GI highlights from the literature

Basic scienceFinding the niche for colonic stem cells

Degirmenci B, Valenta T, Dimitrieva S, et al. GLI1-expressing mesenchymal cells form the essential Wnt-secreting niche for colon stem cells. Nature 2018;558:449–453.

The intestinal stem cell niche is a collection of cells that supports the maintenance and self-renewal of stem cells. The Wnt signalling pathway is crucial for this process and Paneth cells residing at the crypt base provide Wnt ligands. Paneth cell loss though does not affect intestinal homeostasis and colonic crypts lack Paneth cells. This paper studies the role of Gli1+ mesenchymal cells surrounding crypts as niche components. Lineage tracing studies showed that Gli1+ cells are long-lived and act as progenitors, giving rise to differentiated mesenchymal cell types in vitro. Blocking Wnt secretion in Gli1+ cells in vivo led to crypt loss and intestinal breakdown at 21 days, accompanied by reduction in epithelial Wnt targets. Addition of...

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