Kruppel-like factor 4 regulates membranous and endochondral ossification
Kruppel-like factor 4 regulates membranous and endochondral ossification
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DOI：
10.1016/j.yexcr.2011.12.013
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发表时间：
2012-02-15
影响因子：
3.7
通讯作者：
Abe, Makoto
中科院分区：
文献类型：
--
作者：
Michikami, Ikumi;Fukushi, Toshiya;Abe, Makoto
Kruppel-like factor4(KLF4/GKLF/EZF)是一种锌指型转录因子，在皮肤、肠道、睾丸、肺和骨骼中高度表达。KLF4在正常上皮发育和维持中的作用已被广泛研究，但其在骨细胞中的作用尚不清楚。以往的报道表明，KLF4在发育中的扁平骨中有表达，但在出生后表达减弱。我们现在展示了在发育中的长骨中。KLF4在软骨膜、小梁成骨细胞和肥大前期软骨细胞中表达。相反，骨领表面的成骨细胞表现出极低水平的KLF4表达。为了研究KLF4在骨骼发育中的可能作用，我们建立了在鼠I型胶原调节序列下表达KLF4的转基因小鼠。转基因小鼠出现严重的骨骼畸形，并在出生后不久死亡。转基因小鼠显示颅骨形成延迟；在原代培养的小鼠颅骨成骨细胞中过表达KLF4导致矿化被强烈抑制，表明KLF4的这种调节是通过成骨细胞自主作用实现的。令人惊讶的是，转基因小鼠的长骨表现出骨髓腔形成的延迟。即使在E18.5时，假想的骨髓空间也被软骨原骨占据，很少观察到血管内皮细胞和破骨细胞的入侵。在转基因小鼠中，破骨细胞没有进入软骨原基，而是聚集在骨膜上。值得注意的是，骨钙素，已知的化学作用破骨细胞，在突变体中早在El4.5就在棘周处上调。体外研究表明，KLF4对骨钙素的诱导是在转录水平上进行调节的。我们的结果表明，KLF4通过协调成骨细胞、软骨细胞、血管内皮细胞和破骨细胞的分化和迁移来调节正常的骨骼发育。(C)2011 Elsevier Inc.保留所有权利。
Kruppel-like factor 4 (KLF4/GKLF/EZF) is a zinc finger type of transcription factor highly expressed in the skin, intestine, testis, lung and bone. The role played by Klf4 has been studied extensively in normal epithelial development and maintenance; however, its role in bone cells is unknown. Previous reports showed that Klf4 is expressed in the developing flat bones but its expression diminishes postnatally. We now show that in the developing long bones. Klf4 is expressed in the perichondrium, trabecular osteoblasts and prehypertrophic chondrocytes. In contrast, osteoblasts lining at the surface of the bone collar showed extremely low levels of Klf4 expression. To investigate the possible roles played by Klf4 during skeletal development, we generated transgenic mice expressing Klf4 under mouse type I collagen regulatory sequence. Transgenic mice exhibited severe skeletal deformities and died soon after birth. Transgenic mice showed delayed formation of the calvarial bones; and over-expressing Klf4 in primary mouse calvarial osteoblasts in culture resulted in strong repression of mineralization indicating that this regulation of Klf4 is through an osteoblast-autonomous effect. Surprisingly, long bones of the transgenic mice exhibited delayed marrow cavity formation. Even at E18.5, the presumptive marrow space was occupied by cartilage anlage and invasion of the vascular endothelial cells and osteoclasts were seldom observed. Instead of entering the cartilage anlage, osteoclasts accumulated at the periosteum in the transgenic mice. Significantly, osteocalcin, which is known to chemotact osteoclasts, was up-regulated at the perichindrium as early as El4.5 in the mutants. In vitro studies showed that this induction of osteocalcin by Klf4 was regulated at its transcriptional level. Our results demonstrate that Klf4 regulates normal skeletal development through coordinating the differentiation and migration of osteoblasts, chondrocytes, vascular endothelial cells and osteoclasts. (C) 2011 Elsevier Inc. All rights reserved.