Regulation and molecular function of the T-box transcription factors Tbx2 and Tbx3 in the development of the murine lung

脊椎动物器官的发育依赖于相邻组织室中增殖速率和分化模式的精确时空协调。在胚胎肺的分支形态发生过程中，上皮内胚层分支尖端分泌的许多信号维持下层间质处于未分化的增殖状态，这反过来又需要维持远端肺芽上皮的前体细胞，并允许继续生长。尽管在包括肺在内的许多器官的发育中已经发现了维持前体组织增殖的单个信号，但尚不清楚这些信号是如何整合并转化为细胞周期控制的。我们最近的研究表明，T-box转录抑制因子Tbx2通过直接抑制细胞周期抑制基因Cdkn1a和Cdkn1b来维持肺间质的增殖和抑制分化。我们进一步的初步工作表明，Tbx2和密切相关的Tbx3整合了各种上皮信号，抑制间质中多种抗增殖基因的活性。因此，我们希望在发展中确定Tbx2和Tbx3的上游调控模块和下游效应物。Tbx2和tbx3在肺间质表达的控制分析。我们希望确定在时间和空间上诱导和/或维持Tbx2/Tbx3表达的信号通路（Shh、Wnt、Bmp和Tgfß）的单独和联合活性，并表征Tbx2/Tbx3功能对肺中这些信号活性的贡献。Tbx2/Tbx3在肺间质中的分子功能分析。我们希望进一步表征缺乏Tbx2、Tbx3和Tbx2/Tbx3的胚胎肺和过表达Tbx2的成人肺的分子和细胞变化，分析Wnt、Bmp和干扰素信号/干扰素调节因子作为Tbx2/Tbx的下游效应因子的作用，并鉴定Tbx2和Tbx3在该组织中的直接靶点。我希望通过这些实验对维持发育中的肺分支形态发生的调控网络以及肺间质中Tbx2/Tbx3调节的增殖和分化途径的复杂性有新的见解。这一发现也可能有助于更好地理解Tbx2和Tbx3上调在许多癌症中的意义。

Vertebrate organ development relies on the precise spatiotemporal orchestration of proliferation rates and differentiation patterns in adjacent tissue compartments. During branching morphogenesis of the embryonic lung, a number of signals secreted from the epithelial endodermal branch tips maintain the underlying mesenchyme in an undifferentiated proliferative state which in turn is required to maintain precursor cells in the distal lung bud epithelium, and allow continued outgrowth. Although individual signals that maintain proliferation of precursor tissues have been identified in the development of many organs, including the lung, it has remained unclear how these signals are integrated and translated into cell-cycle control. Our recent work has shown that the T-box transcriptional repressor Tbx2 maintains proliferation and inhibits differentiation of the pulmonary mesenchyme by directly repressing the cell-cycle inhibitor genes Cdkn1a and Cdkn1b. Our additional preliminary work suggests that Tbx2 and the closely related Tbx3 integrate various epithelial signals to repress a diverse set of anti-proliferative gene activities in the mesenchyme. Therefore, we wish to define the upstream regulatory modules and the downstream effectors of Tbx2 and Tbx3 in the developing lunThe specific aims of this proposal are:1. Analysis of the control of Tbx2 andTbx3 expression in the lung mesenchyme.We wish to determine the individual and combined activities of signaling pathways (Shh, Wnt, Bmp and Tgfß) that induce and/or maintain expression of Tbx2/Tbx3 in time and space, and characterize the contribution of Tbx2/Tbx3 function to these signaling activities in the lung.2. Analysis of the molecular function of Tbx2/Tbx3 in the lung mesenchyme. We wish to further characterize the molecular and cellular changes in embryonic lungs lacking Tbx2, Tbx3 and Tbx2/Tbx3, and in adult lungs overexpressing Tbx2, analyze the role of Wnt, Bmp and interferon signaling/interferon regulatory factors as downstream effectors of Tbx2/Tbx, and identify and characterize direct targets of Tbx2 and Tbx3 in this tissue. I expect from these experiments new insight into the regulatory network that maintains branching morphogenesis in the developing lung and into the complexity of the proliferative and differentiation pathways regulated by Tbx2/Tbx3 in the pulmonary mesenchyme. This insight might also be useful to better understand the significance of upregulation of Tbx2 and Tbx3 in a number of cancers.