A single-point mutation in FGFR2 affects cell cycle and Tgfβ signalling in osteoblasts

Genetic insights into the 'sandwich fusion' subtype of Klippel-Feil syndrome: novel FGFR2 mutations identified by 21 cases of whole-exome sequencing

BACKGROUND

Klippel-Feil syndrome (KFS) is a rare congenital disorder characterized by the fusion of two or more cervical vertebrae during early prenatal development. This fusion results from a failure of segmentation during the first trimester. Although six genes have previously been associated with KFS, they account for only a small proportion of cases. Among the distinct subtypes of KFS, "sandwich fusion" involving concurrent fusion of C0-1 and C2-3 vertebrae is particularly noteworthy due to its heightened risk for atlantoaxial dislocation. In this study, we aimed to investigate novel candidate mutations in patients with "sandwich fusion."

METHODS

We collected and analyzed clinical data from 21 patients diagnosed with "sandwich fusion." Whole-exome sequencing (WES) was performed, followed by rigorous bioinformatics analyses. Our focus was on the six known KFS-related genes (GDF3, GDF6, MEOX1, PAX1, RIPPLY2, and MYO18). Suspicious mutations were subsequently validated through in vitro experiments.

RESULTS

Our investigation revealed two novel exonic mutations in the FGFR2 gene, which had not previously been associated with KFS. Notably, the c.1750A > G variant in Exon 13 of FGFR2 was situated within the tyrosine kinase domain of the protein, in close proximity to several established post-translational modification sites. In vitro experiments demonstrated that this certain mutation significantly impacted the function of FGFR2. Furthermore, we identified four heterozygous candidate variants in two genes (PAX1 and MYO18B) in two patients, with three of these variants predicted to have potential clinical significance directly linked to KFS.

CONCLUSIONS

This study encompassed the largest cohort of patients with the unique "sandwich fusion" subtype of KFS and employed WES to explore candidate mutations associated with this condition. Our findings unveiled novel variants in PAX1, MYO18B, and FGFR2 as potential risk mutations specific to this subtype of KFS.

The efficacy of cisplatin on nasopharyngeal carcinoma cells may be increased via the downregulation of fibroblast growth factor receptor 2

Cisplatin is one of the primary compounds used in the treatment of nasopharyngeal carcinoma (NPC), and fibroblast growth factor receptor 2 (FGFR2) has emerged to be a promising target for treatment in various tumors. Therefore, the present study aimed to explore whether the expression levels of FGFR2 in NPC tissues and cell lines were altered, and whether the efficiency of cisplatin was increased following the downregulation of FGFR2. The downregulation of FGFR2 was achieved by transfection with a small interfering RNA against FGFR2. Tissues of patients with NPC were analyzed by immunohistochemistry. Cell viability was examined using a Cell Counting Kit‑8 assay. Cell cycle analysis was performed using flow cytometry. mRNA and protein levels were measured by reverse transcription quantitative polymerase chain reaction and western blot analysis, respectively. FGFR2 was observed to be overexpressed in cancer tissues of patients with NPC and in the NPC SUNE1, C666‑1, 6‑10B and HNE‑3 cell lines, and resulted in an unfavorable prognosis. Cisplatin treatment decreased cell viability and increased FGFR2 expression. The silencing of FGFR2 was demonstrated to augment the effects of cisplatin treatment, including decreasing the cell viability and inducing cell cycle arrest, which involved the increase and decrease of the durations of G1 and S phases, respectively, and a decrease in the expression levels of cyclin D1 and CDC25A, and increasing the rate of apoptosis via the intrinsic apoptosis pathway, as demonstrated by the upregulation of cleaved caspase‑3 and B‑cell lymphoma 2 (Bcl‑2)‑associated X protein and downregulation of Bcl‑2, in SUNE1 and C666‑1 cell lines. FGFR2 was overexpressed in the cancer tissues of patients with NPC and in NPC cell lines, resulting in an unfavorable prognosis. The downregulation of FGFR2 decreased cell viability via cell cycle arrest at G1 phase, and increased the efficacy of the cisplatin‑based induction of apoptosis through the intrinsic apoptosis pathway.

Effect of serum fibroblast growth factor receptor 2 and CAPS proteins on calcium status in β-thalassaemia major patients who are free from overt inflammation

Bone disorders and disturbed calcium (Ca) homeostasis are common disorders in β-thalassaemia major (β-TM). In the present study, two bone related markers are studied in β-TM patients with negative C-reactive protein for the first time; fibroblast growth factor receptor 2 (FGFR2) and CAPS protein. Another goal is to estimate the correlation between the recent parameters and bone biomaterials as a function of iron status parameters in β-TM patients. The results revealed that, in patients with β-TM serum FGFR2, CAPS, alkaline phosphatase (ALP) and Mg significantly increased while serum Ca levels were low as compared with controls. Ca status is correlated with iron overload in β-TM. A significant correlation was present between CAPS and FGFR2. In conclusion, FGFR2 and CAPS associated with Ca status and subsequent bone disturbances in β-TM patients. Their level can be predicted from the equation: CAPS =0.001ALP +0.48FGFR2-1.26Ca - 3.95Pi +12.76 with acceptable applicability.

FGFR2 regulation by picrasidine Q inhibits the cell growth and induces apoptosis in esophageal squamous cell carcinoma

Fibroblast growth factor receptor (FGFR) 2 and its downstream signaling cascades, PI3 K/AKT/mTOR is playing an important role in cell survival and proliferations. In this study, we firstly found that picrasidine Q (PQ), an alkaloid component extracted from Angelica keiskei species, has the capacity of anti-cell transformation and anti-cancer. After ligand shape similarity approach of PQ, we found that PQ targeted FGFR 2 and verified by FGFR2 kinase assay as well as computational docking model. FGFR2 highly expressed in esophageal cancer tissues and PQ inhibited fibroblast growth factor (FGF)-induced cell transformation. Furthermore, PQ inhibited cell proliferation and induced cell cycle arrest and apoptosis in KYSE30, KYSE410, and KYSE450 esophageal squamous cell carcinoma (ESCC) cells. It was confirmed by detecting of biological markers such as cyclinD1, cyclinD3 and cyclinB1 for cell cycle or cleaved caspase-7, caspase-3, and PARP for apoptosis. PQ targeting of FGFR2 kinase activities suppressed downstream target proteins including phosphorylation of AKT and mTOR but not MEK/ERK signaling pathways. Taken together, our results are the first to identify that PQ might be a chemopreventive and chemotherapeutic agent by direct targeting FGFR2 and inhibiting cell proliferation of ESCC cells.

Association analyses of FGFR2 gene polymorphisms with femoral neck bone mineral density in Chinese Han population

Femoral neck (FN) bone mineral density (BMD) is the most important risk phenotype for osteoporosis and has been used as a reference standard for describing osteoporosis. Identification of genetic variations associated with FN BMD may provide potential targets for therapeutic studies. Given the important biological role of FGFR2 gene involved in bone, we tested the associations between FGFR2 polymorphisms and FN BMD in 1,300 Chinese Han subjects. Of the 28 total SNPs, 2 SNPs, namely rs11200014 and rs1078806, were significantly associated with FN BMD under dominant model (P = 0.0014 and 0.0012, respectively) after conservative Bonferroni correction. The two SNPs were in complete linkage disequilibrium. In addition, haplotype-based association tests identified two haplotypes significantly associated with FN BMD, including one haplotype in block 4 where the two SNPs located. However, different from previous studies in white older men, we did not detect any significant association in sex-stratified analyses. In summary, our findings suggest that the FGFR2 gene may play an important role in variation in FN BMD in Chinese Han population, independent of gender effects. Further studies performed in multiple and large samples are needed to elucidate the underlying molecular mechanism and pathophysiology of osteoporosis.

Osteoprogenitor cell adhesiveness to a titanium mesh. A clinically relevant hypothesis for revision surgery in hip replacement

Bone defects are a major problem in primary and, even worse, revision surgery of the hip. Impacted allograft contained by a metallic mesh has been used for bone reconstruction. However, since allograft has been claimed to reabsorb, and to provoke immunogenic responses with potential viral infection and loosening because of allograft and mesh interface, new bone substitutes are being searched for. In this study we have cultured committed osteoprogenitor cells within a titanium mesh. The cells not only multiplied very easily, but also adhered to the mesh surface. We believe this phenomenon may have great clinical relevance for cell therapy as an alternative to allograft for the treatment of bone defects in acetabular or femoral reconstruction in revision surgery of the hip.

Modulation of calcium-induced cell death in human neural stem cells by the novel peptidylarginine deiminase-AIF pathway

PADs (peptidylarginine deiminases) are calcium-dependent enzymes that change protein-bound arginine to citrulline (citrullination/deimination) affecting protein conformation and function. PAD up-regulation following chick spinal cord injury has been linked to extensive tissue damage and loss of regenerative capability. Having found that human neural stem cells (hNSCs) expressed PAD2 and PAD3, we studied PAD function in these cells and investigated PAD3 as a potential target for neuroprotection by mimicking calcium-induced secondary injury responses. We show that PAD3, rather than PAD2 is a modulator of cell growth/death and that PAD activity is not associated with caspase-3-dependent cell death, but is required for AIF (apoptosis inducing factor)-mediated apoptosis. PAD inhibition prevents association of PAD3 with AIF and AIF cleavage required for its translocation to the nucleus. Finally, PAD inhibition also hinders calcium-induced cytoskeleton disassembly and association of PAD3 with vimentin, that we show to be associated also with AIF; together this suggests that PAD-dependent cytoskeleton disassembly may play a role in AIF translocation to the nucleus. This is the first study highlighting a role of PAD activity in balancing hNSC survival/death, identifying PAD3 as an important upstream regulator of calcium-induced apoptosis, which could be targeted to reduce neural loss, and shedding light on the mechanisms involved.

Monitoring ferumoxide-labelled neural progenitor cells and lesion evolution by magnetic resonance imaging in a model of cell transplantation in cerebral ischaemia

Efficacy of neural stem/progenitor cell (NPC) therapies after cerebral ischaemia could be better evaluated by monitoring in vivo migration and distribution of cells post-engraftment in parallel with analysis of lesion volume and functional recovery. Magnetic resonance imaging (MRI) is ideally placed to achieve this, but still poses several challenges. We show that combining the ferumoxide MRI contrast agent Endorem with protamine sulphate (FePro) improves iron oxide uptake in cells compared to Endorem alone and is non-toxic. Hence FePro complex is a better contrast agent than Endorem for monitoring NPCs. FePro complex-labelled NPCs proliferated and differentiated normally in vitro, and upon grafting into the brain 48 hours post-ischaemia they were detected in vivo by MRI. Imaging over four weeks showed the development of a confounding endogenous hypointense contrast evolution at later timepoints within the lesioned tissue. This was at least partly due to accumulation within the lesion of macrophages and endogenous iron. Neither significant NPC migration, assessed by MRI and histologically, nor a reduction in the ischaemic lesion volume was observed in NPC-grafted brains.  Crucially, while MRI provides reliable information on engrafted cell location early after an ischaemic insult, pathophysiological changes to ischaemic lesions can interfere with cellular imaging at later timepoints.

Effects of thyroxine exposure on osteogenesis in mouse calvarial pre-osteoblasts

The incidence of craniosynostosis is one in every 1,800–2500 births. The gene-environment model proposes that if a genetic predisposition is coupled with environmental exposures, the effects can be multiplicative resulting in severely abnormal phenotypes. At present, very little is known about the role of gene-environment interactions in modulating craniosynostosis phenotypes, but prior evidence suggests a role for endocrine factors. Here we provide a report of the effects of thyroid hormone exposure on murine calvaria cells. Murine derived calvaria cells were exposed to critical doses of pharmaceutical thyroxine and analyzed after 3 and 7 days of treatment. Endpoint assays were designed to determine the effects of the hormone exposure on markers of osteogenesis and included, proliferation assay, quantitative ALP activity assay, targeted qPCR for mRNA expression of Runx2, Alp, Ocn, and Twist1, genechip array for 28,853 targets, and targeted osteogenic microarray with qPCR confirmations. Exposure to thyroxine stimulated the cells to express ALP in a dose dependent manner. There were no patterns of difference observed for proliferation. Targeted RNA expression data confirmed expression increases for Alp and Ocn at 7 days in culture. The genechip array suggests substantive expression differences for 46 gene targets and the targeted osteogenesis microarray indicated 23 targets with substantive differences. 11 gene targets were chosen for qPCR confirmation because of their known association with bone or craniosynostosis (Col2a1, Dmp1, Fgf1, 2, Igf1, Mmp9, Phex, Tnf, Htra1, Por, and Dcn). We confirmed substantive increases in mRNA for Phex, FGF1, 2, Tnf, Dmp1, Htra1, Por, Igf1 and Mmp9, and substantive decreases for Dcn. It appears thyroid hormone may exert its effects through increasing osteogenesis. Targets isolated suggest a possible interaction for those gene products associated with calvarial suture growth and homeostasis as well as craniosynostosis.

Administration of growth factors for bone regeneration

Growth factors (GFs) such as BMPs, FGFs, VEGFs and IGFs have significant impacts on osteoblast behavior, and thus have been widely utilized for bone tissue regeneration. Recently, securing biological stability for a sustainable and controllable release to the target tissue has been a challenge to practical applications. This challenge has been addressed to some degree with the development of appropriate carrier materials and delivery systems. This review highlights the importance and roles of those GFs, as well as their proper administration for targeting bone regeneration. Additionally, the in vitro and in vivo performance of those GFs with or without the use of carrier systems in the repair and regeneration of bone tissue is systematically addressed. Moreover, some recent advances in the utility of the GFs, such as using fusion technology, are also reviewed.

Special AT-rich sequence-binding protein 2 and its related genes play key roles in the differentiation of MC3T3-E1 osteoblast like cells

Special AT-rich sequence-binding protein (SATB) plays a critical role in bone generation and osteoblast differentiation. In the present study, the differentially expressed genes by SATB2 overexpression were analyzed in MC3T3-E1 osteoblast-like cells using Alizarin red S staining, wound healing assay and Agilent's Human Oligo Microarray. Calcium mineralization and motility were significantly enhanced in SATB2-overexpressed cells compared with untreated control. In addition, using the GeneSpringGX 7.3 program to compare the identified genes expressed in SATB2-overexpresed cells with untreated control, we found several unique genes closely associated with osteoblast differentiation, including SOX2, MBP2, WNT11 and MEN1 (up-regulated genes), and ILK, FGF23, FGFR2, and SNAI1 (down-regulated genes). Consistent with microarray data, real-time RT-PCR confirmed the significant up- and down-regulation of these genes at mRNA level in SATB2-overexpressed MC3T3-E1 cells. Overall, our findings suggest that the molecular regulation of SATB2 can be an attractive approach to develop a novel therapeutic strategy for bone-related diseases.