Discrete regulation of β-catenin-mediated transcription governs identity of intestinal epithelial stem cells [RNA-Seq]. Discrete regulation of β-catenin-mediated transcription governs identity of intestinal epithelial stem cells [RNA-Seq]

The homeostasis of the gut epithelium relies upon continuous renewal and proliferation of crypt-resident intestinal epithelial stem cells (IESCs). Wnt/β-catenin signaling is required for IESC maintenance, however, it remains unclear how this pathway selectively governs the identity and proliferative decisions of IESCs. Here, we demonstrate that C-terminally-recruited transcriptional co-factors of β-catenin act as all-or-nothing regulators of Wnt-target gene expression. Blocking their interactions with β-catenin rapidly induces loss of IESCs and intestinal homeostasis. Conversely, N-terminally recruited co-factors fine-tune β-catenin’s transcriptional output to ensure proper self-renewal and proliferative behaviour of IESCs. Impairment of N-terminal interactions triggers transient hyperproliferation of IESCs, resulting in exhaustion of the self-renewing stem cell pool. IESC mis-differentiation, accompanied by intrinsic and extrinsic stress signalling results in a process resembling aberrant "villisation" of intestinal crypts. Our data suggest that IESC-specific Wnt/β-catenin output requires discrete regulation of transcription by transcriptional co-factors. Overall design: RNA sequencing of bulk extracts of murine small intestinal epithelium of betacatenin-mutant mice (4xcontrol, 3xD164A, 2xDeltaC, 2xdm, 2xKO)

肠道上皮稳态依赖于隐窝驻留肠道上皮干细胞（intestinal epithelial stem cells, IESCs）的持续更新与增殖。Wnt/β-连环蛋白（Wnt/β-catenin）信号通路是维持IESC所必需的，但目前仍不清楚该通路如何选择性调控IESC的细胞身份与增殖决策。本研究证实，β-连环蛋白的C端招募的转录辅因子可作为Wnt靶基因表达的“全有或全无”调控因子。阻断其与β-连环蛋白的相互作用，会快速诱导IESC丢失与肠道稳态失衡。反之，N端招募的辅因子可精细调控β-连环蛋白的转录输出，以保障IESC的正常自我更新与增殖行为。N端相互作用的受损会触发IESC的短暂过度增殖，最终导致自我更新干细胞池耗竭。IESC的异常分化伴随内在与外在应激信号通路激活，会引发类似肠道隐窝异常“绒毛化（villisation）”的过程。本研究数据表明，IESC特异性的Wnt/β-连环蛋白转录输出需要通过转录辅因子对转录过程进行差异化调控。整体实验设计：对β-连环蛋白突变小鼠的小肠上皮批量提取物进行RNA测序（RNA sequencing），其中对照组4例、D164A突变组3例、DeltaC突变组2例、dm突变组2例、KO组2例。