Wang Li, Mishina Yuji, Liu Fei
Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, 48109, USA.
Calcif Tissue Int. 2015 Feb;96(2):129-37. doi: 10.1007/s00223-014-9945-5. Epub 2014 Dec 31.
The Cre/loxP system has been widely used to generate tissue-specific gene knockout mice. Inducible (Tet-off) Osx-GFP::Cre (Osx-Cre) mouse line that targets osteoblasts is widely used in the bone research field. In this study, we investigated the effect of Osx-Cre on craniofacial bone development. We found that newborn Osx-Cre mice showed severe hypomineralization in parietal, frontal, and nasal bones as well as the coronal sutural area when compared to control mice. As the mice matured, the intramembranous bone hypomineralization phenotype became less severe. The major hypomineralization defect in parietal, frontal, and nasal bones had mostly disappeared by postnatal day 21, but the defect in sutural areas persisted. Importantly, Doxycycline treatment eliminated cranial bone defects at birth which indicates that Cre expression may be responsible for the phenotype. In addition, we showed that the primary calvarial osteoblasts isolated from neonatal Osx-Cre mice had comparable differentiation ability compared to their littermate controls. This study reinforces the idea that Cre-positive litter mates are indispensable controls in studies using conditional gene deletion.
Cre/loxP系统已被广泛用于生成组织特异性基因敲除小鼠。靶向成骨细胞的诱导型（Tet-off）Osx-GFP::Cre（Osx-Cre）小鼠品系在骨研究领域被广泛使用。在本研究中，我们调查了Osx-Cre对颅面骨发育的影响。我们发现，与对照小鼠相比，新生Osx-Cre小鼠的顶骨、额骨、鼻骨以及冠状缝区域出现严重的矿化不足。随着小鼠成熟，膜内骨矿化不足的表型变得不那么严重。顶骨、额骨和鼻骨的主要矿化不足缺陷在出生后第21天大多消失，但缝合区域的缺陷仍然存在。重要的是，强力霉素治疗消除了出生时的颅骨缺陷，这表明Cre表达可能是造成该表型的原因。此外，我们表明，从新生Osx-Cre小鼠分离的原代颅骨成骨细胞与其同窝对照相比具有相当的分化能力。这项研究强化了这样一种观点，即在使用条件性基因缺失的研究中，Cre阳性的同窝仔是不可或缺的对照。
