A branching model of lineage differentiation underpinning the neurogenic potential of enteric glia.

Glial cells have been proposed as a source of neural progenitors, but the mechanisms underpinning the neurogenic potential of adult glia are not known. Using single cell transcriptomic profiling, we show that enteric glial cells represent a cell state attained by autonomic neural crest cells as they transition along a linear differentiation trajectory that allows them to retain neurogenic potential while acquiring mature glial functions. Key neurogenic loci in early enteric nervous system progenitors remain in open chromatin configuration in mature enteric glia, thus facilitating neuronal differentiation under appropriate conditions. Molecular profiling and gene targeting of enteric glial cells in a cell culture model of enteric neurogenesis and a gut injury model demonstrate that neuronal differentiation of glia is driven by transcriptional programs employed in vivo by early progenitors. Our work provides mechanistic insight into the regulatory landscape underpinning the development of intestinal neural circuits and generates a platform for advancing glial cells as therapeutic agents for the treatment of neural deficits.

Regulation of intestinal immunity and tissue repair by enteric glia.

Tissue maintenance and repair depend on the integrated activity of multiple cell types1. Whereas the contributions of epithelial2,3, immune4,5 and stromal cells6,7 in intestinal tissue integrity are well understood, the role of intrinsic neuroglia networks remains largely unknown. Here we uncover important roles of enteric glial cells (EGCs) in intestinal homeostasis, immunity and tissue repair. We demonstrate that infection of mice with Heligmosomoides polygyrus leads to enteric gliosis and the upregulation of an interferon gamma (IFNγ) gene signature. IFNγ-dependent gene modules were also induced in EGCs from patients with inflammatory bowel disease8. Single-cell transcriptomics analysis of the tunica muscularis showed that glia-specific abrogation of IFNγ signalling leads to tissue-wide activation of pro-inflammatory transcriptional programs. Furthermore, disruption of the IFNγ-EGC signalling axis enhanced the inflammatory and granulomatous response of the tunica muscularis to helminths. Mechanistically, we show that the upregulation of Cxcl10 is an early immediate response of EGCs to IFNγ signalling and provide evidence that this chemokine and the downstream amplification of IFNγ signalling in the tunica muscularis are required for a measured inflammatory response to helminths and resolution of the granulomatous pathology. Our study demonstrates that IFNγ signalling in enteric glia is central to intestinal homeostasis and reveals critical roles of the IFNγ-EGC-CXCL10 axis in immune response and tissue repair after infectious challenge.

Enteric Nervous System: lessons from neurogenesis for reverse engineering and disease modelling and treatment.

Normal activity and functional integration of the enteric nervous system (ENS) into the gut tissue circuitry and the luminal ecosystem are essential for digestive physiology and human health. A range of debilitating gastrointestinal disorders are linked to ENS dysfunction, caused either by developmental deficits, such as congenital megacolon (Hirschsprung's disease-HSCR) or a host of acquired intestinal neuropathies with unclear molecular or cellular pathogenesis. Recent advances in cell engineering underscore the potential use of cell replacement technologies for the treatment of ENS disorders. This review will highlight strategies used to derive ENS lineages from various tissue sources intended for cell therapy and disease modelling. We will also describe how a developmental atlas of the mammalian ENS re-constructed from single cell genomics data is an essential reference for shaping future therapeutic approaches in regenerative enteric neuroscience and neuro-gastroenterology.

Ablating the aryl hydrocarbon receptor (AhR) in CD11c+ cells perturbs intestinal epithelium development and intestinal immunity.

Diet and microbiome derived indole derivatives are known to activate the ligand induced transcription factor, the Aryl hydrocarbon Receptor (AhR). While the current understanding of AhR biology has confirmed its role in mucosal lymphocytes, its function in intestinal antigen presenting cells (APCs) is poorly understood. Here, we report that Cre-mediated deletion of AhR in CD11c-expressing cells in C57/BL6 mice is associated with altered intestinal epithelial morphogenesis in vivo. Moreover, when co-cultured with AhR-deficient DCs ex vivo, intestinal organoids showed reduced SRY (sex determining region Y)-box 9 and increased Mucin 2 expression, which correlates with reduced Paneth cells and increased goblet cell differentiation, similar to the data obtained in vivo. Further, characterization of intestinal APC subsets, devoid of AhR, revealed an expression pattern associated with aberrant intrinsic Wnt pathway regulation. At a functional level, the loss of AhR in APCs resulted in a dysfunctional epithelial barrier, associated with a more aggressive chemically induced colitis compared to wild type animals. Our results are consistent with a model whereby the AhR signalling pathway may participate in the regulation of innate immunity through intestinal epithelium development and mucosal immunity.

The gut microbiota keeps enteric glial cells on the move; prospective roles of the gut epithelium and immune system.

The enteric nervous system (ENS) coordinates the major functions of the gastrointestinal tract. Its development takes place within a constantly changing environment which, after birth, culminates in the establishment of a complex gut microbiota. How such changes affect ENS development and its subsequent function throughout life is an emerging field of study that holds great interest but which is inadequately explored thus far. In this addendum, we discuss our recent findings showing that a component of the ENS, the enteric glial cell network that resides in the gut lamina propria, develops after birth and parallels the evolution of the gut microbiota. Importantly, this network was found to be malleable throughout life by incorporating new cells that arrive from the area of the gut wall in a process of directional movement which was controlled by the lumen gut microbiota. Finally, we postulate on the roles of the intestinal epithelium and the immune system as potential intermediaries between gut microbiota and ENS responses.

Microbiota controls the homeostasis of glial cells in the gut lamina propria.

The intrinsic neural networks of the gastrointestinal tract are derived from dedicated neural crest progenitors that colonize the gut during embryogenesis and give rise to enteric neurons and glia. Here, we study how an essential subpopulation of enteric glial cells (EGCs) residing within the intestinal mucosa is integrated into the dynamic microenvironment of the alimentary tract. We find that under normal conditions colonization of the lamina propria by glial cells commences during early postnatal stages but reaches steady-state levels after weaning. By employing genetic lineage tracing, we provide evidence that in adult mice the network of mucosal EGCs is continuously renewed by incoming glial cells originating in the plexi of the gut wall. Finally, we demonstrate that both the initial colonization and homeostasis of glial cells in the intestinal mucosa are regulated by the indigenous gut microbiota.