BMP pathway antagonism by Grem1 regulates epithelial cell fate in intestinal regeneration
In the intestine, the homeostatic effect of Bone Morphogenetic Protein (BMP) on cell fate has predominantly been inferred through pathway inactivation. Here, we assessed the impact of autocrine Bmp4 expression on secretory cell fate. Ligand exposure reduced proliferation, expedited terminal differentiation, abrogated long-term secretory cell survival and prevented dedifferentiation. As stem cell plasticity is required for regenerative adaptive reprogramming, we spatiotemporally mapped and functionally explored BMPs role in epithelial restitution. Following ulceration, physiological attenuation of BMP signalling arose through upregulation of the secreted antagonist, Grem1, from topographically distinct populations of stromal cells. Concomitant expression supported functional compensation, following Grem1 deletion from tissue-resident fibroblasts. BMP pathway manipulation showed that antagonist-mediated BMP attenuation was obligatory, but functionally sub-maximal, as regeneration was impaired or enhanced by epithelial overexpression of Bmp4 or Grem1 respectively. Mechanistically, Bmp4 abrogated regenerative stem cell reprogramming, despite a convergent impact of YAP/TAZ on cell fate in remodelled wounds.