Cell: Cell Interactions During Late Intestinal Development

描述（由申请方提供）：小肠上皮组织为瓶状腺体（隐窝），含有肠干细胞和被分化细胞覆盖的指状突起（绒毛）。细胞分裂、分化和迁移的恒定过程是沿着沿着极化的隐窝到绒毛轴建立的。该垂直轴的建立和维持需要上皮和下层间充质之间的细胞：细胞串扰，并且对于肠的适当稳态至关重要。对一种新建立的刺猬（Hh）信号被阻断的小鼠模型（Hhip转基因小鼠）的分析表明，隐窝/绒毛轴的建立需要这种信号通路。Hh信号从上皮发出并被间充质接收。Shh和Ihh参与了这一信号;这两种信号蛋白既有重叠的作用，又有独立的作用。组合Hh信号的丧失允许在绒毛尖端上形成异位的前隐窝结构，从而破坏隐窝/绒毛轴的正常组织。Hhip小鼠的上皮表型反映了上皮细胞和上皮下肌成纤维细胞的扩增群体之间的细胞：细胞串扰的改变。该提案测试了以下假设：来自上皮的组合Ihh和Shh信号被上皮下肌成纤维细胞接收，并间接限制和组织Wnt响应性上皮前隐窝区室。在目的1中，将在野生型、Shh -/-、Ihh -/-和Hip小鼠中比较在晚期肠发育期间伴随隐窝/绒毛轴极化的分子和形态学事件的序列。在目标2中，将鉴定间充质隔室中Hh信号传导的靶标。将寻求Shh和Ihh的单独和共同靶标;将测试Hh在不同浓度下诱导不同基因的可能性。最后，目标3探索了Hh蛋白如何组织隐窝/绒毛轴（即，通过形态发生梯度的极化或通过前隐窝区域的锚定），并测试特定候选基因在该轴模式化中的作用。这项工作将为细胞提供新的见解：细胞信号通路对肠道发育至关重要。

DESCRIPTION (provided by applicant): The small intestinal epithelium is organized into flask-like glands (crypts) that contain intestinal stem cells and finger-like projections (villi) covered by differentiated cells. A constant process of cell division, differentiation and migration is established along a polarized crypt to villus axis. Establishment and maintenance of this vertical axis requires cell:cell crosstalk between the epithelium and the underlying mesenchyme and is critical to proper homeostasis of the intestine. Analysis of a newly established mouse model in which hedgehog (Hh) signals are blocked (Hhip transgenic mice) reveals that establishment of the crypt/villus axis requires this signaling pathway. Hh signals emanate from the epithelium and are received by the mesenchyme. Shh and Ihh participate in this signal; these two signaling proteins have both overlapping and separate roles. Loss of the combined Hh signal permits the formation of ectopic pre-crypt structures on villus tips, thus disrupting the normal organization of the crypt/villus axis. The epithelial phenotype of Hhip mice reflects alterations in cell:cell crosstalk between the epithelial cells and an expanded population of subepithelial myofibroblasts. The proposal tests the following Hypothesis: A combined Ihh and Shh signal from the epithelium is received by subepithelial myofibroblasts and acts indirectly to limit and organize the Wnt responsive epithelial pre-crypt compartment. In Aim 1, the sequence of molecular and morphological events that accompany crypt/villus axis polarization during late intestinal development will be compared in wild type, Shh -/-, Ihh -/- and Hhip mice. In Aim 2, the targets of Hh signaling in the mesenchymal compartment will be identified. Separate and common targets of Shh and Ihh will be sought; the possibility that Hh induces different genes at different concentrations will be tested. Finally, Aim 3 explores how Hh proteins function to organize the crypt/villus axis (i.e., by polarization via a morphogen gradient or by anchoring of the pre-crypt region) and tests specific candidate genes for their role in patterning this axis. The work will provide new insights into cell:cell signaling pathways crucial for intestinal development.