Abstract：
Osteogenic differentiation plays important roles in the pathogenesis of osteoporosis. In this study, we explored the regulatory mechanism of histone methyltransferase SET domain bifurcated 1 (SETDB1) underlying the osteogenic differentiation in osteoporosis. The common osteoporosis-related genes were retrieved from the GeneCards, CTD, and Phenolyzer databases. The enrichment analysis was conducted on the candidate osteoporosis-related genes using the PANTHER software, and the binding site between transcription factors and target genes predicted by hTFtarget. The bioinformatics analyses suggested 6 osteoporosis-related chromatin/chromatin binding protein or regulatory proteins (HDAC4, SIRT1, SETDB1, MECP2, CHD7, and DKC1). Normal and osteoporosis tissues were collected from osteoporosis patients to examine the expression of SETDB1. It was found that SETDB1 was poorly expressed in osteoporotic femoral tissues, indicating that SETDB1 might be involved in the development of osteoporosis. We induced SETDB1 overexpression/knockdown, orthodenticle homeobox 2 (OTX2) overexpression, activation of Wnt/β-catenin or BMP-Smad pathways alone or in combination in osteoblasts or ovariectomized mice. The data indicated that SETDB1 methylation regulated H3K9me3 in the OTX2 promoter region and inhibited the expression of OTX2. Besides, the BMP-Smad and Wnt/β-catenin pathways were inhibited by OTX2, thereby resulting in inhibited osteogenic differentiation. Animal experiments showed that overexpressed SETDB1 could promote the increase of calcium level and differentiation of femoral tissues. In conclusion, upregulation of SETDB1 promotes osteogenic differentiation by inhibiting OTX2 and activating the BMP-Smad and Wnt/β-catenin pathways in osteoporosis.
摘要：
成骨分化在骨质疏松的发病机制中起重要作用。在这项研究中,我们探讨了组蛋白甲基转移酶SET结构域分叉1（SETDB1）在骨质疏松症成骨分化中的调控机制。从GeneCards检索常见的骨质疏松症相关基因，CTD,和Phenolyzer数据库。利用PANTHER软件对候选骨质疏松相关基因进行富集分析,以及hTFtarget预测的转录因子与靶基因之间的结合位点。生物信息学分析提示6种骨质疏松症相关染色质/染色质结合蛋白或调节蛋白（HDAC4、SIRT1、SETDB1、MECP2、CHD7和DKC1）。收集骨质疏松症患者的正常组织和骨质疏松症组织以检查SETDB1的表达。发现SETDB1在骨质疏松性股骨组织中表达不良，提示SETDB1可能参与了骨质疏松症的发生发展。我们诱导SETDB1过表达/敲低，正统同源盒2(OTX2)过表达，在成骨细胞或卵巢切除小鼠中单独或联合激活Wnt/β-catenin或BMP-Smad途径。数据表明SETDB1甲基化调节OTX2启动子区的H3K9me3并抑制OTX2的表达。此外,OTX2抑制BMP-Smad和Wnt/β-catenin通路,从而抑制成骨分化。动物实验表明，SETDB1过表达可促进股骨组织钙水平升高和分化。总之,SETDB1的上调通过抑制OTX2和激活骨质疏松中的BMP-Smad和Wnt/β-catenin通路促进成骨分化。
