Expression of OCZF directed by the cathepsin K promoter affects bone mass and osteoclast formation in Transgenic Mice.

OCZF基因产物是POK蛋白家族的成员，在其N-末端和C-末端分别含有POZ/BTB和锌指两个结构域，参与多种细胞过程。反义RNA抑制OCZF在体外可抑制破骨细胞分化，提示OCZF参与破骨细胞的形成，但在体内的作用尚不清楚。为此，我们建立了转基因小鼠，在小鼠组织蛋白K启动子(CTSK-OCZF)的控制下表达OCZF。通过对小鼠尾部基因组DNA的聚合酶链式反应和Southern杂交分析，在后代中鉴定出9只转基因小鼠。用10周龄骨髓体外分化的破骨细胞进行RT-PCR检测转基因的表达。转基因动物中有两个品系表现出较高的转基因表达，并进行了进一步的研究。对6周龄小鼠股骨进行显微CT和外周定量CT(PQCT)分析及组织形态计量学研究。Micro-CT成像显示转基因小鼠的骨小梁体积比正常小鼠的骨小梁体积减少。PQCT分析还显示骨密度和骨矿含量降低，尤其是小梁骨，强度应变指数降低，而皮质骨的影响较小。一致地，von Kossa染色显示转基因小鼠的矿化面积比正常小鼠小。抗酒石酸酸性磷酸酶染色和钙黄素标记的组织学分析表明，破骨细胞数量增加，而骨形成率没有明显变化。这些数据提示OCZF/LRF在体内破骨细胞形成中具有重要作用。

The OCZF gene product is a member of POK protein family that contains two domains of POZ/BTB and zinc finger in their N-and C-terminal region respectively, and that is shown to be involved in various cellular processes. Suppression of OCZF by antisense RNA inhibits osteoclast differentiation in vitro, indicating that OCZF is involved in osteoclastogenesis, but in vivo role in the process is not clear. To this end we generated transgenic mice, which expressed OCZF under the control of mouse cathepsin K promoter (Ctsk-OCZF). Nine transgenic mice were identified among the offspring by PCR and Southern blot analysis of mouse tail genomic DNA. Transgene expression was verified by RT-PCR using osteoclasts differentiated in vitro from bone marrow at 10 weeks of age. Two lines of the transgenic animals exhibited relatively high transgene expression, and were further investigated. Micro-CT and peripheral quantitative CT (pQCT) analyses and histomorphometry of femur were performed in mice at 6 weeks of age. Micro-CT imaging demonstrates a reduction in trabecular bone volume in the transgenic mice relative to normal littermates. pQCT analyses also demonstrate a reduction in bone mineral density and bone mineral content especially in trabecular bone with a decrease in strength strain index, whereas those in cortical bone were slightly affected. Consistently, von Kossa staining shows a smaller mineralized area in the transgenic mice than in normal littermates. Histological analyses with tartrate-resistant acid phosphatase staining and calcein labeling indicate an increase in the number of osteoclast, whereas bone formation rate did not significantly change. These data suggest that OCZF/LRF has an important role in osteoclastogenesis in vivo.