SHP2 Regulation of the Plasticity of Bone Marrow Osterix+ Stroma

（请保持文字，不要PDF）本节必须不超过30行的文字。 最近有报道称，主成骨转录因子OSTERIX的启动子在围产期造血细胞中具有活性，并且GFP+血细胞在Tg（Osx-GFP：Cre）报告小鼠中以低频率循环。然而，目前还不知道造血细胞特异性OSTERIX表达的意义，以及OSTERIX消耗是否会影响造血。该提案中概述的工作建立在Osx-GFP标记一些BM和外周血细胞的新发现的基础上，这些GFP+血细胞的数量在发育和成熟过程中减少和消失。由于OSTERIX在造血系统中的表达和功能在很大程度上仍是未知的，这些发现共同刺激了OSTERIX在造血干细胞（HSC）中暂时表达的假设，并且它是造血干细胞存活和/或谱系定型和造血稳态所必需的。为了验证这一新的假设，我们提出了两个具体的目标。在目标1中，我们将通过使用FACS分析定量胚胎、出生后和成年Tg（Osx-GFP：Cre）小鼠中的GFP+血细胞来确定OSTERIX表达的动力学。在目标2中，我们将使用Tg（Mx 1-Cre;Osxfx/fx）在p（I）（C）诱导后确定HSC中OSTERIX耗竭对细胞存活和多系分化的影响。这项创新性研究将首次描述OSTERIX在造血系统中的调节作用，并提供有关OSTERIX在血液中调节异常影响的基础信息。成功完成所提出的工作将对我们理解Osterix的造血调节产生重大影响，并提高我们对Osterix在皮肤外组织中的认识。

(PLEASE KEEP IN WORD, DO NOT PDF) This section must be no longer than 30 lines of text. It has been recently reported that the promoter of the master osteogenic transcription factor, OSTERIX, is active perinatally in hematopoietic cells, and that GFP+ blood cells circulate at low frequency in Tg(Osx-GFP:Cre) reporter mice. However, nothing is currently known about the significance of the hematopoietic cell-specific OSTERIX expression, and whether OSTERIX depletion might impact hematopoiesis. The work outlined in this proposal builds on the novel findings that Osx-GFP marks some BM and peripheral blood cells, and the number of these GFP+ blood cells decreases and disappears during development and maturation. Since OSTERIX expression and function in the hematopoietic system remain largely unknown, these findings together stimulate the hypothesis that OSTERIX is temporarily expressed in hematopoietic stem cells (HSCs) and that it is required for their survival, and/or lineage commitment and hematopoietic homeostasis. To test this novel hypothesis, we propose two specific Aims. In Aim 1, we will determine the dynamics of OSTERIX expression by quantifying GFP+ blood cells in embryonic, postnatal, and adult Tg(Osx-GFP:Cre) mice using FACS analysis. In Aim 2, we will determine the impact of OSTERIX depletion in HSCs on cell survival and multilineage differentiation using Tg(Mx1-Cre;Osxfx/fx) upon p(I)(C) induction. This innovative study will result in the first-ever description of OSTERIX’s regulatory role in the hematopoietic system and provide foundational information on the effect of OSTERIX dysregulation in blood. Successful completion of the work proposed will have a significant impact on our understanding of the hematopoietic regulation by OSTERIX and advance our knowledge about OSTERIX in the extraskeletal tissues.