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J Biol Chem ; 290(7): 3910-24, 2015 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-25538250

RESUMO

Menin, the product of the multiple endocrine neoplasia type 1 (Men1) tumor suppressor gene, mediates the cell proliferation and differentiation actions of transforming growth factor-ß (TGF-ß) ligand family members. In vitro, menin modulates osteoblastogenesis and osteoblast differentiation promoted and sustained by bone morphogenetic protein-2 (BMP-2) and TGF-ß, respectively. To examine the in vivo function of menin in bone, we conditionally inactivated Men1 in mature osteoblasts by crossing osteocalcin (OC)-Cre mice with floxed Men1 (Men1(f/f)) mice to generate mice lacking menin in differentiating osteoblasts (OC-Cre;Men1(f/f) mice). These mice displayed significant reduction in bone mineral density, trabecular bone volume, and cortical bone thickness compared with control littermates. Osteoblast and osteoclast number as well as mineral apposition rate were significantly reduced, whereas osteocyte number was increased. Primary calvarial osteoblasts proliferated more quickly but had deficient mineral apposition and alkaline phosphatase activity. Although the mRNA expression of osteoblast marker and cyclin-dependent kinase inhibitor genes were all reduced, that of cyclin-dependent kinase, osteocyte marker, and pro-apoptotic genes were increased in isolated Men1 knock-out osteoblasts compared with controls. In contrast to the knock-out mice, transgenic mice overexpressing a human menin cDNA in osteoblasts driven by the 2.3-kb Col1a1 promoter, showed a gain of bone mass relative to control littermates. Osteoblast number and mineral apposition rate were significantly increased in the Col1a1-Menin-Tg mice. Therefore, osteoblast menin plays a key role in bone development, remodeling, and maintenance.


Assuntos
Desenvolvimento Ósseo/fisiologia , Osso e Ossos/fisiologia , Diferenciação Celular , Osteoblastos/citologia , Proteínas Proto-Oncogênicas/fisiologia , Animais , Apoptose , Western Blotting , Densidade Óssea , Proteína Morfogenética Óssea 2/genética , Proteína Morfogenética Óssea 2/metabolismo , Proliferação de Células , Células Cultivadas , Feminino , Humanos , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Neoplasia Endócrina Múltipla Tipo 1/metabolismo , Osteoblastos/metabolismo , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais , Fator de Crescimento Transformador beta/genética , Fator de Crescimento Transformador beta/metabolismo
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