Cluster for Craniofacial Development and Regeneration Research, Institute of Oral Biosciences and Brain Korea 21 Program, Chonbuk National University, Jeonju 561-756, Korea.
Mol Cells. 2012 Oct;34(4):399-405. doi: 10.1007/s10059-012-0186-z. Epub 2012 Sep 15.
Sonic hedgehog (Shh) signaling regulates patterning, proliferation, and stem cell self-renewal in many organs. Smoothened (Smo) plays a key role in transducing Shh signaling into the nucleus by activating a glioma family of transcription factors; however, the cellular and molecular mechanisms underlying the role of sustained Smo activation in postnatal development are still unclear. In this study, we explored the effects of Shh signaling on bone development using a conditional knock-in mouse model that expresses a constitutively activated form of Smo (SmoM2) upon osteocalcin (OCN)-Cre-mediated recombination (SmoM2; OCN-Cre mice). We also evaluated the expression pattern of bone formation-related factors in primary calvarial cultures of mutant and control mice. The SmoM2; OCN-Cre mutant showed growth retardation and reduction of bone mineral density compared to control mice. Constitutively activated SmoM2 also repressed mRNA expression of Runx2, osterix, type I collagen, and osteocalcin. Further, sustained SmoM2 induction suppressed mineralization in calvarial primary osteoblasts cultures, whereas such induction did not affect cell proliferation in the mutant cultures as compared with SmoM2 only control cultures. These results suggest that sustained Smo activation inhibits postnatal development of bone by suppressing gene expression of bone formation regulatory factors in mice.
声波刺猬（Shh）信号在许多器官中调节着模式形成、增殖和干细胞自我更新。Smoothened（Smo）在将 Shh 信号转导到细胞核中起着关键作用，通过激活神经胶质瘤家族的转录因子；然而，持续激活 Smo 在出生后发育中的作用的细胞和分子机制仍不清楚。在这项研究中，我们使用一种条件性敲入小鼠模型来研究 Shh 信号对骨骼发育的影响，该模型在骨钙蛋白（OCN）-Cre 介导的重组时表达一种组成型激活形式的 Smo（SmoM2）（SmoM2；OCN-Cre 小鼠）。我们还评估了突变体和对照小鼠原代颅骨培养物中与骨形成相关的因子的表达模式。与对照小鼠相比，SmoM2；OCN-Cre 突变体表现出生长迟缓和骨密度降低。组成型激活的 SmoM2 还抑制了 Runx2、osterix、I 型胶原和骨钙蛋白的 mRNA 表达。此外，在颅骨原代成骨细胞培养物中，持续诱导 SmoM2 抑制了矿化，而与 SmoM2 仅对照培养物相比，这种诱导对突变体培养物中的细胞增殖没有影响。这些结果表明，在小鼠中，持续的 Smo 激活通过抑制骨形成调节因子的基因表达来抑制骨骼的出生后发育。
