Tanimoto Yukiho, Yokozeki Masahiko, Hiura Kenji, Matsumoto Kazuya, Nakanishi Hideki, Matsumoto Toshio, Marie Pierre J, Moriyama Keiji
Department of Orthodontics and Dentofacial Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8504, Japan.
J Biol Chem. 2004 Oct 29;279(44):45926-34. doi: 10.1074/jbc.M404824200. Epub 2004 Aug 13.
Apert syndrome is an autosomal dominant disease characterized by craniosynostosis and bony syndactyly associated with point mutations (S252W and P253R) in the fibroblast growth factor receptor (FGFR) 2 that cause FGFR2 activation. Here we investigated the role of the S252W mutation of FGFR2 on osteoblastic differentiation. Osteoblastic cells derived from digital bone in two Apert patients with the S252W mutation showed more prominent alkaline phosphatase activity, osteocalcin and osteopontin mRNA expression, and mineralized nodule formation compared with the control osteoblastic cells derived from two independent non-syndromic polydactyly patients. Stable clones of the human MG63 osteosarcoma cells (MG63-Ap and MG63-IIIc) overexpressing a splice variant form of FGFR2 with or without the S252W mutation (FGFR2IIIcS252W and FGFR2IIIc) showed a higher RUNX2 mRNA expression than parental MG63 cells. Furthermore MG63-Ap exhibited a higher osteopontin mRNA expression than did MG63-IIIc. The enhanced osteoblastic marker gene expression and mineralized nodule formation of the MG63-Ap was inhibited by the conditioned medium from the COS-1 cells overexpressing the soluble FGFR2IIIcS252W. Furthermore the FGF2-induced osteogenic response in the mouse calvarial organ culture system was blocked by the soluble FGFR2IIIcS252W. These results show that the S252W mutation in the FGFR2 gene enhances the osteoblast phenotype in human osteoblasts and that a soluble FGFR2 with the S252W mutation controls osteoblast differentiation induced by the S252W mutation through a dominant negative effect on FGFR2 signaling in Apert syndrome.
Apert综合征是一种常染色体显性疾病，其特征为颅缝早闭和骨性并指，与成纤维细胞生长因子受体（FGFR）2中的点突变（S252W和P253R）相关，这些突变会导致FGFR2激活。在此，我们研究了FGFR2的S252W突变对成骨细胞分化的作用。与来自两名独立的非综合征性多指患者的对照成骨细胞相比，两名携带S252W突变的Apert患者的指骨来源的成骨细胞表现出更显著的碱性磷酸酶活性、骨钙素和骨桥蛋白mRNA表达以及矿化结节形成。过表达带有或不带有S252W突变（FGFR2IIIcS252W和FGFR2IIIc）的FGFR2剪接变体形式的人MG63骨肉瘤细胞（MG63-Ap和MG63-IIIc）的稳定克隆显示，其RUNX2 mRNA表达高于亲代MG63细胞。此外，MG63-Ap的骨桥蛋白mRNA表达高于MG63-IIIc。过表达可溶性FGFR2IIIcS252W的COS-1细胞的条件培养基抑制了MG63-Ap增强的成骨细胞标记基因表达和矿化结节形成。此外，在小鼠颅骨器官培养系统中，FGF2诱导的成骨反应被可溶性FGFR2IIIcS252W阻断。这些结果表明，FGFR2基因中的S252W突变增强了人成骨细胞中的成骨细胞表型，并且带有S252W突变的可溶性FGFR2通过对Apert综合征中FGFR2信号传导的显性负效应来控制由S252W突变诱导的成骨细胞分化。
