Signals and mechanical forces controlling radial gut morphogenesis

项目摘要/摘要 中肠以一系列同心的、中胚层来源的平滑肌层为特征。 和粘膜，围绕着一个内层的内胚层来源的上皮。在成熟的肠道中，这种上皮形成 指状突起伸入管腔，称为绒毛。在发育中的雏鸡中，会产生肠道绒毛 以一种循序渐进的方式，通过一系列的上皮屈曲事件。屈曲力通过以下方式产生 当扩张受到邻近分化的限制时，上皮的受限生长。 平滑的肌肉。随着时间的推移，上皮细胞所经历的物理约束随着时间的不同而变化 平滑肌是按顺序建立的。这些平滑肌层的位置已经确定 通过Shh和BMP梯度的活性，分别对 平滑肌分化。当它们形成时，每一肌肉层中纤维的方向取决于 在蛋鸡经历分化时肠道的机械环境。尽管这位将军 关于中肠结构是如何建立的，关于组织水平的信息很匮乏 其他肠段的结构。前肠和后肠都来自同一个线性原语 肠管与中肠一样，并具有相同的一般同心组织。然而，有重要的 不同肠段中平滑肌分化的厚度和时间的差异，以及 三个节段的上皮衬里有很大的不同。在目标1中，负责不同的 前肠和后肠肌层的特征将被阐明。已知的信令系统 负责确定中肠平滑肌的位置和厚度将在 前肠和后肠节段定性(通过原位杂交)和定量(通过qPCR) 确定它们与中肠的表达有何不同。这些信号将通过通电来操纵 并通过在外植体培养中加入激动剂和拮抗剂以及利用组织重组来实现 从功能上测试他们的角色。目标2中的实验将确定这些差异在多大程度上 肌肉的结构和动力学是前后部不同的上皮形态的原因。 有胆量。药物将被用来阻止平滑肌分化，以测试其必要性。形态测量学和 生物物理参数将被测量并输入计算模型，以测试 在此基础上，可以完全解释上皮的形态。最后，在目标3中，我们将评估转录如何 HOX和ParaHox簇的因子，已知指定肠道内的区域同一性，改变了分子 以及区分前肠、中肠和后肠的物理参数，从而将区域图案连接到 肠道的形态发生。为此，涉及区域认同的转录因子将被错误表达 利用逆转录病毒载体，将检测生化和机械参数的变化。

PROJECT SUMMARY/ABSTRACT The midgut is characterized by a series of concentric, mesodermally-derived layers of smooth muscle and mucosa, surrounding an inner, endodermally-derived epithelium. In the mature gut, this epithelium forms finger-like projections extending into the lumen, called villi. In the developing chick, intestinal villi are generated in a step-wise manner, through a series of epithelial buckling events. Buckling forces are generated through the confined growth of the epithelium at a time when expansion is restricted by the adjacent differentiating smooth muscle. The physical constraint experienced by the epithelium changes over time as different layers of smooth muscle are established sequentially. The location of these smooth muscle layers is established through the activity of gradients of Shh and Bmp, which, respectively, have positive and negative effects on smooth muscle differentiation. As they form, the orientation of the fibers in each muscle layer depends upon the mechanical environment of the gut at the time the layer undergoes differentiation. In spite of this general outline of how the midgut architecture is established, there is a dearth of information regarding the tissue-level construction of the other gut segments. Both the foregut and the hindgut arise from the same linear primative gut tube as the midgut, and have the same general concentric organization. However, there are significant differences in the thickness and timing of smooth muscle differentiation in the different gut segments, and the epithelial lining differs dramatically in the three segments. In Aim 1, the mechanisms responsible for the distinct characteristics of the muscle layers in the fore- and hindgut will be elucidated. The signaling systems known to be responsible for defining the location and thickness of the smooth muscle in the midgut will be examined in the fore- and hindgut segments qualitatively (by in situ hybridization) as well as quantitatively (by qPCR) to determine how they differ in expression from the midgut. These signals will be manipulated by electoration in vivo and through culturing with agonists and antagonists in explant culture and utilizing tissue recombination to test their roles functionally. Experiments in Aim 2 will determine the extent to which these differences in smooth muscle architecture and dynamics are responsible for the distinct epithelial morphology of the fore-and hind guts. Drugs will be employed to block smooth muscle differentiation to test their necessity. Morphometric and biophysical parameters will be measured and entered into computational models to test the degree to which epithelial morphology can be entirely explained on this basis. Finally, in Aim 3 we will assess how transcription factors of the Hox and paraHox clusters, known to specify regional identity within the gut, alter the molecular and physical parameters that differentiate the fore-, mid- and hindgut, thereby connecting regional patterning to morphogenesis of the gut. To that end, transcription fctors involved in regional identity will be misexpressed ustilizing retroviral vectors, and changes in biochemical and mechanical parameters will be examined.