Camp Esther, Anderson Peter J, Zannettino Andrew C W, Gronthos Stan
Mesenchymal Stem Cell Laboratory, Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, South Australia, Australia; Cancer Theme, South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.
Australian Craniofacial Unit, Women's and Children's Hospital, North Adelaide, South Australia, Australia.
Bone. 2017 Jan;94:98-107. doi: 10.1016/j.bone.2016.09.019. Epub 2016 Sep 23.
The TWIST-1 gene encodes a basic helix-loop-helix (bHLH) transcription factor important in mediating skeletal and head mesodermal tissue development. Bone marrow-derived mesenchymal stem/stromal cells (BMSC), express high levels of TWIST-1, which is down regulated during ex vivo expansion. Cultured BMSC over-expressing TWIST-1 display decreased capacity for osteogenic differentiation and an enhanced capacity to undergo adipogenesis, suggesting that TWIST-1 is a mediator of lineage commitment. However, little is known regarding the mechanism(s) by which TWIST-1 mediates cell fate determination. In this study, microarray analysis was used to identify a novel downstream TWIST-1 target, tyrosine kinase receptor c-ros-oncogene 1 (C-ROS-1), which was down regulated in TWIST-1 over-expressing BMSC. Chromatin immunoprecipitation analysis showed that TWIST-1 directly bound to two E-box binding sites on the proximal C-ROS-1 promoter. Knock-down of C-ROS-1 in human BMSC and cranial bone cells resulted in a decreased capacity for osteogenic differentiation in vitro. Conversely, suppression of C-ROS-1 in BMSC resulted in an enhanced capacity to undergo adipogenesis. Furthermore, reduced C-ROS-1 levels led to activation of different components of the PI3K/AKT/mTORC1 signalling pathway during osteogenic and adipogenic differentiation. Collectively, these data suggest that C-ROS-1 is involved in BMSC fate switching between osteogenesis and adipogenesis, mediated via PI3K/AKT/mTORC1 signalling.
TWIST-1基因编码一种在介导骨骼和头部中胚层组织发育中起重要作用的碱性螺旋-环-螺旋（bHLH）转录因子。骨髓间充质干/基质细胞（BMSC）表达高水平的TWIST-1，其在体外扩增过程中下调。过表达TWIST-1的培养BMSC显示出成骨分化能力下降和脂肪生成能力增强，这表明TWIST-1是谱系定向的介导因子。然而，关于TWIST-1介导细胞命运决定的机制知之甚少。在本研究中，利用微阵列分析鉴定了一个新的TWIST-1下游靶点，酪氨酸激酶受体c-ros原癌基因1（C-ROS-1），其在过表达TWIST-1的BMSC中下调。染色质免疫沉淀分析表明，TWIST-1直接结合到近端C-ROS-1启动子上的两个E-box结合位点。在人BMSC和颅骨细胞中敲低C-ROS-1导致体外成骨分化能力下降。相反，在BMSC中抑制C-ROS-1导致脂肪生成能力增强。此外，降低C-ROS-1水平导致在成骨和脂肪生成分化过程中PI3K/AKT/mTORC1信号通路的不同组分激活。总的来说，这些数据表明C-ROS-1参与了BMSC在成骨和脂肪生成之间的命运转换，通过PI3K/AKT/mTORC1信号介导。
