Role of N-cadherin and protein kinase C in osteoblast gene activation induced by the S252W fibroblast growth factor receptor 2 mutation in apert craniosynostosis
J. Lemonnier et al., Role of N-cadherin and protein kinase C in osteoblast gene activation induced by the S252W fibroblast growth factor receptor 2 mutation in apert craniosynostosis, J BONE MIN, 16(5), 2001, pp. 832-845
Apert (Ap) syndrome is characterized by premature cranial suture ossificati
on caused by fibroblast growth factor receptor 2 (FGFR-2) mutations, We stu
died the role of cadherins and signaling events in the phenotypic alteratio
ns induced by the AD FGFR-2 S252W mutation in mutant immortalized fetal hum
an calvaria osteoblasts, The FGFR-2 mutation caused increased expression of
the osteoblast markers alkaline phosphatase (ALP), type 1 collagen (COLIA1
), and osteocalcin (OC) in long-term culture. The mutation also increased c
ell-cell aggregation, which was suppressed by specific neutralizing anti-N-
and anti-E-cadherin antibodies. Mutant osteoblasts showed increased N- and
E-cadherin, but not N-cell adhesion molecule (N-CAM) messenger RNA (mRNA)
and protein levels. This was confirmed in vivo by the abundant immunoreacti
ve N- and E-cadherins in preosteoblasts in the Ap suture whereas N-CAM and
alpha- and beta -catenins were unaffected. Neutralizing anti-N-cadherin ant
ibody or N-cadherin antisense (AS) oligonucleotides but not anti-E-cadherin
antibody or AS reduced ALP activity as well as ALP, COLIA1, and OC mRNA ov
erexpression in mutant osteoblasts. Analysis of signal transduction reveale
d increased phospholipase C gamma (PLC gamma) and protein kinase C alpha (P
LC alpha) phosphorylation and increased PKC activity in mutant cells in bas
al conditions. Inhibition of PKC by calphostin C or the PKC alpha -specific
inhibitor Go6976 suppressed the increased N-cadherin mRNA and protein leve
ls as well as the overexpression of ALP COLIA1, and OC mRNA in mutant cells
. Thus, N-cadherin plays a role in the activation of osteoblast differentia
tion marker genes in mutant osteoblasts and PKC alpha signaling appears to
be involved in the increased N-cadherin and osteoblast gene expression indu
ced by the S252W FGFR-2 mutation in human osteoblasts.