The Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
J Cell Biochem. 2011 Feb;112(2):653-65. doi: 10.1002/jcb.22968.
Runx2 is a transcription factor controlling skeletal development, and is also expressed in extraskeletal tissues where its function is not well understood. Existing Runx2 mutant and transgenic mouse models do not allow the necessary control of Runx2 expression to understand its functions in different tissues. We generated conditional, doxycyline-inducible, triple transgenic mice (CMV-Cre;ROSA26-neo(flox/+)-rtTA;Tet-O-Runx2) to investigate the effects of wide spread overexpression of Runx2. Osteoblasts isolated from CMV-Cre;ROSA26-neo(flox/+)-rtTA; Tet-O-Runx2 mice demonstrated a dose-dependent effect of doxycycline to stimulate Runx2 transgene expression. Doxycycline administration to CMV-Cre;ROSA26-neo(flox/+)-rtTA;Tet-O-Runx2 mice induced Runx2 transgene expression in all tissues tested, with the highest levels observed in kidney, ovary, and bone. Runx2 overexpression resulted in deceased body size and reduced viability. With regard to bone, Runx2 overexpressing mice paradoxically displayed profound osteopenia and diminished osteogenesis. Induced expression of Runx2 in extraskeletal tissues resulted in ectopic calcification and induction of the osteogenic program in a limited number of tissues, including lung and muscle. In addition, the triple transgenic mice showed evidence of a myeloproliferative disorder and an apparent inhibition of lymphocyte development. Thus, overexpression of Runx2 both within and outside of the skeleton can have diverse biological effects. Use of tissue specific Cre mice will allow this model to be used to conditionally and inducibly overexpress Runx2 in different tissues and provide a means to study the post-natal tissue- and cell context-dependent functions of Runx2.
Runx2 是一种转录因子，控制骨骼发育，也在骨骼外组织中表达，但其功能尚未完全了解。现有的 Runx2 突变体和转基因小鼠模型不能很好地控制 Runx2 的表达，从而无法了解其在不同组织中的功能。我们生成了条件性、强力霉素诱导型、三重转基因小鼠（CMV-Cre；ROSA26-neo(flox/+)-rtTA；Tet-O-Runx2），以研究 Runx2 广泛过表达的影响。从 CMV-Cre；ROSA26-neo(flox/+)-rtTA；Tet-O-Runx2 小鼠分离的成骨细胞表现出强力霉素剂量依赖性地刺激 Runx2 转基因表达的作用。强力霉素给药于 CMV-Cre；ROSA26-neo(flox/+)-rtTA；Tet-O-Runx2 小鼠，在所有测试的组织中诱导 Runx2 转基因表达，在肾脏、卵巢和骨骼中观察到最高水平。Runx2 过表达导致体型减小和活力降低。就骨骼而言，Runx2 过表达小鼠反常地表现出严重的骨质疏松和成骨作用降低。在骨骼外组织中诱导 Runx2 表达导致异位钙化和少数组织中骨生成程序的诱导，包括肺和肌肉。此外，三重转基因小鼠显示出骨髓增生异常的证据，以及淋巴细胞发育明显受到抑制。因此，Runx2 在骨骼内外的过表达都可能具有多种生物学效应。使用组织特异性 Cre 小鼠将使该模型能够在不同组织中条件性和诱导性地过表达 Runx2，并提供一种研究 Runx2 在出生后组织和细胞背景依赖性功能的方法。
