was created to allow the normal bowel to empty and a second stoma leading to the aganglionic bowel was also created. This allowed homozygous mutants that would usually die at less than 3 weeks of age to survive into adulthood. During this time, the rats also required post-operative care of their stomas. The interventions we describe provide an animal model of Hirschsprung disease that is suited to assess the effectiveness of cell therapies in the treatment of this condition.
Publisher: Cold Spring Harbor Laboratory
Date: 10-06-2021
DOI: 10.1101/2021.06.10.447700
Abstract: Monocyte-derived macrophages (Mφs) are crucial regulators during muscularis inflammation. However, it is unclear which microenvironmental factors are responsible for monocyte recruitment and neurotrophic Mφ differentiation in this paradigm. Here, we investigate Mφ heterogeneity at different stages of muscularis inflammation and determine how environmental cues can attract and activate tissue protective Mφs. Single cell RNA sequencing was performed on immune cells from the muscularis of wild-type and CCR2 -/- mice at different timepoints after muscularis inflammation. CX3CR1 GFP/+ and CX3CR1 CreERT2 R26 YFP mice were analyzed by flow cytometry and immunofluorescence. The transcriptome of enteric glial cells (EGCs) was investigated using PLP CreERT2 Rpl22 HA mice. In addition, we assessed the effect of supernatant from neurosphere-derived EGCs on monocyte differentiation based on the expression of pro- and anti-inflammatory factors. Muscularis inflammation induced marked alterations in mononuclear phagocyte populations associated with a rapid infiltration of Ly6c + monocytes that locally acquired unique transcriptional states. Trajectory inference analysis revealed two main pro-resolving Mφ subpopulations during the resolution of muscularis inflammation, i.e . Cd206 + MhcII hi and Timp2 + MhcII lo Mφs, which were both derived from CCR2 + monocytes. Interestingly, we found that EGCs were able to sense damage to the muscularis to stimulate monocyte recruitment and differentiation towards pro-resolving Mφs via CCL2 and CSF1, respectively. Our study provides a comprehensive insight into pro-resolving Mφ differentiation and their regulators during muscularis inflammation. We deepened our understanding in the interaction between EGCs and Mφs, thereby highlighting pro-resolving Mφ differentiation as a potential novel therapeutic strategy for the treatment of intestinal inflammation.
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1053/J.GASTRO.2017.01.005
Abstract: Cell therapy offers the potential to treat gastrointestinal motility disorders caused by diseased or absent enteric neurons. We examined whether neurons generated from transplanted enteric neural cells provide a functional innervation of bowel smooth muscle in mice. Enteric neural cells expressing the light-sensitive ion channel, channelrhodopsin, were isolated from the fetal or postnatal mouse bowel and transplanted into the distal colon of 3- to 4-week-old wild-type recipient mice. Intracellular electrophysiological recordings of responses to light stimulation of the transplanted cells were made from colonic smooth muscle cells in recipient mice. Electrical stimulation of endogenous enteric neurons was used as a control. The axons of graft-derived neurons formed a plexus in the circular muscle layer. Selective stimulation of graft-derived cells by light resulted in excitatory and inhibitory junction potentials, the electrical events underlying contraction and relaxation, respectively, in colonic muscle cells. Graft-derived excitatory and inhibitory motor neurons released the same neurotransmitters as endogenous motor neurons-acetylcholine and a combination of adenosine triphosphate and nitric oxide, respectively. Graft-derived neurons also included interneurons that provided synaptic inputs to motor neurons, but the pharmacologic properties of interneurons varied with the age of the donors from which enteric neural cells were obtained. Enteric neural cells transplanted into the bowel give rise to multiple functional types of neurons that integrate and provide a functional innervation of the smooth muscle of the bowel wall. Circuits composed of both motor neurons and interneurons were established, but the age at which cells are isolated influences the neurotransmitter phenotype of interneurons that are generated.
Publisher: American Physiological Society
Date: 10-2022
Abstract: Live calcium imaging is often used as a proxy for electrophysiological measurements and has been a valuable tool that allows simultaneous analysis of neuronal activity in multiple cells at the population level. In the enteric nervous system, there are two main electrophysiological classes of neurons, after-hyperpolarizing (AH)- and synaptic (S)-neurons, which have been shown to have different calcium handling mechanisms. However, they are rarely considered separately in calcium imaging experiments. A handful of studies have shown that in guinea pig, a calcium transient will accompany a single action potential in AH-neurons, but multiple action potentials are required to generate a calcium transient in S-neurons. How this translates to different modes of cellular depolarization and whether this is consistent across species is unknown. In this study, we used simultaneous whole-cell patch-cl electrophysiology together with calcium imaging to investigate how enteric neurons respond to different modes of depolarization. Using both traditional (4 Hz) and also high-speed (1,000 Hz) imaging techniques, we found that single action potentials elicit calcium transients in both AH-neurons and S-neurons. Subthreshold membrane depolarizations were also able to elicit calcium transients, although calcium responses were generally lified if an action potential was present. Furthermore, we identified that responses to nicotinic acetylcholine receptor stimulation can be used to distinguish between AH- and S-neurons in calcium imaging. NEW & NOTEWORTHY Live calcium imaging is an important tool for investigating enteric nervous system (ENS) function. Previous studies have shown that multiple action potentials are needed to generate a calcium response in S-neurons, which has important implications for the interpretation of calcium imaging data. Here, we show that in mouse myenteric neurons, calcium transients are elicited by single action potentials in both AH- and S-neurons. In addition, nicotinic acetylcholine receptor stimulation can be used to distinguish between these two classes.
Publisher: Springer International Publishing
Date: 2022
Publisher: American Physical Society (APS)
Date: 04-12-2019
Publisher: American Physical Society (APS)
Date: 20-11-2019
Publisher: Elsevier BV
Date: 08-2017
DOI: 10.1016/J.YDBIO.2017.05.018
Abstract: The enteric nervous system (ENS) is an extensive network of neurons in the gut wall that arises from neural crest-derived cells. Like other populations of neural crest cells, it is known that enteric neural crest-derived cells (ENCCs) influence the behaviour of each other and therefore must communicate. However, little is known about how ENCCs communicate with each other. In this study, we used Ca
Publisher: Elsevier BV
Date: 11-2019
DOI: 10.1016/J.YDBIO.2019.07.007
Abstract: Cells derived from the neural crest colonize the developing gut and give rise to the enteric nervous system. The rate at which the ENCC population advances along the bowel will be affected by both the speed and directionality of in idual ENCCs. The aim of the study was to use time-lapse imaging and pharmacological activators and inhibitors to examine the role of several intracellular signalling pathways in both the speed and the directionality of in idual enteric neural crest-derived cells in intact explants of E12.5 mouse gut. Drugs that activate or inhibit intracellular components proposed to be involved in GDNF-RET and EDN3-ETB signalling in ENCCs were used. Pharmacological inhibition of JNK significantly reduced ENCC speed but did not affect ENCC directionality. MEK inhibition did not affect ENCC speed or directionality. Pharmacological activation of adenylyl cyclase or PKA (a downstream cAMP-dependent kinase) resulted in a significant decrease in ENCC speed and an increase in caudal directionality of ENCCs. In addition, adenylyl cyclase activation also resulted in reduced cell-cell contact between ENCCs, however this was not observed following PKA activation, suggesting that the effects of cAMP on adhesion are not mediated by PKA. JNK is required for normal ENCC migration speed, but not directionality, while cAMP signalling appears to regulate ENCC migration speed, directionality and adhesion. Collectively, our data demonstrate that intracellular signalling pathways can differentially affect the speed and directionality of migrating ENCCs.
Publisher: Springer Science and Business Media LLC
Date: 14-12-2022
Publisher: Elsevier
Date: 2018
Publisher: American Physiological Society
Date: 2020
Abstract: Detection of nutritional and noxious food components in the gut is a crucial component of gastrointestinal function. Contents in the gut lumen interact with enteroendocrine cells dispersed throughout the gut epithelium. Enteroendocrine cells release many different hormones, neuropeptides, and neurotransmitters that communicate either directly or indirectly with the central nervous system and the enteric nervous system, a network of neurons and glia located within the gut wall. Several populations of enteric neurons extend processes that innervate the gastrointestinal lamina propria however, how these processes develop and begin to transmit information from the mucosa is not fully understood. In this study, we found that Tuj1-immunoreactive neurites begin to project out of the myenteric plexus at embryonic day (E)13.5 in the mouse small intestine, even before the formation of villi. Using live calcium imaging, we discovered that neurites were capable of transmitting electrical information from stimulated villi to the plexus by E15.5. In unpeeled gut preparations where all layers were left intact, we also mimicked the basolateral release of 5-HT from enteroendocrine cells, which triggered responses in myenteric cell bodies at postnatal day (P)0. Altogether, our results show that enteric neurons extend neurites out of the myenteric plexus early during mouse enteric nervous system development, innervating the gastrointestinal mucosa, even before villus formation in mice of either sex. Neurites are already able to conduct electrical information at E15.5, and responses to 5-HT develop postnatally. NEW & NOTEWORTHY How enteric neurons project into the gut mucosa and begin to communicate with the epithelium during development is not known. Our study shows that enteric neurites project into the lamina propria as early as E13.5 in the mouse, before development of the submucous plexus and before formation of intestinal villi. These neurites are capable of transmitting electrical signals back to their cell bodies by E15.5 and respond to serotonin applied to neurite terminals by birth.
Publisher: Elsevier BV
Date: 07-2023
Start Date: 2019
End Date: 2021
Funder: Australian Research Council
View Funded ActivityStart Date: 2014
End Date: 2018
Funder: National Health and Medical Research Council
View Funded ActivityStart Date: 11-2019
End Date: 01-2023
Amount: $390,000.00
Funder: Australian Research Council
View Funded Activity