Col1a1 promoter-targeted expression of p20 CCAAT enhancer-binding protein beta (C/EBPbeta), a truncated C/EBPbeta isoform, causes osteopenia in transgenic mice.
Col1a1 promoter-targeted expression of p20 CCAAT enhancer-binding protein beta (C/EBPbeta), a truncated C/EBPbeta isoform, causes osteopenia in transgenic mice.
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发表时间：
2005
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通讯作者：
J. Harrison;Yu-feng Huang;K. Wilson;P. Kelly;D. Adams;G. Gronowicz;S. Clark
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作者：
J. Harrison;Yu-feng Huang;K. Wilson;P. Kelly;D. Adams;G. Gronowicz;S. Clark
CCAAT增强子结合蛋白（C/EBP）转录因子调节脂肪细胞分化，最近的证据表明，成骨细胞和脂肪细胞在骨髓中共享一个共同的多能祖细胞。然而，很少有人知道的C/EBP转录因子在控制成骨细胞分化或功能的作用。在这项研究中，C/EBP转录因子的功能在成骨细胞系细胞中被破坏，通过过表达一种天然存在的显性负C/EBP亚型。FLp 20 C/EBP β的表达由3.6-kb Col 1a 1启动子/第一内含子构建体驱动，并建立了4个转基因（TG）小鼠系。北方印迹和逆转录-PCR表明，转基因靶向骨，在肺，皮肤和脂肪组织中的表达水平较低。来自两个品系的TG小鼠与野生型同窝小鼠相比显示体重减轻。所有TG系均显示骨质减少的证据，范围从轻度到重度，表现为骨小梁体积减少。严重受累的行也显示皮质骨宽度减少。动态组织形态测定表明，矿物质沉积和骨形成率下降。TG小鼠的长骨和颅骨显示COL 1A 1和骨钙素mRNA水平降低，骨唾液酸蛋白mRNA增加，与终末成骨细胞分化的抑制一致。原代成骨细胞分化的离体分析显示出对标记物表达的类似作用，并且成熟成骨细胞标记物Col2.3-绿色荧光蛋白的表达降低，证明了转基因的细胞自主作用。这些数据表明，C/EBP转录因子可能是成骨细胞功能和骨量的重要决定因素。
CCAAT enhancer-binding protein (C/EBP) transcription factors regulate adipocyte differentiation, and recent evidence suggests that osteoblasts and adipocytes share a common pluripotent progenitor in bone marrow. However, little is known about the role of C/EBP transcription factors in the control of osteoblast differentiation or function. In this study, the function of C/EBP transcription factors was disrupted in osteoblast lineage cells by overexpressing a naturally occurring dominant negative C/EBP isoform. Expression of FLp20C/EBPbeta was driven by a 3.6-kb Col1a1 promoter/first intron construct, and four transgenic (TG) mouse lines were established. Northern blotting and reverse transcription-PCR indicated that the transgene was targeted to bone, with lower levels of expression in lung, skin, and adipose tissue. TG mice from two lines showed reduced body weight compared with wild type littermates. All TG lines showed evidence of osteopenia, ranging from mild to severe, as evidenced by reduced trabecular bone volume. Severely affected lines also showed reduced cortical bone width. Dynamic histomorphometry demonstrated an associated decrease in mineral apposition and bone formation rates. Long bones and calvariae of TG mice showed reduced COL1A1 and osteocalcin mRNA levels and increased bone sialoprotein mRNA, consistent with an inhibition of terminal osteoblast differentiation. Ex vivo analysis of primary osteoblast differentiation showed similar effects on marker expression and reduced expression of the mature osteoblast marker Col2.3-green fluorescent protein, demonstrating a cell-autonomous effect of the transgene. These data suggested that C/EBP transcription factors may be important determinants of osteoblast function and bone mass.