Distribution, gene expression, and functional role of EphA4 during ossification.
EphA4 receptor tyrosine kinase has been shown to be critically involved in neural tissue development. Here, we found EphA4 was also distributed among hypertrophic chondrocytes and osteoblasts in the growth plate of developing mouse long bones. In vitro evaluation revealed that ephA4 expression was elevated upon hypertrophic differentiation of chondrocytes and that markedly stronger expression was observed in osteoblastic SaOS-2 than chondrocytic HCS-2/8 cells. Of note, RNAi-mediated silencing of ephA4 in SaOS-2 cells resulted in the repression of osteocalcin gene expression and alkaline phosphatase activity. Interestingly, confocal laser-scanning microscopic analysis revealed the presence of EphA4 molecules in the nucleus as well as on the surface of SaOS-2 cells. These findings are the first indication of a critical role of EphA4 in ossification, especially at the final stage in which osteoblasts and hypertrophic chondrocytes play major roles.
Kuroda
Chisa
C
Department of Biochemistry and Molecular Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama 700-8525, Japan.
Kubota
Satoshi
S
Kawata
Kazumi
K
Aoyama
Eriko
E
Sumiyoshi
Kumi
K
Oka
Morihiko
M
Inoue
Miho
M
Minagi
Shogo
S
Takigawa
Masaharu
M
D000469:Alkaline Phosphatase / Q000235:genetics; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D002467:Cell Nucleus / Q000201:enzymology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000201:enzymology*; D015870:Gene Expression; D006132:Growth Plate / Q000201:enzymology* / Q000254:growth & development; D006801:Humans; D051379:Mice; D010006:Osteoblasts / Q000201:enzymology*; D015675:Osteocalcin / Q000235:genetics; D010012:Osteogenesis; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D036122:Receptor, EphA4 / Q000235:genetics / Q000378:metabolism*
D034741:RNA, Small Interfering; D015675:Osteocalcin; D036122:Receptor, EphA4; D000469:Alkaline Phosphatase