The Wnt antagonist Frzb-1 regulates chondrocyte maturation and long bone development during limb skeletogenesis
The Wnt antagonist Frzb-1 regulates chondrocyte maturation and long bone development during limb skeletogenesis
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DOI：
10.1006/dbio.2002.0802
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发表时间：
2002-11-01
影响因子：
2.7
通讯作者：
Iwamoto, M
中科院分区：
文献类型：
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作者：
Enomoto-Iwamoto, M;Kitagaki, J;Iwamoto, M
Wnt拮抗剂Frzb-1在肢体骨骼发育过程中表达，但其在这一复杂的多步骤过程中的作用尚未完全了解。为了解决这个问题，我们确定了鸡长骨发育过程中Frzb-1基因的表达模式，并通过Frzb-1，Wnt-8（一种已知的Frzb-1靶标）或不同形式的细胞内Wnt介体LEF-1在发育肢体和培养的软骨细胞中的错误表达进行了功能获得和功能丧失的研究。Frzb-1的表达是相当强的间充质prechondrogenic凝聚，然后表征骺关节软骨细胞和生长板中的prehypertrophic软骨细胞。重要驱动的Frzb-1错误表达导致骨骼元素缩短、关节融合和软骨细胞成熟延迟，从而抑制基质矿化、金属蛋白酶表达和骨髓/骨形成。在良好的协议，错误表达的Frzb-1或显性阴性形式的LEF-1在培养的软骨细胞保持在一个不成熟的阶段的细胞。相反，Wnt-8或组成型活性LEF-1的错误表达强烈促进软骨细胞成熟、肥大和钙化。免疫组化染色显示，内源性Wnt介质β-连环蛋白的分布在体内和体外发生了显着变化，主要是从未成熟的增殖和prehypertrophic软骨细胞的细胞质到肥大的矿化软骨细胞的细胞核。在体内或体外，Frzb-1的错误表达阻止了β-连环蛋白在软骨细胞中的核重定位。这些数据表明，Frzb-1对肢体骨骼发育有很强的影响，是软骨细胞成熟、表型和功能的强大而直接的调节剂。骨骼发生的阶段，如终末软骨细胞成熟和关节形成，似乎特别依赖于Wnt信号传导，因此对Frzb-1拮抗作用非常敏感。(C)2002 Elsevier Science（美国）。
The Wnt antagonist Frzb-1 is expressed during limb skeletogenesis, but its roles in this complex multistep process are not fully understood. To address this issue, we determined Frzb-1 gene expression patterns during chick long bone development and carried out gain- and loss-of-function studies by misexpression of Frzb-1, Wnt-8 (a known Frzb-1 target), or different forms of the intracellular Wnt mediator LEF-1 in developing limbs and cultured chondrocytes. Frzb-1 expression was quite strong in mesenchymal prechondrogenic condensations and then characterized epiphyscal articular chondrocytes and prehypertrophic chondrocytes in growth plates. Vitally driven Frzb-1 misexpression caused shortening of skeletal elements, joint fusion, and delayed chondrocyte maturation, with consequent inhibition of matrix mineralization, metalloprotease expression, and marrow/bone formation. In good agreement, misexpression of Frzb-1 or a dominant-negative form of LEF-1 in cultured chondrocytes maintained the cells at an immature stage. Instead, misexpression of Wnt-8 or a constitutively active LEF-1 strongly promoted chondrocyte maturation, hypertrophy, and calcification. Immunostaining revealed that the distribution of endogenous Wnt mediator beta-catenin changes dramatically in vivo and in vitro, from largely cytoplasmic in immature proliferating and prehypertrophic chondrocytes to nuclear in hypertrophic mineralizing chondrocytes. Misexpression of Frzb-1 prevented beta-catenin nuclear relocalization in chondrocytes in vivo or in vitro. The data demonstrate that Frzb-1 exerts a strong influence on limb skeletogenesis and is a powerful and direct modulator of chondrocyte maturation, phenotype, and function. Phases of skeletogenesis, such as terminal chondrocyte maturation and joint formation, appear to be particularly dependent on Wnt signaling and thus very sensitive to Frzb-1 antagonistic action. (C) 2002 Elsevier Science (USA).