Although the resultant phenotype was less profound than in the germline Vil1-Grem1 model, all Villin-CreERT2;Rosa26Grem1 animals developed polyposis with the initial establishment of ectopic crypts on the villi containing aberrantly proliferating Sox9(+) stem/progenitor cells (Fig. 1D). Here, GREM1 is linked to polyposis.