Morphogenesis of the fetal intestinal epithelium

摘要 成年人的肠道长度超过20英尺，功能性吸收表面积接近2000 平方英尺三个主要过程（发生在出生前）建立了有效的吸收表面 维持生命所需的：a）肠延长; B）绒毛的产生和c）顶端表面极化。的 这些属性背后的分子过程在临床上和治疗上是重要的，但在临床上和治疗上是不好的。 明白在上一个项目期的工作中建立了肠道生长模型，其特点是快速生长， 细胞增殖、低凋亡和细胞沿前/后（A/P）轴沿着方向分散。分析 Wnt 5a空肠（短肠模型）显示，在运动间隙期间，放射状丝状伪足的延伸存在缺陷。 核迁移、凋亡增加、pJNK活性降低、高尔基体定位改变和细丝蛋白减少 A.目的1由Wnt 5a-Ror 2-细丝蛋白A途径控制放射状丝状伪足延伸的假设驱动， 确保上皮细胞的存活;这对于适当的延长是重要的。将探索这条途径 使用遗传工具和肠外植培养。 在E14.5，上皮下间充质簇形成，导致覆盖的上皮细胞改变形状。 簇之间的上皮细胞激活Cd 44 v6;这些区域中的圆形有丝分裂细胞似乎驱动了一个细胞周期。 决定绒毛结构域的快速内陷过程。驱动目标2的假设是上皮细胞 内陷限定了第一绒毛的顶端表面;这个过程是由图案化的间充质细胞驱动的。 在机械力和专门的细胞分裂的帮助下。上皮内压的作用， 有丝分裂进程和定向细胞分裂的需要将被检查;阻碍内陷的基础 在Ezrin-/-小鼠中进行研究。 最后，根尖表面极化和成熟的细胞和分子方面的研究将在 早期人类内胚层使用一种新的体外模型系统。目标3的基本假设是： 由FLNA和CLMP突变引起的先天性短肠导致不适当的顶端极化。的 极化的分子序列将在分化的CDX 2细胞的培养物中建立， 将确定该序列上的短肠突变。 通过关注早期肠道发育生物学的细胞生物学基础，这些研究 揭示了建立用于产生顶端吸收表面的模板的关键过程。 数据的数学建模揭示了哪些参数在发育过程中最关键。

Abstract The adult human intestine is over 20 feet long and has a functional absorptive surface area of nearly 2,000 square feet. Three major processes (which take place prior to birth) establish the effective absorptive surface required to sustain life: a) intestinal lengthening; b) generation of villi and c) apical surface polarization. The molecular processes underlying these attributes are important clinically and therapeutically, but are poorly understood. Work in the last project period established a model of intestinal growth, characterized by rapid proliferation, low apoptosis and directional dispersion of cells along the anterior/posterior (A/P) axis. Analysis of Wnt5a null intestines (a short bowel model) revealed defects in extension of radial filopodia during interkinetic nuclear migration, increased apoptosis, reduced pJNK activity, altered Golgi positioning and reduced Filamin A. Aim 1 is driven by the hypothesis that a Wnt5a-Ror2-Filamin A pathway controls radial filopodial extension, insuring cell survival in the epithelium; this is important for proper lengthening. This pathway will be explored using genetic tools and intestinal explant cultures. At E14.5, subepithelial mesenchymal clusters form, causing overlying epithelial cells to change shape. Epithelial cells between clusters activate Cd44v6; rounded mitotic cells in these regions appear to drive a process of rapid invagination that determines the villus domains. The hypothesis driving Aim 2 is that Epithelial invagination defines the apical surfaces of the first villi; this process is driven by patterned mesenchymal clusters and aided by mechanical forces and specialized cell divisions. The role of intra-epithelial pressure and the need for mitotic progression and oriented cell division will be examined; the basis for impeded invagination in Ezrin-/- mice will be investigated. Finally, the cellular and molecular aspects of apical surface polarization and maturation will be studied in the early human endoderm using a new in vitro model system. The hypothesis underlying Aim 3 is: Human congenital short bowel caused by mutations in FLNA and CLMP result in improper apical polarization. The molecular sequence of polarization will be established in cultures of differentiating CDX2 cells and effects of short bowel mutations on that sequence will be determined. By focusing on the cell biology underlying the developmental biology of the early intestine, these studies are unveiling key processes that establish the template for generation of the apical absorptive surface. Mathematical modeling of the data is revealing which parameters are most critical over developmental time.