FGFR2 Mutation Confers a Less Drastic Gain of Function in Mesenchymal Stem Cells Than in Fibroblasts

Abstract

Gain-of-function mutations in FGFR2 cause Apert syndrome (AS), a disease characterized by craniosynostosis and limb bone defects both due to abnormalities in bone differentiation and remodeling. Although the periosteum is an important cell source for bone remodeling, its role in craniosynostosis remains poorly characterized. We hypothesized that periosteal mesenchymal stem cells (MSCs) and fibroblasts from AS patients have abnormal cell phenotypes that contribute to the recurrent fusion of the coronal sutures. MSCs and fibroblasts were obtained from the periostea of 3 AS patients (S252W) and 3 control individuals (WT). We evaluated the proliferation, migration, and osteogenic differentiation of these cells. Interestingly, S252W mutation had opposite effects on different cell types: S252W MSCs proliferated less than WT MSCs, while S252W fibroblasts proliferated more than WT fibroblasts. Under restrictive media conditions, only S252W fibroblasts showed enhanced migration. The presence of S252W mutation increased in vitro and in vivo osteogenic differentiation in both studied cell types, though the difference compared to WT cells was more pronounced in S252W fibroblasts. This osteogenic differentiation was reversed through inhibition of JNK. We demonstrated that S252W fibroblasts can induce osteogenic differentiation in periosteal MSCs but not in MSCs from another tissue. MSCs and fibroblasts responded differently to the pathogenic effects of the FGFR2S252W mutation. We propose that cells from the periosteum have a more important role in the premature fusion of cranial sutures than previously thought and that molecules in JNK pathway are strong candidates for the treatment of AS patients.Electronic supplementary materialThe online version of this article (doi:10.1007/s12015-011-9327-6) contains supplementary material, which is available to authorized users.

Fibroblast growth factor signaling in skeletal development and disease

“…At a later stage, activating FGFR2 mutations were widely found to cause increased osteoblast marker gene expression and accelerated osteoblast maturation in cranial sutures (Eswarakumar et al 2004;Yang et al 2008;Yin et al 2008;Holmes et al 2009;Yeh et al 2012;Liu et al 2013a,b;Morita et al 2014). This finding in mice supports the original observation in humans that Apert and Crouzon FGFR2 mutations cause increased osteoblast maturation and function in postnatal human suture development (Lomri et al 1998;Lemonnier et al 2001b;Tanimoto et al 2004;Baroni et al 2005;Marie 2015).…”

Novel Molecular Pathways Elicited by Mutant FGFR2 May Account for Brain Abnormalities in Apert Syndrome

“…Coronal suture periosteal fibroblasts from three unrelated AS patients, three unrelated CS patients and from three age- and sex-matched control subjects were obtained as previously described [9], [12]. The presence of the S252W and C342Y mutations were confirmed by direct DNA sequencing and expression of the mesenchyme-specific isoform of FGFR2 in the primary fibroblasts was examined by Western Blot and RT-PCR [9], [12].…”

The molecular and cellular basis of Apert syndrome

“…Apert fibroblasts treated with SP600125, a JNK phosphorylation inhibitor reduced its ALP activity and mineralization (30). S252W mutated FGFR2 enhanced EGFR and PDGFRα mRNA expression via activation of PKCα-dependent AP-1 transcriptional activity.…”

“…However, AS skull osteoblasts demonstrated a decreased growth rate compared with normal cells in vitro (29). Comparative analysis of the proliferation of wild-type (WT) (from 3 individuals) and mutated-type (MT) (from 3 AS patients) fibroblasts and mesenchymal stem cells showed increased cell growth in MT fibroblasts and decreased in MT MSCs (30).…”

“…Tanimoto et al compared differentiation of osteoblasts from the digital bone of two Apert patients with the FGFR2 S252W mutation and two independent non-syndromic polydactyly patients, and revealed that the Apert osteoblasts showed more prominent ALP, OC and osteopontin mRNA expression and mineralized nodule formation (35). In 2012, Yeh et al found both that the coronal suture periosteal fibroblasts and MSCs from three unrelated AS patients showed enhanced osteogenic differentiation compared to cells from age-and sexmatched control subjects in vivo and vitro (30).…”