APC and Retinoids in Zebrafish Enterocyte Development

我们的长远目标是促进制定新的预防和治疗措施 通过了解APC突变后最早的细胞扰动来形成结肠癌。在……里面 在之前的融资阶段，我们揭示了一种创新的模式，在这种模式中，APC促进了肠细胞 通过控制维甲酸的生物合成进行分化。这些发现现在证明了 APC的功能并不局限于它在调节规范的WNT信号方面的既定作用。 从机制上讲，我们发现转录共抑制因子C末端结合蛋白(CtBP)是一种 抑制视黄醇脱氢酶和肠道细胞分化的新型APC调节蛋白 与调节失调的Lef-1协同工作。FAP患者的早期腺瘤显示水平升高 CtBP和LEF1与邻近未受累组织的比较。然而，令人惊讶的是，这些相同的 切片显示很少有核β-连环蛋白的证据表明维甲酸和细胞的丢失 分化先于β-连环蛋白的核积累。我们进一步证明了激活 KRAS促进了核β-连环蛋白的积聚，促进了随后的肠道细胞增殖。我们 还描述并揭示了APC和一种新的DNA去甲基酶之间的意外联系 系统。这种DNA去甲基酶在失去APC和维甲酸后上调，并维持 肠道细胞处于类祖细胞状态。这种分化失败先于K-RAS诱导的增殖 通过β-连环蛋白。目前还不清楚激活KRAS的信号在哪里，因此，β-连锁素 起源于APC损失的背景下。有趣的是，成年斑马鱼缺乏维甲酸 表现出分化缺陷和深刻的增殖反应，与 炎性基质细胞的激活。我们的初步发现表明，成年斑马鱼 缺乏免疫细胞的基因工程显示出肠道分化缺陷，但没有增殖反应 当缺乏维甲酸的时候。我们现在将扩大我们的研究范围，以检查维甲酸 在上皮细胞和肠道间质细胞中都发挥作用，以及它们之间的相互作用 结肠腺瘤的发生和发展有两种细胞群。我们假设 APC控制着维甲酸的生产。中国维甲酸生产的控制 肠上皮细胞通过重塑表观遗传学调节细胞分化潜能 风景。同时，维甲酸作用于抑制肠道炎症反应 需要刺激上皮细胞增殖。这个项目将扩大我们对APC如何 维甲酸有助于肠道发育和分化。这种理解可能会 支持一种可测试的临床假说，目的是在药物上重新激活维甲酸信号 预防和治疗人类结肠癌。

Our long-term goal is to facilitate the development of new prevention and therapeutic measures for colon cancer formation by understanding the earliest cellular perturbations that follow APC mutation. In the previous funding periods, we revealed an innovative model wherein APC promotes enterocyte differentiation by controlling retinoic acid biosynthesis. These findings now demonstrate that the functions of APC are not limited to its well-established role in regulating canonical WNT signaling. Mechanistically, we identified the transcriptional co-repressor, C-terminal binding protein (CtBP), as a novel, APC-regulated protein that suppresses retinol dehydrogenases and intestinal cell differentiation in concert with dysregulated LEF-1. Early adenomas taken from FAP patients showed elevated levels of CtBP and LEF1 in comparison to adjacent, uninvolved tissues. Surprisingly, however, these same sections showed little evidence of nuclear β-catenin indicating that loss of retinoic acid and cell differentiation precedes nuclear accumulation of β-catenin. We further demonstrated that activation of KRAS promoted the accumulation of nuclear β-catenin and subsequent intestinal cell proliferation. We also described and uncovered an unexpected connection between APC and a novel DNA demethylase system. This DNA demethylase is upregulated upon loss of APC and retinoic acid and maintains intestinal cells in progenitor-like state. This failed differentiation precedes K-RAS induced proliferation via β-catenin. It is currently unclear where signals for activating KRAS, and therefore, β-catenin originate in the context of APC loss. Interestingly, adult zebrafish made deficient in retinoic acid demonstrate both differentiation defects and a profound proliferation response that is coincident with activation of inflammatory stromal cells. Our preliminary findings indicate that adult zebrafish engineered to lack immune cells show intestinal differentiation defects, but no proliferative response when made deficient in retinoic acid. We will now expand our studies to examine whether retinoic acid plays roles in both epithelial cells and in intestinal stromal cells and whether interactions between these two cell populations account for both initiation and progression of colon adenomas. We hypothesize that APC controls the production of retinoic acid. Control of retinoic acid production in intestinal epithelial cells regulates cell potential for differentiation by remodeling the epigenetic landscape. In parallel, retinoic acid acts to suppress intestinal inflammatory responses that are need to stimulate epithelial cell proliferation. This project will expand our understanding of how APC and retinoic acid contribute to intestinal development and differentiation. This understanding could support a testable clinical hypothesis aimed at pharmacological re-activation of retinoid signaling in preventing and treating human colon cancers.