<i>Atg14</i> protects the intestinal epithelium from TNF-triggered villus atrophy

Regulation of intestinal epithelial turnover is a key component of villus maintenance in the intestine. The balance of cell turnover can be perturbed by various extrinsic factors including the cytokine TNF, a cell signaling protein that mediates both proliferative and cytotoxic outcomes. Under conditions of infection and damage, defects in autophagy are associated with TNF-mediated cell death and tissue damage in the intestinal epithelium. However, a direct role of autophagy within the context of enterocyte cell death during homeostasis is lacking. Here, we generated mice lacking ATG14 (autophagy related 14) within the intestinal epithelium [<i>Atg14^f/f Vil1-</i>Cre (<i>VC</i>)<i>⁺</i>]. These mice developed spontaneous villus loss and intestinal epithelial cell death within the small intestine. Based on marker studies, the increased cell death in these mice was due to apoptosis. <i>Atg14^f/f VC⁺</i> intestinal epithelial cells demonstrated sensitivity to TNF-triggered apoptosis. Correspondingly, both TNF blocking antibody and genetic deletion of <i>Tnfrsf1a/Tnfr1</i> rescued villus loss and cell death phenotype in <i>Atg14^f/f VC⁺</i> mice. Lastly, we identified a similar pattern of spontaneous villus atrophy and cell death when <i>Rb1cc1</i>/<i>Fip200</i> was conditionally deleted from the intestinal epithelium (<i>Rb1cc1^f/f VC⁺</i>). Overall, these findings are consistent with the hypothesis that factors that control entry into the autophagy pathway are also required during homeostasis to prevent TNF triggered death in the intestine. <b>Abbreviations:</b> ANOVA: analysis of variance; <i>Atg14</i>: autophagy related 14; <i>Atg16l1</i>: autophagy related 16-like 1 (S. cerevisiae); <i>Atg5</i>: autophagy related 5; cCASP3: cleaved CASP3/caspase-3; cCASP8: cleaved CASP8/caspase-8; CHX: cycloheximide; EdU: 5-ethynyl-2´-deoxyuridine thymidine; f/f: flox/flox; H&amp;E: hematoxylin and eosin; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; Nec-1: necrostatin-1; <i>Rb1cc1/Fip200</i>: RB1-inducible coiled-coil 1; <i>Ripk1</i>: receptor (TNFRSF)-interacting serine-threonine kinase 1; <i>Ripk3</i>: receptor (TNFRSF)-interacting serine-threonine kinase 3; <i>Tnfrsf1a/Tnfr1</i>: tumor necrosis factor receptor superfamily, member 1a; <i>Tnf/ Tnfsf1a</i>: tumor necrosis factor; VC: <i>Vil1/villin 1</i>-Cre