SMN1 and inflammatory bowel disease: Gut mesenchymal populations include ISEMFs, which are smooth muscle α-ACTIN–positive (SMA-positive), vimentin-positive, and desmin-negative cells that express epimorphin, a myofibroblast protein that regulates growth factor secretion (15, 16); and FOXL1+ telocytes, which also have been shown to play a role in the stem cell niche in mouse models and in human inflammatory bowel disease (13).