While adult intestinal stem cells and their niche are well characterised, their developmental specification is still poorly understood. In this issue of The EMBO Journal, Nigmatullina et al (2017) show that maturation of Lgr5+ progenitors in the small intestinal epithelium during murine embryonic development is controlled by the transcription factor Id2.
See also: L Nigmatullina et al
Maintenance of epithelial tissues is fuelled by adult stem cells, which reside in specialised niches. The stem cells of the small intestinal epithelium are located in the crypt bottom (Clevers, 2013). The maintenance of intestinal stem cells is controlled by the Wnt/β‐catenin signalling cascade. Consequently, Lgr5, both target gene and component of the Wnt/β‐catenin pathway, was discovered to be a marker of adult intestinal stem cells (Barker et al, 2007). However, the developmental origin of Lgr5+ intestinal stem cells and their specification during embryonic development remained unknown. It was suggested earlier that intestinal stem cells appear at embryonic day 14.5 (E14.5) during a developmental stage, when the epithelium reorganises by forming villi and inter‐villus regions (Guiu & Jensen, 2015). In contrast, it was subsequently reported that Lgr5 expression in the developing intestinal epithelium is initiated much earlier, that is at E12.5 (Shyer et al, 2015) during a phase of growth and elongation (Guiu & Jensen, 2015). It was also proposed that the pseudostratified intestinal epithelium is uniformly composed …
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