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Single cell and genetic analyses reveal conserved populations and signaling mechanisms of gastrointestinal stromal niches.

ABSTRACT: Stomach and intestinal stem cells are located in discrete niches called the isthmus and crypt, respectively. Recent studies have demonstrated a surprisingly conserved role for Wnt signaling in gastrointestinal development. Although intestinal stromal cells secrete Wnt ligands to promote stem cell renewal, the source of stomach Wnt ligands is still unclear. Here, by performing single cell analysis, we identify gastrointestinal stromal cell populations with transcriptome signatures that are conserved between the stomach and intestine. In close proximity to epithelial cells, these perictye-like cells highly express telocyte and pericyte markers as well as Wnt ligands, and they are enriched for Hh signaling. By analyzing mice activated for Hh signaling, we show a conserved mechanism of GLI2 activation of Wnt ligands. Moreover, genetic inhibition of Wnt secretion in perictye-like stromal cells or stromal cells more broadly demonstrates their essential roles in gastrointestinal regeneration and development, respectively, highlighting a redundancy in gastrointestinal stem cell niches.

SUBMITTER: Kim JE

PROVIDER: S-EPMC6969052 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Stomach and intestinal epithelial cells are maintained by the activity of stem cells located in the isthmus and crypt, respectively1,2. Recent studies have demonstrated a surprisingly conserved role for Wnt signaling in stomach and intestinal development and stem cells3,4. Although accumulating evidence suggests that intestinal stromal cells secrete Wnt ligands to promote stem cell renewal5-10, the source of stomach Wnt ligands is still unclear. Moreover, how these gastrointestinal stem cell niche signals are produced is currently unknown. By performing single cell analysis of gastrointestinal stromal cells, we identified cell populations with transcriptome signatures that are conserved between the stomach and intestine. In close proximity to gastrointestinal epithelial cells, these cells highly expressed pericyte markers and Wnt ligands. They also were enriched for Hh signaling, which plays a key role in gut development11,12. A recent study has shown that intestinal pericryptal cells co-express Hh target and Wnt ligand genes8. To define their relationship, we analyzed mice with Hh gain of function in the pericyte-like stromal cells conserved between the stomach and intestine, and found increased levels of Wnt ligands, supporting Hh regulation of stromal Wnt ligand expression. Moreover, utilizing Sufu and Spop double knockout mice, which stabilized GLI2, a key Hh mediator in the gut, we were able to map GLI2 binding sites genome-wide and analyze super enhancers. This work demonstrates GLI2 activation of stromal Wnt ligands through enhancers that are conserved between the stomach and intestine. To determine the significance of Wnt secreting gastrointestinal stromal cells, we genetically inhibited Wnt secretion from the perictye-like or broad stromal cells, demonstrating their roles in gastrointestinal regeneration and development, respectively. Our work not only identifies the conserved gastrointestinal stromal niche cell populations but also reveals their underlying signaling and epigenetic mechanisms.

Project description:The mammalian brain contains numerous neurons distributed across forebrain, midbrain, and hindbrain that project axons to the lower spinal cord and work in concert to control movement and achieve homeostasis. Extensive work has mapped the anatomic location of supraspinal cell types and continues to establish specific physiological functions. The patterns of gene expression that typify and distinguish these disparate populations, however, are mostly unknown. Here, using adult mice of mixed sex, we combined retrograde labeling of supraspinal cell nuclei with fluorescence-activated nuclei sorting and single-nuclei RNA sequencing analyses to transcriptionally profile neurons that project axons from the brain to lumbar spinal cord. We identified 14 transcriptionally distinct cell types and used a combination of established and newly identified marker genes to assign an anatomic location to each. To validate the putative marker genes, we visualized selected transcripts and confirmed selective expression within lumbar-projecting neurons in discrete supraspinal regions. Finally, we illustrate the potential utility of these data by examining the expression of transcription factors that distinguish different supraspinal cell types and by surveying the expression of receptors for growth and guidance cues that may be present in the spinal cord. Collectively, these data establish transcriptional differences between anatomically defined supraspinal populations, identify a new set of marker genes of use in future experiments, and provide insight into potential differences in cellular and physiological activity across the supraspinal connectome.SIGNIFICANCE STATEMENT The brain communicates with the body through a wide variety of neuronal populations with distinct functions and differential sensitivity to damage and disease. We have used single-nuclei RNA sequencing technology to distinguish patterns of gene expression within a diverse set of neurons that project axons from the mouse brain to the lumbar spinal cord. The results reveal transcriptional differences between populations previously defined on the basis of anatomy, provide new marker genes to facilitate rapid identification of cell type in future work, and suggest distinct responsiveness of different supraspinal populations to external growth and guidance cues.

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Single cell and genetic analyses reveal conserved populations and signaling mechanisms of gastrointestinal stromal niches.

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