ROLES OF SOX C GENES IN SKELETOGENESIS

描述（由申请人提供）：本项目将揭示Sox4、Sox11和Sox12在体内成骨细胞中的作用。这三个高度相关的蛋白构成了sry相关HMG box （Sox）转录因子的C亚家族。它们的基因在整个小鼠胚胎的成骨间充质细胞中共表达，并在这些细胞经历软骨细胞和成骨细胞分化时保持差异表达。虽然Sox12在体内的作用尚不清楚，但缺乏Sox4和/或Sox11的小鼠已经开始揭示这两个基因在骨骼形成的多个步骤中的重要作用。soxc蛋白的分子作用在很大程度上仍然未知，但初步研究表明，它们可能与DNA结合并激活转录，但效率不同。这些数据提出了一种假设，即Sox C蛋白在控制成骨细胞的命运和分化中可能具有冗余、互补或不同的分子作用。为了验证这一假设，目的1是进一步研究Sox C蛋白在小鼠胚胎骨骼形成中的作用。携带Sox11和Sox12条件空等位基因的小鼠将使用与产生Sox4条件空等位基因相同的策略产生。成熟的Cre转基因将用于在整个胚胎中或在骨骼形成过程中的特定步骤特异性地灭活基因。骨骼缺损将在形态学、细胞和分子水平上进行表征，并进行原代细胞培养实验，以补充体内研究。目的2是表征soxc蛋白在成骨细胞中的分子作用。三种Sox C蛋白的dna结合和转激活特性将通过标准体外和细胞培养实验进一步研究。通过基因表达阵列筛选确定潜在的靶基因。soxc蛋白对靶基因调控序列的作用将在体外和体内通过dna结合和反激活试验进行研究。预计这项研究将确定Sox C蛋白在特定细胞系中从多能前体阶段到晚期成熟的成骨细胞中是必不可少的决定因素，从而将为正常骨骼形成以及骨骼遗传和获得性疾病的分子机制提供重要见解。

DESCRIPTION (provided by applicant): This project will uncover the roles of Sox4, Sox11, and Sox12 in skeletogenic cells in vivo. These three highly related proteins form the subfamily C of Sry-related HMG box (Sox) transcription factors. Their genes are co-expressed in skeletogenic mesenchymal cells throughout the mouse embryo, and remain differentially expressed when these cells undergo chondrocyte and osteoblast differentiation. While the roles of Sox12 in vivo remain unknown, mice lacking Sox4 and/or Sox11 have started to reveal important roles for these two genes in multiple steps of skeletogenesis. The molecular roles of Sox C proteins remain largely unknown, but preliminary studies have suggested that they may bind DNA and activate transcription similarly but with different efficiencies. These data raise the hypothesis that Sox C proteins may have redundant, complementary, or distinct molecular roles in controlling skeletogenic cell fate and differentiation. To test this hypothesis, Aim 1 is to further study the roles of the Sox C proteins in mouse embryo skeletogenesis. Mice carrying Sox11 and Sox12 conditional null alleles will be generated using the same strategy that was used to generate a Sox4 conditional null allele. Well-established Cre transgenes will be used to specifically inactivate the genes in the entire embryo or at specific steps during skeletogenesis. Skeletal defects will be characterized at the morphological, cellular and molecular levels, and primary cell culture experiments will be carried out to complement in vivo studies. Aim 2 is to characterize the molecular roles of Sox C proteins in skeletogenic cells. The DNA-binding and transactivation properties of the three Sox C proteins will be further studied using standard in vitro and cell culture assays. Potential target genes will be identified by gene expression array screening. The action of Sox C proteins on target gene regulatory sequences will be studied using DNA-binding and transactivation assays in vitro and in vivo. It is anticipated that this study will identify Sox C proteins as essential determinants of skeletogenic cells from pluripotent precursor stages until late maturation in specific cell lineages, and will thereby provide significant insights into molecular mechanisms involved in normal skeletogenesis and in genetic and acquired diseases of the skeleton.