Department of Molecular Pathology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
J Biochem. 2012 Jun;151(6):621-31. doi: 10.1093/jb/mvs022. Epub 2012 Feb 29.
Smad7 is an inhibitory molecule induced by members of the transforming growth factor-β (TGF-β) family, including TGF-β, activin, nodal and bone morphogenetic proteins (BMPs). To elucidate the in vivo functions of Smad7, we generated conditional Smad7-knockout mice in which the Mad homology 2 (MH2) domain and the poly (A) signal sequence were flanked with loxP sites (floxed). The Smad7-floxed mice exhibited no obvious phenotype. Smad7 total-null mice on a C57BL/6 background died within a few days of birth, whereas mice with an ICR background developed to adulthood but were significantly smaller than wild-type mice. Unexpectedly, phospho-Smad2 and phospho-Smad3 were decreased in Smad7-deficient mouse embryonic fibroblast (MEF) cells, whereas phospho-Smad1/5/8 was similarly expressed in wild-type and Smad7-deficient MEF cells. Moreover, expression levels of TGF-β type I receptor (ALK5) were higher in Smad7-deficient MEF cells than in wild-type MEF cells. Plasminogen activator inhibitor-1 (PAI-1) and inhibitor of differentiation-1 (Id-1) mRNA were similarly expressed in wild-type and Smad7-deficient MEF cells. Some differences were observed in mitogen-activated protein kinase (MAPK)-signalling between wild-type and Smad7-deficient MEF cells. We demonstrated that Smad7 plays an important role in normal mouse growth and provide a useful tool for analysing Smad7 functions in vivo.
Smad7 是转化生长因子-β（TGF-β）家族成员诱导的抑制分子，包括 TGF-β、激活素、 nodal 和骨形态发生蛋白（BMPs）。为了阐明 Smad7 的体内功能，我们在 Mad 同源结构域 2（MH2）和多聚（A）信号序列的侧翼产生了条件性 Smad7 敲除小鼠，这些序列被loxP 位点（floxed）包围。Smad7 敲除小鼠没有表现出明显的表型。C57BL/6 背景下的 Smad7 完全缺失小鼠在出生后几天内死亡，而 ICR 背景下的小鼠发育到成年，但比野生型小鼠小得多。出乎意料的是，Smad7 缺失的小鼠胚胎成纤维细胞（MEF）细胞中的磷酸化 Smad2 和磷酸化 Smad3 减少，而野生型和 Smad7 缺失的 MEF 细胞中磷酸化 Smad1/5/8 的表达相似。此外，Smad7 缺失的 MEF 细胞中 TGF-β Ⅰ型受体（ALK5）的表达水平高于野生型 MEF 细胞。纤溶酶原激活物抑制剂-1（PAI-1）和分化抑制因子-1（Id-1）mRNA 在野生型和 Smad7 缺失的 MEF 细胞中的表达相似。野生型和 Smad7 缺失的 MEF 细胞之间的丝裂原激活蛋白激酶（MAPK）信号转导存在一些差异。我们证明 Smad7 在正常小鼠生长中发挥重要作用，并为体内分析 Smad7 功能提供了有用的工具。
