Intestinal epithelial ZO-2 is critical for downregulation of injury-induced proliferation after mucosal repair is complete

Zonula occludens-2 (ZO-2), encoded by TJP2, is a multi-domain scaffolding protein that recruits claudin proteins to tight junctions. In MDCK cells, Tjp2 knockdown inhibits Hippo signaling pathway and activates Yap/Taz. In humans, TJP2 mutations within the region that mediates claudin binding are associated with cholestasis that is exacerbated by defects in bile acid conjugation. Similarly, liver-specific Tjp2 knockout mice are phenotypically normal but hypersensitive to bile-acid induced cholestatic disease. We sought to determine whether ZO-2 has similar protective functions in intestinal epithelia. Like humans with TJP2 mutations, intestinal epithelial-specific Tjp2-knockout in mice did not induce spontaneous gut disease. There was, however, increased epithelial proliferation, mucosal hyperplasia, and Yap/Taz activation. Nuclear activated Yap was increased 1.9±0.1-fold in Tjp2 knockout enterocytes relative to wild type. In hepatocytes, bile acid stress elicited liver disease. We therefore asked if intestinal epithelial Tjp2 knockout increased mucosal injury induced by systemic T cell activation, TLR3 activation (poly I:C injection), or irradiation. In contrast to hepatocytes lacking ZO-2, intestinal epithelial ZO-2 deletion accelerated proliferation and repair. However, unlike wildtype mice, intestinal epithelial proliferation remained increased in Tjp2 knockout mice after repair was complete and mitotic activity had returned to baseline in wildtype mice. This phenotype is intrinsic to epithelial cells, as Tjp2 knockout enteroids excessive proliferation and formed complex cysts with exuberant budding. These data indicate that ZO-2 is a critical regulator of proliferative homeostasis within the intestinal epithelium and suggest that ZO-2 loss may contribute to dysregulated growth of intestinal neoplasms. Supported by: National Institutes of Health grants R01DK61931 and R01DK068271 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.