Dab1 expression and activity in mammary epithelial cells.

描述(申请人提供)：Reelin信号通路作为发育中的中枢神经系统中细胞定位和迁移的关键调节因子，已经研究了50多年。我的实验室最近发现了Reelin信号在调节乳腺形态发生中的一个新角色。利用免疫组织化学方法和报告基因的表达，我们发现在发育和成熟的乳腺中表达了reelin信号通路的组成部分，并且在体内，reelin信号的改变导致导管的不正确分支和扰乱上皮组织，导致乳腺导管网络的异常发育。我们还表明，分离的乳腺上皮细胞排列在导管管腔内，在Reelin蛋白存在的情况下减缓它们的迁移。这些观察结果导致了一种假设，即卷轴信号可能是乳腺细胞迁移的关键调节因素。这项建议将解决Dab1，一种细胞内适配器蛋白，它是响应reelin信号而被激活的，如何在调节乳腺上皮细胞的行为中发挥作用。已经在胚胎脑和视网膜中发现了几种Dab1亚型；这些亚型可能允许对reelin存在的不同反应和对reelin信号的细微反应。我的实验室已经证明了几种不同的Dab1亚型在乳腺中的表达，这一提议将确定这些亚型的生物学功能。首先，我们将确定在何时何地表达不同的异构体，期望在增殖和迁移的乳腺上皮细胞中表达的异构体将不同于在静止细胞中表达的异构体。其次，我们将确定在体外和体内，改变异构体表达是否会改变乳腺上皮细胞的行为。第三，我们将确定乳腺上皮细胞中不同的Dab1亚型激活了reelin信号通路的哪些元件。在神经细胞中，Reelin信号有几种可供选择的结果，我们预计，异构体的表达可能决定了乳腺上皮细胞中激活了哪些通路元件。总之，这些实验将证明Dab1亚型的差异表达对于调节乳腺中的细胞行为是重要的。了解调控乳腺上皮细胞迁移的机制可能最终导致抑制乳腺癌细胞转移的治疗方法。

DESCRIPTION (provided by applicant): The reelin signaling pathway has been studied for over 50 years as a critical regulator of cell positioning and migration in the developing central nervous system. My laboratory has recently identified a novel role for reelin signaling in regulating mammary gland morphogenesis. Using immunohistochemical approaches and reporter gene expression, we have shown that components of the reelin signaling pathway are expressed in the developing and mature mammary gland and that alterations in reelin signaling cause improper ductal branching and disrupt epithelial organization in vivo, resulting in abnormal development of the mammary ductal network. We have also shown that isolated mammary epithelial cells, which line the ductal lumen, slow their migration in the presence of reelin protein. These observations lead to the hypothesis that reelin signaling may be a critical regulator of cell migration in the mammary gland. This proposal will address how Dab1, an intracellular adaptor protein that is activated in response to reelin signaling, functions in regulating the behavior of mammary epithelial cells. Several isoforms of Dab1 have been identified in embryonic brain and retina; these isoforms may allow a differential response to the presence of reelin and a nuanced response to reelin signaling. My laboratory has demonstrated the expression of several distinct Dab1 isoforms in the mammary gland and this proposal will determine the biological functions of these isoforms. First, we will determine when and where the different isoforms are expressed, with the expectation that isoforms expressed in proliferating and migrating mammary epithelial cells will be different from isoforms expressed in quiescent cells. Second, we will determine if changing isoform expression alters the behavior of mammary epithelial cells both in vitro and in vivo. Third, we will determine which elements of the reelin signaling pathway are activated by the different Dab1 isoforms in mammary epithelial cells. There are several alternative outcomes to reelin signaling in neuronal cells and we expect that isoform expression may dictate which elements of the pathways are activated in mammary epithelial cells. Together, these experiments will demonstrate that differential expression of Dab1 isoforms is important for the regulation of cellular behaviors in the mammary gland. Understanding the mechanisms that regulate mammary epithelial cell migration may ultimately lead to therapeutic approaches to inhibit the metastatic migration of breast cancer cells.