Physiology and Experimental Medicine Program, Hospital for Sick Children Research Institute, Toronto, Ontario, M5G 1X8 Canada.
Am J Respir Cell Mol Biol. 2010 May;42(5):615-25. doi: 10.1165/rcmb.2008-0390OC. Epub 2009 Jul 2.
The sonic hedgehog (Shh) signaling pathway is crucial for normal lung development. In the lung, epithelial-produced Shh signals via mesenchymal Gli1-3 transcription factors. Gli-null lung phenotypes suggest that Gli2 is the primary Gli transcription factor transducing Shh-regulated lung growth, although the mechanism has yet to be elucidated. To clarify the role of Gli2 during lung development, we overexpressed gli2 in the lung mesenchyme of mice, to investigate for changes in Shh signaling, and cellular proliferation. The ectopic overexpression of gli2 resulted in increased Shh pathway activation as evident by increased expression of shh, ptc1, ptc2, smo, hhip, and gli1. Interestingly, we also observed increased expression of gli3 transcripts. Using two different mouse models, gli3-null and gli3Delta699 (Gli3 constitutive repressor), it was found that Gli3 activity does not affect the levels of gli2 in the developing lung. Real-time PCR and immunoblotting revealed that there is increased expression of cyclins D1, D2, and E1 associated with increased gli2 levels. Furthermore, the increase and decrease of cyclins (associated with changes in gli2 levels) positively correlated with cellular proliferation, as assessed by phospho-histone H3 immunohistochemistry. To determine if Gli3 has an effect on cyclin expression in the developing lung, we measured the levels of cyclin D1, D2, and E1, in gli3-null and gli3Delta699 mice and compared them to their wild-type counterparts. However, no change in the levels of cyclins D1, D2, or E1 due to altered Gli3 was observed. These findings suggest that Gli2 and not Gli3 is the primary mediator of Shh signaling influencing fetal lung growth through cyclin regulation.
声波刺猬（Shh）信号通路对于正常肺发育至关重要。在肺中，上皮细胞产生的 Shh 通过间质Gli1-3 转录因子发出信号。Gli 缺失的肺表型表明 Gli2 是主要的 Gli 转录因子，可将 Shh 调节的肺生长转导，尽管其机制尚未阐明。为了阐明 Gli2 在肺发育过程中的作用，我们在小鼠肺间质中过表达了 gli2，以研究 Shh 信号和细胞增殖的变化。Gli2 的异位过表达导致 Shh 通路的激活增加，这表现在 shh、ptc1、ptc2、 smo、hhip 和 gli1 的表达增加。有趣的是，我们还观察到 gli3 转录物的表达增加。使用两种不同的小鼠模型，gli3 缺失和 gli3Delta699（Gli3 组成型抑制剂），发现 Gli3 活性不影响发育中的肺中 gli2 的水平。实时 PCR 和免疫印迹显示，与 gli2 水平增加相关，存在细胞周期蛋白 D1、D2 和 E1 的表达增加。此外，细胞周期蛋白（与 gli2 水平变化相关）的增加和减少与细胞增殖呈正相关，如磷酸化组蛋白 H3 免疫组织化学评估所示。为了确定 Gli3 是否对发育中的肺中细胞周期蛋白的表达有影响，我们测量了 gli3 缺失和 gli3Delta699 小鼠中细胞周期蛋白 D1、D2 和 E1 的水平，并将其与野生型小鼠进行了比较。然而，由于 Gli3 的改变，细胞周期蛋白 D1、D2 或 E1 的水平没有变化。这些发现表明，Gli2 而不是 Gli3 是主要的 Shh 信号转导介质，通过细胞周期蛋白调节影响胎儿肺生长。
