Cell: Cell Interactions During Late Intestinal Development

描述（由申请人提供）：小肠上皮组织成瓶状腺体（隐窝），其中含有肠干细胞和被分化细胞覆盖的指状突起（绒毛）。一个持续的细胞分裂、分化和迁移过程沿着一个极化隐窝到绒毛轴建立。这种垂直轴的建立和维持需要上皮细胞和下层间质之间的细胞串扰，这对肠道的正常稳态至关重要。对新建立的hedgehog （Hh）信号被阻断的小鼠模型（hip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，由间质接收。Shh和Ihh参与这个信号；这两种信号蛋白既有重叠又有独立的作用。Hh信号的缺失导致绒毛尖端形成异位隐窝前结构，从而破坏隐窝/绒毛轴的正常组织。hip小鼠的上皮表型反映了细胞的改变：上皮细胞和上皮下肌成纤维细胞之间的细胞串扰。该建议验证了以下假设：来自上皮的Ihh和Shh联合信号被上皮下肌成纤维细胞接收，并间接限制和组织Wnt应答的上皮隐窝前腔室。在Aim 1中，将比较野生型、Shh -/-、Ihh -/-和hip小鼠在肠道发育后期伴随隐窝/绒毛轴极化的分子和形态学事件序列。在Aim 2中，将确定间质室中Hh信号的靶标。将寻找Shh和Ihh的单独和共同目标；将测试Hh在不同浓度下诱导不同基因的可能性。最后，Aim 3探讨Hh蛋白如何组织隐窝/绒毛轴（即，通过形态梯度的极化或通过隐窝前区域的锚定），并测试特定的候选基因在该轴的模式中的作用。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.