The transcription factor Snail regulates osteogenic differentiation by repressing Runx2 expression

Abstract

[한글]

[영문]Osteoblasts originate from mesenchymal stem cells by the coordinated activities of different signaling pathways that regulate the expression of osteoblast-specific genes. Runt-related transcription factor 2 (Runx2) is the master transcription factor for osteoblast differentiation. Despite the importance of Runx2 in the developing skeleton, how Runx2 expression is regulated remains a pivotal question. Snail, a zinc-finger transcription factor, is involved in a broad spectrum of biological functions such as cell differentiation, cell cycle regulation, and apoptosis. However, it is not clear how Snail functions in osteogenic differentiation. Therefore, in this study, the functional role of Snail in osteogenic differentiation was investigated using an integrated molecular physiological approach and zebrafish models for in vivo studies. Snail was expressed highly in C3H10T1/2 mesenchymal stem cells and C2C12 premyoblastic cells. And, interestingly, the expression level of Snail gradually decreased during progression of osteoblast differentiation. Neither the overexpression nor the knockdown of Snail in C3H10T1/2 cells and MC3T3-E1 preosteoblastic cells affected cell proliferation. However, Runx2 expression was significantly up- or down-regulated relative to Snail expression. Chromatin immunoprecipitation assay and electrophoretic mobility shift assay revealed that Snail binds to the Runx2 promoter and that repression of Runx2 transcription by Snail is dependent on specific E-box sequence within the promoter. In addition, osteogenic potential was significantly enhanced by antisense morpholino oligonucleotide-mediated knockdown of Snail expression in zebrafish. These results indicate that Snail plays a crucial role in osteogenic differentiation by acting as a direct Runx2 repressor.