The Role of AML1 in Osteoclastogenesis and Osteoclast Gene Expression

本研究的总体目标是了解转录因子指定的机制， 破骨细胞谱系定型和分化。这一建议意义重大，因为阐明了 破骨细胞谱系定型和分化有可能定义新的骨治疗靶点 涉及破骨细胞生成和激活的疾病。尽管最近从这些影响中获得的见解 靶向删除c-fos、PU.1、NF-κB和NFATc 1转录因子基因， 决定破骨细胞（OC）谱系定型和分化的潜在转录因子仍然存在， 不清楚需要进一步的研究来阐明为什么M-CSF单独诱导前体细胞分化为 巨噬细胞，而M-CSF和RANKL均诱导前体细胞分化为破骨细胞。我们 初步研究揭示了AML 1结合位点作为组织蛋白酶K关键顺式调节元件（CCRE）， 证实了AML 1是其反式调节因子，并证明了AML 1受RANKL高度诱导， M-CSF在一起RANKL和M-CSF阻断小鼠骨髓培养物中AML 1的敲低 破骨细胞分化，但不抑制巨噬细胞分化。然而，AML 1-/-肝细胞未能 发展单核细胞/巨噬细胞和破骨细胞。我们的研究结果表明，AML 1可能控制 破骨细胞谱系定型并通过上调破骨细胞基因表达和分化来调节破骨细胞的分化 PU.1和NFATc 1。基于我们的初步研究，我们假设AML 1是一个关键的调节因子， 其在转录调控水平指定破骨细胞谱系定型和分化。我们 将通过两个具体目标来检验这一假设。我们将明确AML 1在破骨细胞中的功能作用， 在Aim 1中使用RNAi敲低和过表达的谱系定型和分化。我们将 通过骨组织特异性靶向的方法研究AML 1在成年小鼠破骨细胞分化中的作用 通过Cre/loxP技术使用条件性敲除方法破坏AML，并表征 表型和病理机制的AML 1条件敲除小鼠。最终，这些知识将 有助于确定AML 1在破骨细胞谱系定型和分化中的作用。因此，它将 提高我们对溶骨性疾病的理解，并帮助设计新的治疗方法， 例如骨质疏松症、关节炎、牙周病和骨转移的疾病，使用药物或体细胞基因疗法。

The overall goal of this study is to understand the mechanism underlying transcription factors specifying osteoclast lineage commitment and differentiation. This proposal is highly significant since elucidating osteoclast lineage commitment and differentiation has potential to define new therapeutic targets for bone disorders that involve osteoclast generation and activation. Despite the recent insights gained from the effects of targeted deletion of the c-fos, PU.1, NF-κB, and NFATc1 transcription factor genes, the mechanism underlying transcription factors specifying osteoclast (OC) lineage commitment and differentiation remains unclear. Further study is needed to clarify why M-CSF alone induces precursors to differentiate into macrophages while both M-CSF and RANKL induce precursors to differentiate into osteoclasts. Our Preliminary Studies revealed an AML1 binding site as a cathepsin K critical cis-regulatory element (CCRE), confirmed AML1 as its trans-regulatory factor, and demonstrated that AML1 is highly induced by RANKL and M-CSF together. AML1 knockdown in mouse bone marrow culture induced by RANKL and M-CSF blocked osteoclast differentiation, but did not inhibit macrophage differentiation. However, AML1-/- liver cells failed to develop both monocytes/macrophages and osteoclasts. Our results showed that that AML1 may control osteoclast cell lineage commitment and regulate osteoclast gene expression and differentiation through upregulating PU.1 and NFATc1. Based on our Preliminary study, we hypothesize that AML1 is a key regulator that specifies osteoclast cell lineage commitment and differentiation at the transcriptional regulation level. We will test this hypothesis through two specific aims. We will define the functional role of AML1 in osteoclast cell lineage commitment and differentiation using RNAi knockdown and overexpression in Aim 1. We will investigate the role of AML1 in osteoclast differentiation in adult mice through bone tissue-specific targeted disruption of AML using a conditional knockout approach by Cre/loxP technology and characterize the phenotypes and pathomechanism of the AML1 conditional knockout mice. Ultimately, this knowledge will help to establish the roles of AML1 in osteoclast cell lineage commitment and differentiation. Thus, it will improve our understanding of osteolytic diseases and help to design novel approaches for the treatment of diseases such as osteoporosis, arthritis, periodontal disease, and bone metastases using drug or somatic gene therapy.