Abstract 918: Cdc42 is crucial for intestinal stem cells survival by regulating Wnt and YAP signaling

Abstract

Abstract Strictly defined architecture of intestinal epithelial cells and the gradient of signaling cues along the villus-crypt axis ensure the maintenance of adult intestinal stem cells, as well as proper regeneration and differentiation of all intestinal epithelial cell types. The Rho family small GTPase Cdc42 controls the polarized division of intestinal stem cells, and affects subsequent fate-determination of the progenitor cells. As we previously described in Cdc42 Villin-Cre knockout mice, loss of Paneth cells from crypt bottom and emergence of Goblet cell-like intermediate cells at the villus indicate possible compromise of the canonical Wnt signaling during Paneth cell differentiation. Here we further characterized the underlying molecular mechanism of Cdc42 regulating intestinal stem cell survival, proliferation, and differentiation. IHC of the intestinal tissue in Cdc42 Villin-Cre knockout mice suggests greatly reduced Olfm4 level in the stem cells, which are abnormally positioned in the crypts, along with a reduction of both transcription co-factors beta-Catenin and YAP. However, the Notch signaling, which is required for stem cells and the differentiation of absorptive linage, seems intact. The autonomous regulation of Cdc42 on Yap signaling is probably through its specific role in stabilizing cell-cell junction and actin filaments in the epithelium, both of which are known regulatory inputs of the Hippo-YAP pathway. Both Wnt/beta-Catenin and Yap signaling are required for the initiation and progression of colorectal cancer, and the regeneration of stem cells post radiation. Given that Cdc42 is overexpressed in multiple types of cancers, especially colorectal cancer, our finding that Cdc42 regulates both Wnt and YAP pathways in the homeostasis of adult intestinal tissue sheds new light on the molecular mechanism of its pathological involvement, and potential therapeutic target. Citation Format: Xiao Zhang, Nan Gao. Cdc42 is crucial for intestinal stem cells survival by regulating Wnt and YAP signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 918. doi:10.1158/1538-7445.AM2017-918