A YAP1-DDIT4-NME1 Axis in Paligenosis

Paligenosis is an evolutionarily conserved process that cells undergo in response to injury or stress, which can result in cancer when dysregulated. We have established an in vivo model using high-dose tamoxifen (HDT) intraperitoneal injections to induce paligenosis in mouse gastric chief cells. Paligenosis follows a stepwise process: In stage 1, the chief cells undergo autodegradation downscaling with decreased mTORC1 activity; in stage 2, reprogramming of cells into a more progenitor-like state occurs with expression of embryonic and metaplastic genes; in stage 3, reentry into the cell cycle occurs in which mTORC1 activity returns. We have identified key proteins that play critical roles in regulating this process, including DDIT4 which increases in stage 1 and functions as the initial suppressor of mTORC1. As paligenosis progresses and DDIT4 decreases, p53 maintains mTORC1 suppression throughout stage 2 until IFRD1 licenses cell cycle reentry via p53 suppression in the transition to stage 3. However, the underlying mechanism behind the reduction of DDIT4 in stages 2 and 3 remains unclear. Our preliminary data indicate that the Hippo pathway effector YAP1 is activated during stage 1 and facilitates the transition from stage 1 to stage 2. Previous research has identified YAP1 as a transcriptional repressor of DDIT4, thus we hypothesize that YAP1 activation suppresses DDIT4 in later stages of paligenosis. Using a Cre-recombinase-inducible, constitutively active YAP1 mutant (LSL- Yap S112A ) driven by a chief cell-specific Cre, we observed the loss of DDIT4 in chief cells by immunohistochemistry (IHC). Enrichment analysis, single-cell and bulk RNA sequencing experiments identified a list of E2F target genes as downstream targets of YAP1 activation in chief cells during paligenosis. We conducted phosphoproteomic analyses using HDT-treated C57BL/6J mice and Ddit4 −/− mice and mapped the E2F target gene list identified by transcriptomics onto our proteomic dataset. Importantly, we identified Nme1, a well-known tumor suppressor gene that activates and stabilizes p53. We observed that NME1 levels are downregulated during stage 1 of paligenosis and return to basal levels by stage 3 in C57BL/6J mice, while in Ddit4 −/− mice, NME1 is downregulated in stage 1 but fails to recover in stage 3. Finally, we validated our multi-omic observations through western blotting and IHC. Our findings uncover a potentially novel YAP1-DDIT4-NME1 axis that suppresses p53 activity in paligenosis stage 2, which helps release p53 suppression of mTORC1 activity, together with the already described IFRD1-p53 regulation of the stage 2 to 3 transition. Elucidation of these and other molecular mechanisms that govern paligenosis will ultimately facilitate the development of novel therapies that can target tumorigenesis. JCM is supported by R01CA239645, R01DK105129, R01DK134531, R01CA246208 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.