Bone Cell Growth Regulation by Runx2/Cbfa1

描述（由申请人提供）：骨再生医学有望减轻与年龄相关的骨丢失并支持骨折愈合，但需要操纵成骨祖细胞的生物学特性。成骨细胞在谱系扩增期间必须维持其表型，但仍经历许多有丝分裂细胞周期以产生适当组织组织所需的细胞数量。这项研究将检查确保细胞保留骨表型的有丝分裂后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mRNA在有丝分裂期间作为非基因组表观遗传机制的一个组成部分传递给子细胞，并且所选择的microRNA（miRs）减弱这些传递的mRNA的翻译。我们的假设是基于一组可靠的初步数据，表明成骨细胞系中成骨主调节因子Runx 2受有丝分裂miR控制。基于这些和其他初步数据，我们将（i）表征增殖的成骨细胞中抑制Runx 2表达的全部miR，以及开始有丝分裂期间mRNA和同源miR的表征;（ii）检查增殖成骨细胞中细胞生长、存活和谱系方向的保真度的miR依赖性变化，和（iii）表征所选有丝分裂相关miR在体内骨骼发育期间的生理作用。这一概念的验证将（i）建立细胞周期调控中的主要新维度，（ii）揭示miR在有丝分裂期间的先前未被认识的功能，（iii）定义用于谱系定型细胞中基因表达的生物控制的新分子机制，以及（iv）鉴定在有丝分裂后传递到成骨子代细胞的特异性miR（“有丝分裂-miR”）。从分子治疗的角度来看，这些miR允许产生表观基因组试剂，其通过靶向介导间充质干细胞扩增和分化的细胞命运决定因子来控制细胞遗传。

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.