The Role of AML1 in Osteoclastogenesis and Osteoclast Gene Expression

这项研究的总体目标是了解转录因子指定的机制 破骨细胞谱系定位和分化。这一建议具有重要意义，因为它澄清了 破骨细胞谱系定位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了洞察力 靶向缺失c-fos、PU.1、NF-κB和NFATc1转录因子基因的机制 决定破骨细胞(OC)谱系定位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均可诱导前体细胞分化为破骨细胞。我们的 初步研究表明，AML1结合位点是组织蛋白K关键顺式调节元件(CCRE)， 证实AML1是其反式调节因子，并证明AML1高度受RANKL和 巨噬细胞集落刺激因子。RANKL和M-CSF阻断对小鼠骨髓培养中AML1基因表达的影响 破骨细胞分化，但不抑制巨噬细胞分化。然而，AML1-/-肝细胞未能 同时发育单核/巨噬细胞和破骨细胞。我们的结果表明，AML1可能控制 破骨细胞谱系定位及通过上调调控破骨细胞基因表达和分化 PU.1和NFATc1。根据我们的初步研究，我们假设AML1是一个关键的调节因子 这在转录调控水平上规定了破骨细胞的谱系定位和分化。我们 将通过两个具体目标来检验这一假设。我们将确定AML1在破骨细胞中的功能作用 在目标1中使用RNAi敲除和过度表达的谱系承诺和分化。我们将 通过骨组织特异性靶向研究AML1在成年小鼠破骨细胞分化中的作用 通过Cre/loxP技术使用条件基因敲除方法中断AML，并表征 AML1条件性基因敲除小鼠的表型和发病机制。最终，这一知识将 有助于确定AML1在破骨细胞谱系定位和分化中的作用。因此，它将 提高我们对溶骨性疾病的认识，并帮助设计新的治疗方法 使用药物或体细胞基因治疗的疾病，如骨质疏松症、关节炎、牙周病和骨转移。

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.