Bone Cell Growth Regulation by Runx2/Cbfa1

描述(申请人提供)：骨骼再生医学有望减轻与年龄相关的骨丢失并支持骨折愈合，但需要对成骨前体细胞的生物学特性进行操作。成骨细胞必须在传代扩增过程中保持其表型，但要经历一定数量的有丝分裂细胞周期才能产生合适的组织结构所需数量的细胞。这项拟议的研究将检查确保细胞保持有丝分裂后对骨表型的分子记忆的基本机制。我们研究的中心假设是，成骨因子的关键mRNAs在有丝分裂期间作为非基因组表观遗传机制的组成部分传递给子细胞，而选定的microRNAs(MiRs)减弱了这些传递的mRNAs的翻译。我们的假设是基于一组可靠的初步数据，这些数据表明成骨主控调控因子Runx2受成骨细胞系中有丝分裂的miRs控制。在这些和其他初步数据的基础上，我们将(I)鉴定在增殖的成骨细胞中抑制Runx2表达的miRs的全部组成，并开始鉴定有丝分裂期间的mRNAs和同源miRs；(Ii)检测miR在增殖的成骨细胞中细胞生长、存活和谱系方向方面依赖miR的变化，以及(Iii)表征选定的有丝分裂相关miRs在体内骨骼发育中的生理作用。对这一概念的验证将(I)在细胞周期调控中建立一个重要的新维度，(Ii)揭示在有丝分裂过程中miRs的一个先前未知的功能，(Iii)定义一种新的分子机制来生物控制有丝分裂细胞中的基因表达，以及(Iv)确定在有丝分裂时传递给成骨后代细胞的特定miRs(‘mito-miRs’)。从分子治疗的角度来看，这些MIR允许产生表观基因组制剂，通过靶向调节间充质干细胞扩张和分化的细胞命运决定因素来控制细胞遗传。 公共卫生相关性：骨形成需要骨祖细胞的扩增和分化。成骨细胞将遗传(染色体)和表观遗传信息(如CpG甲基化、组蛋白密码和转录因子的书签)传递给后代细胞，以维持生长潜力和成骨表型。我们将描述一种全新的基于RNA的表观遗传机制，涉及有丝分裂期间mRNAs和同源microRNAs的有丝分裂共传递。

DESCRIPTION (provided by applicant): Skeletal regenerative medicine promises to mitigate age-related bone loss and support fracture healing but requires manipulation of biological properties of osteogenic progenitor cells. Osteogenic cells must sustain their phenotype during lineage-expansion yet undergo a number of mitotic cell cycles to generate the requisite number of cells for proper tissue-organization. The proposed study will examine fundamental mechanisms that ensure cells retain a post-mitotic molecular memory of the bone phenotype. The central hypothesis of our study is that key mRNAs for osteogenic factors are passed on to daughter cells during mitosis as a component of a non-genomic epigenetic mechanism and that selected microRNAs (miRs) attenuate the translation of these transmitted mRNAs. Our hypothesis is based on a robust set of preliminary data showing that the osteogenic master regulator Runx2 is controlled by mitotic miRs in osteoblastic cell lines. Based on these and other preliminary data, we will (i) characterize the full complement of miRs that suppress expression of Runx2 in proliferating osteogenic cells, as well as begin characterization of mRNAs and cognate miRs during mitosis; (ii) examine miR dependent changes in fidelity of cell growth, survival and lineage-direction in proliferating osteoblasts, and (iii) characterize the physiological role of selected mitosis-related miRs during skeletal development in vivo. Validation of this concept would (i) establish a major new dimension in cell cycle regulation, (ii) reveal a previously unrecognized function for miRs during mitosis, (iii) define a novel molecular mechanism for biological control of gene expression in lineage-committed cells, and (iv) identify specific miRs that are transmitted to osteogenic progeny cells upon mitosis ('mito-miRs'). From a molecular therapeutic perspective, these miRs permit generation of epigenomic agents that control cellular inheritance by targeting cell fate determining factors which mediate mesenchymal stem cell expansion and differentiation. PUBLIC HEALTH RELEVANCE: Bone formation requires expansion and differentiation of osteoprogenitor cells. Osteogenic cells pass on genetic (chromosomes) and epigenetic information (e.g., CpG methylation, histone codes and bookmarking by transcription factors) to progeny cells to maintain growth potential and osteogenic phenotype identity. We will characterize a fundamentally novel RNA based epigenetic mechanism involving mitotic co-transmission of mRNAs and cognate microRNAs during mitosis.