Tamoxifen-inducible gene deletion reveals a distinct cell type associated with trabecular bone, and direct regulation of PTHrP expression and chondrocyte morphology by Ihh in growth region cartilage
Tamoxifen-inducible gene deletion reveals a distinct cell type associated with trabecular bone, and direct regulation of PTHrP expression and chondrocyte morphology by Ihh in growth region cartilage
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DOI：
10.1016/j.ydbio.2007.05.011
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发表时间：
2007-08-01
影响因子：
2.7
通讯作者：
Long, Fanxin
中科院分区：
文献类型：
--
作者：
Hilton, Matthew J.;Tu, Xiaolin;Long, Fanxin
印度刺猬 (Ihh) 通过向软骨细胞和软骨膜细胞发出信号来控制软骨内骨骼发育的多个方面。之前通过 Col2-Cre 介导的 Smoothened（Smo，编码 Ihh 信号传导所必需的跨膜蛋白）消融来描述 Ihh 对软骨细胞的直接影响的努力仅取得了部分成功，因为无法区分软骨细胞和软骨膜细胞。在这里，我们报道了一个转基因品系（Col2-Cre（TM）），该品系在 Cola I（H）启动子的控制下表达惰性形式的 Cre，可被外源 tarnoxifen（TM）激活；在胚胎发生过程中的适当时间施用TM会诱导软骨细胞中的Cre活性，但不会诱导软骨膜中的Cre活性。通过使用该小鼠品系，我们在不影响软骨膜的情况下删除了软骨细胞子集中的 Smo，并发现 Smo 的删除导致甲状旁腺激素相关蛋白 (PTIHrP) 的表达和软骨细胞形态的局部破坏。出乎意料的是，TM 总是在与长骨小梁骨表面相关的细胞子集中诱导 Cre 活性。这些细胞经过基因标记并在体外培养后能够产生骨结节。这些细胞中 Col2-Cre (TM) 转基因的表达可能反映了内源性 Cola 1 (11) 启动子活性，因为发现类似的细胞内源性表达 Cola I (II) mRNA 的 11A 同工型。总之，本研究不仅提供了 Ihh 信号传导直接控制生长区域软骨中 PTHrP 表达和软骨细胞形态的证据，而且还发现了与小梁骨相关的独特细胞类型，该细胞类型似乎具有成骨潜力。 (c) 2007 Elsevier Inc. 保留所有权利。
Indian hedgehog (Ihh) controls multiple aspects of endochondral skeletal development by signaling to both chondrocytes and perichondrial cells. Previous efforts to delineate direct effects of Ihh on chondrocytes by Col2-Cre-inediated ablation of Smoothened (Smo, encoding a transmembrane protein indispensable for Ihh signaling) has been only partially successful, due to the inability to discriminate between chondrocytes and perichondrial cells. Here we report a transgenic line (Col2-Cre (TM)) expressing under the control of the Cola I (H) promoter an inert form of Cre that is activatable by exogenous tarnoxifen (TM); TM administration at proper times during embryogenesis induced Cre activity in chondrocytes but not in the perichondrium. By using this mouse line, we deleted Smo within subsets of chondrocytes without affecting the perichondrium and found that Smo removal led to localized disruption of the expression of parathyroid hormone-related protein (PTIHrP) and the morphology of chondrocytes. Unexpectedly, TM invariably induced Cre activity in a subset of cells associated with the trabecular bone surface of long bones. These cells, when genetically marked and cultured in vitro, were capable of producing bone nodules. Expression of the Col2-Cre (TM) transgene in these cells likely reflected the endogenous Cola 1 (11) promoter activity as similar cells were found to express the 11A isoform of Cola I (II) mRNA endogenously. In summary, the present study has not only provided evidence that Ihh signaling directly controls PTHrP expression and chondrocyte morphology in the growth region cartilage, but has also uncovered a distinct cell type associated with the trabecular bone that appears to possess osteogenic potential. (c) 2007 Elsevier Inc. All rights reserved.