ESTROGEN RECEPTOR SIGNALING PATHWAYS IN BONE

骨骼是雌激素（E）作用的主要靶点之一，因为E调节骨生长和重塑。 虽然已知E水平降低是骨质疏松症的主要原因之一，但特定的分子水平降低是导致骨质疏松症的主要原因之一。 E调节骨代谢的途径尚未完全表征或理解。这个项目 使用新的小鼠和细胞模型的组合来定义，在细胞和分子水平上， E调节骨转换和骨量的信号通路，重点关注两种方式， 雌激素受体-α（ER α）的功能：经典的作用模式，其中ER α直接与 雌激素反应元件（ERes）对DMA的影响，以及ERa间接发挥作用的非经典模式 通过与其他转录因子的蛋白质-蛋白质相互作用。初步数据显示， 含有消除经典ER α信号传导的ER α突变（NERKI）的人表现出骨质减少和受损， 雄性动物的皮质骨和松质骨均有骨形成，但雌性动物仅在皮质骨中有骨形成。我们 假设由于雌性小鼠中E水平的增加，ER β起到减轻 松质骨中的NERKI受体。在目标1中，我们通过评估ERB的损失是否 导致雌性NERKI小鼠的骨骼缺陷更大，但对雄性NERKI小鼠无影响。我们会检查野生型的骨头， NERKI//ERB+/+和NERKI//ERB-/-小鼠，使用骨密度测定法和组织形态测定法。Aim 2对此进行了测试 通过评估这些小鼠的骨髓基质细胞的能力， 沿着成骨细胞谱系定型和分化。使用定量聚合酶链反应分析， 我们将检验NERKI受体的表达导致对Wnt的应答受损的假设， BMP，而ERP调节这些作用。目的3检查了细胞膜上经典ER α信号转导的丢失， 使用染色质免疫沉淀将NERKI受体募集至非经典DNA结合位点 测定。最后，Aim 4使用一种新的转基因方法来检查选择性的骨骼影响。 仅在成骨细胞中用NERKI受体替代内源性ER α。总的来说，这些研究 将提供一个更详细的了解ER信号通路在骨。

The skeleton is one of the main targets of estrogen (E) action, as E regulates bone growth and remodeling. Although decreased E levels are known to be one of the main causes of osteoporosis, the specific molecular pathways by which E regulates bone metabolism are not fully characterized or understood. This Project uses a combination of novel mouse and cell models to define, at the cellular and molecular level, the signaling pathways by which E regulates bone turnover and bone mass, focusing on two modalities by which the estrogen receptor-alpha (ERa) functions: the classical mode of action, where ERa directly interacts with estrogen response elements (EREs) on DMA, and the non-classical mode, where ERa indirectly functions through protein-protein interactions with other transcription factors. Preliminary data demonstrates that mice containing an ERa mutation that eliminates classical ERa signaling (NERKI) exhibit osteopenia and impaired bone formation in both cortical and trabecular bone in males, but only in cortical bone in females. We hypothesize that due to increased E levels in female mice, ER(3 functions to mitigate the negative effects of the NERKI receptor in trabecular bone. In Aim 1, we directly test this by assessing whether loss of ERB leads to greater skeletal deficits in female, but not male NERKI mice. We will examine bones from wild type, NERKI//ERB+/+, and NERKI//ERB-/- mice using bone densitometry and histomorphometry. Aim 2 tests this hypothesis at the cellular level by assessing the ability of bone marrow stromal cells from these mice to commit and differentiate along the osteoblast lineage. Using quantitative polymerase chain reaction assays, we will test the hypotheses that expression of the NERKI receptor leads to impaired responses to Wnts and BMPs, and that ERP modulates these effects. Aim 3 examines loss of classical ERa signaling on the recruitment of the NERKI receptor to non-classical DNA binding sites using chromatin immunoprecipitation assays. Finally, Aim 4 uses a novel transgenic approach to examine the skeletal consequences of selective replacement of the endogenous ERa with the NERKI receptor only in osteoblasts. Collectively, these studies will provide a more detailed understanding of ER signaling pathways in bone.