Dab1 expression and activity in mammary epithelial cells.

描述（由申请人提供）：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，reelin信号通路已经被研究了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新作用。利用免疫组织化学方法和报告基因表达，我们已经证明了reelin信号通路的组成部分在发育和成熟的乳腺中表达，并且reelin信号通路的改变导致体内导管分支不正常并破坏上皮组织，导致乳腺导管网络发育异常。我们还表明，在存在reelin蛋白的情况下，排列在导管腔内的分离乳腺上皮细胞的迁移速度会减慢。这些观察结果导致了一个假设，即reelin信号传导可能是乳腺细胞迁移的关键调节因子。本研究将探讨Dab1（一种响应reelin信号而被激活的细胞内衔接蛋白）在调节乳腺上皮细胞行为中的作用。在胚胎脑和视网膜中已经发现了几种Dab1亚型；这些同工异构体可能允许对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，我们将确定不同的异构体在何时何地表达，期望在增殖和迁移的乳腺上皮细胞中表达的异构体与在静止细胞中表达的异构体不同。其次，我们将确定改变异构体表达是否会改变体外和体内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。神经细胞中的reelin信号有几种不同的结果，我们期望同种异构体的表达可能决定了乳腺上皮细胞中哪些信号通路被激活。总之，这些实验将证明Dab1亚型的差异表达对乳腺细胞行为的调节是重要的。了解调节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性迁移的治疗方法。

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.