Pathogenesis of Paget's disease of bone

Woven bone formation and mineralization by rat mesenchymal stromal cells imply increased expression of the intermediate filament desmin

Background

Disordered and hypomineralized woven bone formation by dysfunctional mesenchymal stromal cells (MSCs) characterize delayed fracture healing and endocrine -metabolic bone disorders like fibrous dysplasia and Paget disease of bone. To shed light on molecular players in osteoblast differentiation, woven bone formation, and mineralization by MSCs we looked at the intermediate filament desmin (DES) during the skeletogenic commitment of rat bone marrow MSCs (rBMSCs), where its bone-related action remains elusive.

Results

Monolayer cultures of immunophenotypically- and morphologically - characterized, adult male rBMSCs showed co-localization of desmin (DES) with vimentin, F-actin, and runx2 in all cell morphotypes, each contributing to sparse and dense colonies. Proteomic analysis of these cells revealed a topologically-relevant interactome, focused on cytoskeletal and related enzymes//chaperone/signalling molecules linking DES to runx2 and alkaline phosphatase (ALP). Osteogenic differentiation led to mineralized woven bone nodules confined to dense colonies, significantly smaller and more circular with respect to controls. It significantly increased also colony-forming efficiency and the number of DES-immunoreactive dense colonies, and immunostaining of co-localized DES/runx-2 and DES/ALP. These data confirmed pre-osteoblastic and osteoblastic differentiation, woven bone formation, and mineralization, supporting DES as a player in the molecular pathway leading to the osteogenic fate of rBMSCs.

Conclusion

Immunocytochemical and morphometric studies coupled with proteomic and bioinformatic analysis support the concept that DES may act as an upstream signal for the skeletogenic commitment of rBMSCs. Thus, we suggest that altered metabolism of osteoblasts, woven bone, and mineralization by dysfunctional BMSCs might early be revealed by changes in DES expression//levels. Non-union fractures and endocrine - metabolic bone disorders like fibrous dysplasia and Paget disease of bone might take advantage of this molecular evidence for their early diagnosis and follow-up.

The accuracy of quantifying the degree of hard tissue calcification using an electron probe micro analyzer, micro-focus X-ray computed tomography, and tissue sectioning methods

OBJECTIVES

Micro-focus X-ray computed tomography (μCT) helps evaluate specimens without destroying it. However, its accuracy of quantifying bone mineral density remains to be fully elucidated. We aimed to verify the accuracy of calcification assessed by μCT, by comparing the images of identical specimens obtained via different methods such as μCT and electron probe micro analyzer (EPMA) analyses.

METHODS

The maxillae, mandibles, and tibiae of five-week-old male mice were analyzed. Calcification density was analyzed using μCT. The right sides of the specimens were decalcified and processed for Azan staining. The left side of the specimens underwent elemental mapping for Ca, Mg, and P using EPMA.

RESULTS

μCT revealed a significant increase in calcification levels in the following order: enamel, dentin, cortical bone, and trabecular bone. These results reflected the Ca and P levels observed in the EPMA analyses. μCT demonstrated significant differences in the degree of calcification among the enamel tissues or dentin tissues, except for dentin in the maxillary incisors and molars. However, EPMA analysis did not demonstrate significant differences in the Ca and P levels among the same tissue samples.

CONCLUSIONS

EPMA elemental analysis can be used to measure Ca and P levels for evaluating the calcification rate of hard tissues. Additionally, the study results validate the evaluation of calcification density via μCT. Furthermore, μCT can evaluate even minute differences in calcification rates compared with EPMA analysis.

From Cells to Environment: Exploring the Interplay between Factors Shaping Bone Health and Disease

The skeletal system is an extraordinary structure that serves multiple purposes within the body, including providing support, facilitating movement, and safeguarding vital organs. Moreover, it acts as a reservoir for essential minerals crucial for overall bodily function. The intricate interplay of bone cells plays a critical role in maintaining bone homeostasis, ensuring a delicate balance. However, various factors, both intrinsic and extrinsic, can disrupt this vital physiological process. These factors encompass genetics, aging, dietary and lifestyle choices, the gut microbiome, environmental toxins, and more. They can interfere with bone health through several mechanisms, such as hormonal imbalances, disruptions in bone turnover, direct toxicity to osteoblasts, increased osteoclast activity, immune system aging, impaired inflammatory responses, and disturbances in the gut-bone axis. As a consequence, these disturbances can give rise to a range of bone disorders. The regulation of bone's physiological functions involves an intricate network of continuous processes known as bone remodeling, which is influenced by various intrinsic and extrinsic factors within the organism. However, our understanding of the precise cellular and molecular mechanisms governing the complex interactions between environmental factors and the host elements that affect bone health is still in its nascent stages. In light of this, this comprehensive review aims to explore emerging evidence surrounding bone homeostasis, potential risk factors influencing it, and prospective therapeutic interventions for future management of bone-related disorders.

The Ying and Yang of Sphingosine-1-Phosphate Signalling within the Bone

Bone remodelling is a highly active and dynamic process that involves the tight regulation of osteoblasts, osteoclasts, and their progenitors to allow for a balance of bone resorption and formation to be maintained. Ageing and inflammation are risk factors for the dysregulation of bone remodelling. Once the balance between bone formation and resorption is lost, bone mass becomes compromised, resulting in disorders such as osteoporosis and Paget's disease. Key molecules in the sphingosine-1-phosphate signalling pathway have been identified for their role in regulating bone remodelling, in addition to its more recognised role in inflammatory responses. This review discusses the accumulating evidence for the different, and, in certain circumstances, opposing, roles of S1P in bone homeostasis and disease, including osteoporosis, Paget's disease, and inflammatory bone loss. Specifically, we describe the current, often conflicting, evidence surrounding S1P function in osteoblasts, osteoclasts, and their precursors in health and disease, concluding that S1P may be an effective biomarker of bone disease and also an attractive therapeutic target for disease.

Management of Massive Mandibular Fibrous Dysplasia with Radical Excision and Different Immediate Reconstructive Modalities: Case Series Report

Purpose

To review and represent three different mandibular reconstruction modalities following surgical treatment of massive mandibular fibrous Dysplasia (MMFD).

Methods

The present retrospective case series study was conducted on 24 patients who had MMFD and treated via resection and immediate reconstruction at Al-Azhar University Hospitals, Egypt. Patients were divided into three groups according to the grafting procedure. Group I patients were grafted with iliac bone graft (IBG), group II patients were grafted with IBG and bone marrow aspirate concentrate (BMAC), while group III patients were grafted with free vascularized fibula graft (FVFG). Postoperative clinical and radiographic assessments were performed immediately, at 6 months, 12 months and 2 years to evaluate lesion recurrence and bone graft resorption. Other study variables included assessment of postoperative wound dehiscence, infection rate, amount of edema, and facial bone contour.

Results

The parameters of the clinical analysis showed non-statistically significant differences among all groups. Postoperative wound healing was clinically uneventful in all groups, except for two cases of wound dehiscence in group I (8.3%) and one case in group III (4.2%). Most patients had appropriate postoperative facial contour, and adequate facial symmetry. The radiographic measurements revealed a highly statistically significant difference between group I and II at 12 months, and two years, without any statistically significant difference between group II and III.

Conclusion

MMFD surgical defect should be repaired for function and cosmetics aims especially in young adult patients. The findings of the present study have shown that when compared to traditional IBG alone or FVFG, the use of autogenous IBG with BMAC injection produces a favorable outcome with few difficulties.

Epigenetic DNA Methylation Signatures Associated With the Severity of Paget's Disease of Bone

Background: Paget's disease of bone (PDB) is characterized by focal areas of dysregulated bone turnover resulting in increased bone loss and abnormal bone formation with variable severity. PDB has a complex etiology and both genetics and environmental factors have been implicated. A recent study has identified many differentially methylated loci in PDB compared to healthy subjects. However, associations between DNA methylation profiles and disease severity of PDB have not been investigated. Objectives: To investigate the association between DNA methylation signals and PDB severity. Methods: Using 232 well-characterized PDB subjects from the PRISM trial, a disease severity score was devised based on the clinical features of PDB. DNA methylation profiling was performed using Illumina Infinium HumanMethylation 450K array. Results: We identified 100 CpG methylation sites significantly associated with PDB severity at FDR <0.05. Additionally, methylation profiles in 11 regions showed Bonferroni-significant association with disease severity including six islands (located in VCL, TBX5, CASZ1, ULBP2, NUDT15 and SQSTM1), two gene bodies (CXCR6 and DENND1A), and 3 promoter regions (RPL27, LINC00301 and VPS29). Moreover, FDR-significant effects from region analysis implicated genes with genetic variants previously associated with PDB severity, including RIN3 and CSF1. A multivariate predictor model featuring the top severity-associated CpG sites revealed a significant correlation (R = 0.71, p = 6.9 × 10-16) between observed and predicted PDB severity scores. On dichotomizing the severity scores into low and high severity, the model featured an area under curve (AUC) of 0.80, a sensitivity of 0.74 and a specificity of 0.68. Conclusion: We identified several CpG methylation markers that are associated with PDB severity in this pioneering study while also highlighting the novel molecular pathways associated with disease progression. Further work is warranted to affirm the suitability of our model to predict the severity of PDB in newly diagnosed patients or patients with family history of PDB.

Total Hip Replacements in Patients with Rare Pathologic Conditions Affecting Bone

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As a result of the advances in surgical technique and implant design, total hip arthroplasty (THA) is increasingly offered for the management of osteoarthritis of the hip in patients with fragile or pathologic bone.

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Posttraumatic or congenital deformities associated with fragile or pathologic bone are frequently encountered and necessitate diligent preoperative planning.

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Surgeons should be prepared to evaluate and manage intraoperative iatrogenic fracture.

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While there is limited evidence to date, components made with computer-assisted design can be considered, given the unique and highly variable patient population.

Molecular modelling and dynamic simulations of sequestosome 1 (SQSTM1) missense mutations linked to Paget disease of bone

The Paget disease (PDB; OMIM is 167250) is a chronic bone disease caused by pathogenic mutations in Sequestome1/p62 (SQSTM1) gene. This study has aimed to interpret the relationship of PDB linked SQSTM1 mutations with protein structure and its molecular dynamic features. The disease causative missense mutations were initially collected, and then analyzed for their, exonic and domain distribution, impact on secondary and tertiary structures, and their ability on protein-ligand interactions, using a combination of systems biology approaches. Our results show that most PDB linked SQSTM1 missense mutations affect amino acid residues clustered within or near the UBA domain (aa 389-434), which participates in the ubiquitination of substrates. We also report that the majority mutations occurred in α-helices over β-strands but their effects on the secondary structure were mostly neutral. Global tertiary structure deviations were minimal; however, at amino acid residue level minor structural changes were evident. The molecular dynamics simulation analysis showed that both PB1 and UBA domains were under constant structural fluctuations resulting in closed form conformation of SQSMT1 protein structure, when it is bound to PRKCI ligand. We also found salt bridge conformation changes in the UBA domain of SQSTM1 mutants when they bound to the PRKCI interactor protein. This finding suggests the possibility that mutations in SQSTM1 could impair its ability to ubiquitinate the substrates, eventually affecting autophagy and apoptosis, especially in mature osteoclasts. This study presents the additional insight into structure and function relationship between SQSTM1 mutations and PDB pathogenesis. Communicated by Ramaswamy H. Sarma.

Cervical scoliosis and torticollis: a novel skeletal anomaly in broiler chickens

Background

Among the most prominent health problems marring the global poultry industry for several decades are skeletal abnormalities. The aim of this study was to investigate a recent emergence of a novel form of skeletal deformity affecting cervical spine in broiler chickens. This work presents the natural history of this newly emerging skeletal anomaly along with long term observations of epidemiological trends in commercial broiler flocks, and clinical and pathological features.

Results

In distinction from other forms of skeletal deformities commonly reported in broiler chickens, this new form of cervical spine anomaly have been observed in newly hatched chicks and in fully developed embryos that died in the shell. On clinical and post mortem examination this condition presents characteristic features consistent with congenital cervical scoliosis and torticollis (CCST). The pathogenesis of CCST appears to be linked to pathological remodeling of the cervical vertebrae bone associated with excessive activity of osteoclasts. Long term observations indicate that the incidence of CCST showed increasing epidemiological trends over time. More recently CCST has been observed in newly hatched chicks with incidence ranging from 0.1 to > 1%, and in fully developed embryos that failed to hatch about 4 to 5%.

Conclusions

The increasing trends in incidence of CCST in commercial broiler flocks are of concern from an economic perspective, and also represent a very specific and important aspect of animal welfare.

Evaluation of Bone Metabolism Biomarkers in Paget's Disease of Bone

Objective: To evaluate serum levels of bone metabolism biomarkers in patients with Paget's disease of bone (PDB).

Methods: Serum levels of osteopontin, sclerostin, receptor activator of nuclear factor kappa-Β ligand (RANKL), osteoprotegerin, Dickkopf-related protein 1 (DKK-1), and soluble frizzled-related protein 1 (sFRP-1) were measured in 57 patients with Paget’s disease of bone and 24 controls with primary osteoarthritis. Subgroup analysis was employed to identify any differences in bone metabolism biomarker levels according to disease activity or current treatment.

Results: Patients with PDB presented higher levels of osteopontin and RANKL. When compared with patients with inactive disease, patients with active disease presented higher levels of bone-specific alkaline phosphatase (BAP) and osteopontin. There was a significant correlation between serum levels of BAP and osteopontin. There was no significant correlation between levels of BAP and other bone metabolism biomarkers. Current disease extension on bone scintigraphy had a significant correlation with serum levels of osteopontin and BAP. There was no significant correlation between current disease extension and other bone metabolism biomarkers. Serum levels of osteopontin and RANKL were correlated to serum levels of BAP and disease extension.

Conclusion: Patients with PDB presented higher levels of osteopontin and RANKL. Osteopontin could be a useful biomarker for activity and extension of PDB.

VCP/p97 increases BMP signaling by accelerating ubiquitin ligase Smurf1 degradation

The bone morphogenetic protein (BMP)-Smad signaling pathway plays a crucial role in the control of bone homeostasis by regulating osteoblast activity. It is known that the ubiquitin ligase Smad ubiquitination regulatory factor (Smurf)1 is a master negative regulator of BMP signaling, but how its stability and activity are regulated remains poorly understood. Our study showed that valosin-containing protein/p97, the mutations of which lead to rare forms of Paget's disease of bone (PDB)-like syndrome-such as inclusion body myopathy (IBM) associated with Paget's disease of bone and frontotemporal dementia (IBM-PFD)-together with its adaptor nuclear protein localization (NPL)4, specifically interact with Smurf1 and deliver the ubiquitinated Smurf1 for degradation. Depletion of either p97 or NPL4 resulted in the elevation of Smurf1 protein level and decreased BMP signaling accordingly. Mechanically, a typical proline, glutamic acid, serine, and threonine motif specifically existing in Smurf1 is necessary for its recognition and degradation by p97, and this process is dependent on p97 ATPase activity. More importantly, compared with p97 WT, PDB-associated mutation of p97 (mainly A232E) harboring the higher ATPase activity of p97 further promoted Smurf1 degradation, thus increasing BMP signaling activity. Our findings first establish a link between p97 and Smurf1, providing an in-depth understanding of how Smurf1 is regulated, as well as the mechanism of p97-related bone diseases.-Li, H., Cui, Y., Wei, J., Liu, C., Chen, Y., Cui, C.-P., Li, L., Zhang, X., Zhang, L. VCP/p97 increases BMP signaling by accelerating ubiquitin ligase Smurf1 degradation.

Adult Paget's disease of bone: a review

Adult PD of bone is the second commonest metabolic bone condition after osteoporosis. The condition is characterized by increased bone cell activity, with bone-resorbing osteoclasts often larger and containing more nuclei than normal, and osteoblasts producing increased amounts of disorganized bone. This leads to expanded bone of poor quality possessing both sclerotic and lytic areas. PD of bone has a strong genetic element, with a family history being noted in 10-20% of cases. A number of genetic defects have been found to be associated with the condition. The most common disease-associated variants identified affect the SQSTM1 gene, providing insights into disease aetiology, with the clinical value of knowledge of SQSTM1 mutation status currently under active investigation. The diagnosis may be suggested by an isolated raised total ALP without other identifiable causes. This can be confirmed on plain X-rays and the extent determined by isotope bone scan. The mainstays of treatment are the bisphosphonates, especially i.v. zoledronate, which results in long-term suppression of bone turnover. ALP is the usual means of monitoring the condition, although more specific bone turnover markers can be helpful, especially in coincident liver disease. Patients should be followed up to monitor for biochemical relapse or development of complications, which may require medical or surgical intervention.

Determinants of quality of life in Paget's disease of bone

OBJECTIVE

To evaluate the parameters associated with quality of life in patients with Paget's disease of bone.

METHODS

Patients with Paget's disease of bone were evaluated with SF-36 and WHOQOL-bref questionnaires. Patients with other diseases that could cause significant impairment of their quality of life were excluded. We searched for correlations between the results and: age, time from diagnosis, type of involvement, pain related to Paget's disease of bone, limitation to daily activities, deformities, bone specific alkaline phosphatase, the extent of involvement and treatment.

RESULTS

Fifty patients were included. Results of the SF-36 total score and its domains, physical and mental health, were significantly correlated with bone pain and deformities. Marital status was significantly correlated with the SF-36 total score and Mental Health Domain. BAP levels and disease extension were significantly correlated to SF-36 Physical Health Domain. After multivariate analysis, the only parameters that remained significantly associated with the SF-36 total score and to its Mental Health and Physical Health Domains were pain and marital status. The WHOQOL-bref total score was significantly associated with pain, physical impairment and deformities. WHOQOL-bref Domain 1 (physical) score was significantly associated with marital status, pain and deformities, while Domain 2 (psychological) score was associated with marital status, physical impairment and kind of involvement. After multivariate analysis, the presence of pain, deformities, and marital status were significantly associated with results of the WHOQOL-bref total score and its Domain 1. WHOQOL-bref domain 2 results were significantly predicted by pain and marital status.

CONCLUSION

The main disease-related factor associated with SF-36 results in Paget's disease of bone patients was bone pain, while bone pain and deformities were associated with WHOQOL-bref.

Myogenic differentiation of VCP disease-induced pluripotent stem cells: A novel platform for drug discovery

Valosin Containing Protein (VCP) disease is an autosomal dominant multisystem proteinopathy caused by mutations in the VCP gene, and is primarily associated with progressive muscle weakness, including atrophy of the pelvic and shoulder girdle muscles. Currently, no treatments are available and cardiac and respiratory failures can lead to mortality at an early age. VCP is an AAA ATPase multifunction complex protein and mutations in the VCP gene resulting in disrupted autophagic clearance. Due to the rarity of the disease, the myopathic nature of the disorder, ethical and practical considerations, VCP disease muscle biopsies are difficult to obtain. Thus, disease-specific human induced pluripotent stem cells (hiPSCs) now provide a valuable resource for the research owing to their renewable and pluripotent nature. In the present study, we report the differentiation and characterization of a VCP disease-specific hiPSCs into precursors expressing myogenic markers including desmin, myogenic factor 5 (MYF5), myosin and heavy chain 2 (MYH2). VCP disease phenotype is characterized by high expression of TAR DNA Binding Protein-43 (TDP-43), ubiquitin (Ub), Light Chain 3-I/II protein (LC3-I/II), and p62/SQSTM1 (p62) protein indicating disruption of the autophagy cascade. Treatment of hiPSC precursors with autophagy stimulators Rapamycin, Perifosine, or AT101 showed reduction in VCP pathology markers TDP-43, LC3-I/II and p62/SQSTM1. Conversely, autophagy inhibitors chloroquine had no beneficial effect, and Spautin-1 or MHY1485 had modest effects. Our results illustrate that hiPSC technology provide a useful platform for a rapid drug discovery and hence constitutes a bridge between clinical and bench research in VCP and related diseases.

A FKBP5 mutation is associated with Paget's disease of bone and enhances osteoclastogenesis

Paget's disease of bone (PDB) is a common metabolic bone disease that is characterized by aberrant focal bone remodeling, which is caused by excessive osteoclastic bone resorption followed by disorganized osteoblastic bone formation. Genetic factors are a critical determinant of PDB pathogenesis, and several susceptibility genes and loci have been reported, including SQSTM1, TNFSF11A, TNFRSF11B, VCP, OPTN, CSF1 and DCSTAMP. Herein, we report a case of Chinese familial PDB without mutations in known genes and identify a novel c.163G>C (p.Val55Leu) mutation in FKBP5 (encodes FK506-binding protein 51, FKBP51) associated with PDB using whole-exome sequencing. Mutant FKBP51 enhanced the Akt phosphorylation and kinase activity in cells. A study of osteoclast function using FKBP51^V55L KI transgenic mice proved that osteoclast precursors from FKBP51^V55L mice were hyperresponsive to RANKL, and osteoclasts derived from FKBP51^V55L mice displayed more intensive bone resorbing activity than did FKBP51^WT controls. The osteoclast-specific molecules tartrate-resistant acid phosphatase, osteoclast-associated receptor and transcription factor NFATC1 were increased in bone marrow-derived monocyte/macrophage cells (BMMs) from FKBP51^V55L mice during osteoclast differentiation. However, c-fos expression showed no significant difference in the wild-type and mutant groups. Akt phosphorylation in FKBP51^V55L BMMs was elevated in response to RANKL. In contrast, IκB degradation, ERK phosphorylation and LC3II expression showed no difference in wild-type and mutant BMMs. Micro-CT analysis revealed an intensive trabecular bone resorption pattern in FKBP51^V55L mice, and suspicious osteolytic bone lesions were noted in three-dimensional reconstruction of distal femurs from mutant mice. These results demonstrate that the mutant FKBP51^V55L promotes osteoclastogenesis and function, which could subsequently participate in PDB development.

A method for whole protein isolation from human cranial bone

The presence of the dense hydroxyapatite matrix within human bone limits the applicability of conventional protocols for protein extraction. This has hindered the complete and accurate characterization of the human bone proteome thus far, leaving many bone-related disorders poorly understood. We sought to refine an existing method of protein extraction from mouse bone to extract whole proteins of varying molecular weights from human cranial bone. Whole protein was extracted from human cranial suture by mechanically processing samples using a method that limits protein degradation by minimizing heat introduction to proteins. The presence of whole protein was confirmed by western blotting. Mass spectrometry was used to sequence peptides and identify isolated proteins. The data have been deposited to the ProteomeXchange with identifier PXD003215. Extracted proteins were characterized as both intra- and extracellular and had molecular weights ranging from 9.4 to 629 kDa. High correlation scores among suture protein spectral counts support the reproducibility of the method. Ontology analytics revealed proteins of myriad functions including mediators of metabolic processes and cell organelles. These results demonstrate a reproducible method for isolation of whole protein from human cranial bone, representing a large range of molecular weights, origins and functions.

Milk-Derived Nanoparticle Fraction Promotes the Formation of Small Osteoclasts But Reduces Bone Resorption

The general consensus is that milk promotes bone growth and density because is a source of calcium and contains components that enhance intestinal calcium uptake or directly affect bone metabolism. In this study, we investigated the effect of bovine-derived milk 100,000 g pellet (P100), which contains nanoparticles (<220 nm) including extracellular vesicles, on osteoclast differentiation and bone resorption. Bone marrow-derived osteoclast precursor cells were differentiated into osteoclasts by M-CSF and RANKL (control) and in the presence of milk P100. Milk P100 treatment until day 4 increased the number of TRAP-positive mononuclear cells and small (≤5 nuclei) osteoclasts. The number of large (≥6 nuclei) osteoclasts remained the same. These alterations were associated with increased expression of TRAP, NFATc1, and c-Fos. Cells seeded in a calcium-phosphate coated plate or bone slices showed reduced resorption area when exposed to milk P100 during the differentiation phase and even after osteoclast formation. Interestingly, milk P100 treatment enhanced Cathepsin K expression but reduced Carbonic Anhydrase 2 gene expression. Moreover, intracellular acid production was also decreased by milk P100 treatment. Oral delivery of milk P100 to female DBA1/J mice for 7 weeks did not alter bone area; however, increased osteoclast number and area in tibia without changes in serum RANKL and CTX-I levels. We showed for the first time the effect of milk P100 on osteoclast differentiation both in vitro and in vivo and found that milk P100 increased the formation of small osteoclasts but this does not lead to more bone resorption probably due to reduced acid secretion. J. Cell. Physiol. 232: 225-233, 2017. © 2016 Wiley Periodicals, Inc.

VAV3 Gene Polymorphism Is Associated with Paget's Disease of Bone

BACKGROUND AND AIMS

Paget's disease of bone (PDB) is a focal bone disorder affecting the skeleton segmentally. The disease affects osteoclasts which increase in size, number, and activity. One of the etiopathogenic hypotheses is that the disease is genetic. It has been reported that Rho GEF Vav3 is an essential factor in the regulation of osteoclast function, and alteration of the VAV3 gene could influence the development of the disease. The aim of our study was to perform an association study between variants of the VAV3 gene and the risk of developing Paget's disease of bone.

PATIENTS AND METHODS

The genotypic and allelic distribution of the VAV3 c.892A>T/p.T298S (rs7528153) polymorphism was compared between a cohort of 238 Spanish subjects with PDB and a cohort of 253 healthy subjects.

RESULTS

Our results indicated that individuals carrying the VAV3 rs7528153 TT genotype were at a significantly increased risk of developing PDB (p < 0.001, odds ratio [OR] = 3.15, 95% confidence interval [95% CI] = 1.77-5.61).

CONCLUSIONS

These results suggest that inheriting the VAV3 rs7528153 polymorphism is a likely susceptibility factor for developing Paget's disease of bone.

Paget's sarcoma of the patella

Paget's sarcoma is a rare complication of Paget's disease and isolated Paget's disease of the patella is extremely rare. We describe a unique case of Paget's sarcoma of the patella in a 69-year-old male farmer who had a remote history of a fracture in the same patella 40 years previously. In this case, imaging and pathogenesis of Paget's disease of bone is described and factors implicated in the development of Paget's disease in this patient are evaluated.

Global gene expression profiling in R155H knock-in murine model of VCP disease

Dominant mutations in the valosin-containing protein (VCP) gene cause inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia, which is characterized by progressive muscle weakness, dysfunction in bone remodeling, and frontotemporal dementia. More recently, VCP has been linked to 2% of familial amyotrophic lateral sclerosis cases. VCP plays a significant role in a plethora of cellular functions including membrane fusion, transcription activation, nuclear envelope reconstruction, postmitotic organelle reassembly, and cell cycle control. To elucidate the pathological mechanisms underlying the VCP disease progression, we have previously generated a VCP(R155H/+) mouse model with the R155H mutation. Histological analyses of mutant muscle showed vacuolization of myofibrils, centrally located nuclei, and disorganized muscle fibers. Global expression profiling of VCP(R155H/+) mice using gene annotations by DAVID identified key dysregulated signaling pathways including genes involved in the physiological system development and function, diseases and disorders, and molecular and cellular functions. There were a total of 212 significantly dysregulated genes, several of which are involved in the regulation of proteasomal function and NF-κB signaling cascade. Findings of the gene expression study were validated by using quantitative reverse transcriptase polymerase chain reaction analyses to test genes involved in various signaling cascades. This investigation reveals the importance of the VCP(R155H/+) mouse model in the understanding of cellular and molecular mechanisms causing VCP-associated neurodegenerative diseases and in the discovery of novel therapeutic advancements and strategies for patients suffering with these debilitating disorders.

Paget sarcoma of the pelvic bone with widespread metastatic disease on radiography, CT, MRI, and 18F-FDG PET/CT with pathologic correlation

We report a case of Paget sarcoma of the left superior pubic ramus and disseminated metastatic disease in a 70-year-old man. Paget disease of the left hemipelvis with malignant degeneration in the region of the left superior pubic ramus was initially diagnosed on radiographs. Subsequent CT, MRI, PET/CT imaging, and CT-guided biopsy confirmed the diagnosis and showed extensive left-sided pelvic and abdominal lymphadenopathy with widespread metastatic disease to liver, spleen, and lungs.

Exclusion of TNFRSF11B as Candidate Gene for Otosclerosis in Campania Population

The etiology of otosclerosis is unknown. The etiopathogenesis of otosclerosis seems similar to that occurring in Paget's disease of bone, for which mutations or polymorphisms in several genes have been identified. Among these, TNFRSF11B gene encoding the osteoprotegerin is produced at high levels in the normal inner ear and at low level in active otosclerotic stapes footplates. The aim of this work was to verify the presence of a correlation between the rs2073618 (N3K) polymorphism in the TNFRSF11B gene and otosclerosis. Mutational screening in the TNFRSF11B gene was performed by direct sequencing. SNPs analysis was performed by PCR and by specific restriction enzyme assay with HpaI. The significance of the association was analyzed by statistical specific software. No causative mutation has been identified but the data suggested a strong correlation between the rs2073618 (N3K) polymorphism and otosclerosis. This correlation, however, has been excluded in a case-control study. This study excluded the association between the N3K polymorphism and otosclerosis in Campania region population.

Paget's disease of bone

Paget's disease is an osteoclastic-mediated disorder of bone that results in abnormal bone resorption associated with inadequate remodeling that leads to mechanically weakened bone. Demonstrating variable geographic prevalence, it is becoming less frequent and age of onset is lengthening in areas of once high prevalence prior to the institution of effective medical therapies, suggesting its etiology involves both environmental as well as genetic factors. Insights into its pathophysiology are helping to clarify other inherited osteolytic disorders of bone by providing additional insights into related cellular processes.

Paget disease of bone in Japanese patients: a report of three cases

Paget disease of bone (PDB) is a bone metabolic disorder causing pain, fractures, and deformity. Its incidence is estimated to be 1 to 2% in Caucasians older than 55 years, but in Asian populations the incidence is rare. We report on 2 female and one male Japanese patients aged 46 to 73 years with PDB. One patient had monostotic disease with pain around the shoulder and the other 2 were asymptomatic. All patients had elevated alkaline phosphatase (ALP) levels (range, 629-957 U/L). Two patients responded to oral bisphosphonate treatment and achieved normalised ALP levels and pain relief. One patient with polyostotic disease did not show any change in ALP levels. The diagnosis of the disease and the indications for bisphosphonate treatment are discussed.

Enhanced differentiation of osteoclasts from mononuclear precursors in patients with Gaucher disease

Gaucher disease (GD) is an autosomal recessive disorder caused by deficiency of β-glucocerebrosidase. Storage of glucosylceramide in reticuloendothelial cells results in multiorgan pathology including bone disease. Established skeletal disease may remain problematic despite Gaucher-specific treatment. Both osteopenia and osteonecrosis have been described but the underlying pathophysiology, in particular the role of monocyte-derived osteoclasts is not well defined. The objective of this study was to explore the effect of glucocerebrosidase deficiency, inhibition and replacement on osteoclast development and function. In cultures derived from GD patients, or where GBA was chemically inhibited multinucleate giant cells expressing markers of osteoclast differentiation occurred earlier and in greater numbers compared to normal controls and the functional capacity of osteoclasts for bone resorption was enhanced. Increases in osteoclast number and activity correlated with radiological markers of active bone disease. Abnormalities were reversed by addition of specific therapies and were attenuated by co-culture with cells derived from healthy controls (HCs). Numbers of osteoblast lineage cells in the peripheral blood were mismatched to osteoclast precursors indicating uncoupling of osteoblast-osteoclast regulation which may further impact on bone remodelling. Elucidation of the underlying mechanisms of these changes will suggest rational therapies for the most disabling aspect of this condition.

Genotype-phenotype studies of VCP-associated inclusion body myopathy with Paget disease of bone and/or frontotemporal dementia

Valosin containing protein (VCP) disease associated with inclusion body myopathy, Paget disease of the bone and frontotemporal dementia is a progressive autosomal dominant disorder caused by mutations in Valosin containing protein gene. To establish genotype-phenotype correlations we analyzed clinical and biochemical markers from a database of 190 members in 27 families harboring 10 missense mutations. Individuals were grouped into three categories: symptomatic, presymptomatic carriers and noncarriers. The symptomatic families were further divided into ten groups based on their VCP mutations. There was marked intra and inter-familial variation; and significant genotype-phenotype correlations were difficult to establish because of small numbers. Nevertheless when comparing the two most common mutations, R155C mutation was found to be more severe, with an earlier onset of myopathy and Paget (p = 0.03). Survival analysis of all subjects revealed an average life span after diagnosis of myopathy and Paget of 18 and 19 years respectively, and after dementia only 6 years. R155C had a reduced survival compared to the R155H mutation (p = 0.03).We identified amyotrophic lateral sclerosis (ALS) was diagnosed in 13 individuals (8.9%) and Parkinson's disease in five individuals (3%); however, there was no genotypic correlation. This study represents the largest dataset of patients with VCP disease and expands our understanding of the natural history and provides genotype-phenotype correlations in this unique disease.

Paget's Disease of Bone: A Review of Epidemiology, Pathophysiology and Management

Paget's disease of bone is a common disorder which may affect one or many bones. Although many patients are asymptomatic, a variety of symptoms and complications may occur. Fortunately, effective pharmacologic therapy, primarily with potent bisphosphonates, is now available to treat patients with complications or symptoms. This review of Paget's disease of bone will include epidemiology and pathophysiology, complications and clinical findings, indications for treatment, and the drugs currently available to treat this condition.

Pathogenesis of Paget disease of bone

Paget disease of bone (PDB) is a common disease characterized by focal areas of increased and disorganized bone turnover. Some patients are asymptomatic, whereas others develop complications such as pain, osteoarthritis, fracture, deformity, deafness, and nerve compression syndromes. PDB is primarily caused by dysregulation of osteoclast differentiation and function, and there is increasing evidence that this is due, in part, to genetic factors. One of the most important predisposing genes is SQSTM1, which harbors mutations that cause osteoclast activation in 5-20 % of PDB patients. Seven additional susceptibility loci for PDB have been identified by genomewide association studies on chromosomes 1p13, 7q33, 8q22, 10p13, 14q32, 15q24, and 18q21. Although the causal variants remain to be discovered, three of these loci contain CSF1, TNFRSF11A, and TM7SF4, genes that are known to play a critical role in osteoclast differentiation and function. Environmental factors are also important in the pathogenesis of PDB, as reflected by the fact that in many countries the disease has become less common and less severe over recent years. The most widely studied environmental trigger is paramyxovirus infection, but attempts to detect viral transcripts in tissues from patients with PDB have yielded mixed results. Although our understanding of the pathophysiology of PDB has advanced tremendously over the past 10 years, many questions remain unanswered, such as the mechanisms responsible for the focal nature of the disease and the recent changes in prevalence and severity.

Toward an integrative view of Optineurin functions

This review highlights recent advances in our understanding of the mechanisms of Optineurin (Optn) action and its implication in diseases. Optn has emerged as a key player regulating various physiological processes, including membrane trafficking, protein secretion, cell division and host defense against pathogens. Furthermore, there is growing evidence for an association of Optn mutations with human diseases such as primary open-angle glaucoma, amyotrophic lateral sclerosis and Paget's disease of bone. Optn functions depend on its precise subcellular localization and its interaction with other proteins. Here, we review the mechanisms that allow Optn to ensure a timely and spatially coordinated integration of different physiological processes and discuss how their deregulation may lead to different pathologies.

Proteomic analysis of a drosophila IBMPFD model reveals potential pathogenic mechanisms

IBMPFD, Inclusion body myopathy associated with Paget's disease of bone and frontotemporal dementia, is a hereditary degenerative disorder due to single missense mutations in VCP (Valosin-Containing Protein). The mechanisms of how mutations of VCP lead to IBMPFD remain mysterious. Here we utilize two-dimensional difference gel electrophoresis (2D-DIGE) combined with mass spectrometry to study the IBMPFD disorder at the protein level. With this set-up, we are able to employ comparative proteomics to analyze IBMPFD disease using Drosophila melanogaster as our disease model organism. Head proteome of transgenic D. melanogaster expressing wild type VCP is compared, respectively, with the head proteome of transgenic mutant type VCPs that correspond to human IBMPFD disease alleles (TER94(A229E), TER94(R188Q), and TER94(R152H)). Of all the proteins identified, a significant fraction of proteins altered in TER94(A229E) and TER94(R188Q) mutants belong to the same functional categories, i.e. apoptosis and metabolism. Among these, Drosophila transferrin is observed to be significantly up-regulated in mutant flies expressing TER94(A229E). A knock-down experiment suggests that fly transferrin might be a potential modifier in IBMPFD disease. The molecular analysis of IBMPFD disease may benefit from the proteomics approach which combines the advantages of high throughput analysis and the focus on protein levels.

From neurodevelopment to neurodegeneration: the interaction of neurofibromin and valosin-containing protein/p97 in regulation of dendritic spine formation

Both Neurofibromatosis type I (NF1) and inclusion body myopathy with Paget's disease of bone and frontotemporal dementia (IBMPFD) are autosomal dominant genetic disorders. These two diseases are fully penetrant but with high heterogeneity in phenotypes, suggesting the involvement of genetic modifiers in modulating patients' phenotypes. Although NF1 is recognized as a developmental disorder and IBMPFD is associated with degeneration of multiple tissues, a recent study discovered the direct protein interaction between neurofibromin, the protein product of the NF1 gene, and VCP/p97, encoded by the causative gene of IBMPFD. Both NF1 and VCP/p97 are critical for dendritic spine formation, which provides the cellular mechanism explaining the cognitive deficits and dementia found in patients. Moreover, disruption of the interaction between neurofibromin and VCP impairs dendritic spinogenesis. Neurofibromin likely influences multiple downstream pathways to control dendritic spinogenesis. One is to activate the protein kinase A pathway to initiate dendritic spine formation; another is to regulate the synaptic distribution of VCP and control the activity of VCP in dendritic spinogenesis. Since neurofibromin and VCP/p97 also regulate cell growth and bone metabolism, the understanding of neurofibromin and VCP/p97 in neurons may be applied to study of cancer and bone. Statin treatment rescues the spine defects caused by VCP deficiency, suggesting the potential role of statin in clinical treatment for these two diseases.

A nonsynonymous TNFRSF11A variation increases NFκB activity and the severity of Paget's disease

Mutations in the SQSTM1 gene were identified as a common cause of Paget's disease of bone (PDB) but experimental evidence demonstrated that SQSTM1 mutation is not sufficient to induce PDB in vivo. Here, we identified two nonsynonymous single nucleotide polymorphisms (SNPs) (C421T, H141Y and T575C, V192A) in the TNFRSF11A gene, associated with PDB and with the severity of phenotype in a large population of 654 unrelated patients that were previously screened for SQSTM1 gene mutations. The largest effect was found for the T575C variant, yielding an odds ratio of 1.29 (p = 0.003), with the C allele as the risk allele. Moreover, an even more significant p-value (p = 0.0002) was observed in the subgroup of patients with SQSTM1 mutation, with an odds ratio of 1.71. Interestingly, patients with the C allele also showed an increased prevalence of polyostotic disease (68%, 53%, and 51% in patients with CC, CT, and TT genotypes, respectively; p = 0.01), as well as an increased number of affected skeletal sites (2.9, 2.5, and 2.0 in patients with CC, CT, and TT genotypes, respectively, p = 0.008). These differences increased when analyses were restricted to cases with SQSTM1 mutation. In human cell lines, cotrasfection with mutated SQSTM1 and TNFRSF11A(A192) produced a level of activation of NFκB signaling greater than cotrasfection with wild-type SQSTM1 and TNFRSF11A(V192), confirming genetics and clinical evidences. These results provide the first evidence that genetic variation within the OPG/RANK/RANKL system influences the severity of PBD in synergistic action with SQSTM1 gene mutations.

Treatment of Paget's disease of bone

Paget's disease of bone is the paradigm of bone focal distortion with accelerated bone turnover. Over the years, a number of different drugs have been used to control its activity but, since biphosphonates were introduced for the treatment of the disease, they have become the preferred treatment. This review will update the therapeutic indications, available drugs and therapeutic response monitoring.

Autophagy shapes inflammation

Autophagy is a basic cell biological process ongoing under physiologic circumstances in almost all cell types of the human organism and upregulated by various stress conditions including those leading to inflammation. Since autophagy affects the effector cells of innate and adaptive immunity mediating the inflammatory response, its activity in these cells influences the antimicrobial response, the development of an effective cognate immune defense, and the course of the normal sterile inflammatory reactions. The level of autophagic activity may determine whether tissue cells die by apoptosis, necrosis, or through autophagy, and, as a consequence, whether the clearance of these dying cells is a silent process or results in an inflammatory response. Loss or decreased autophagy may lead to necrotic death that can initiate an inflammatory reaction in phagocytes through their surface and cytosolic receptors. Engulfment of certain cells dying through autophagy can activate the inflammasome. The intertwining regulatory connections between inflammation and immunity extend to pathologic conditions including chronic inflammatory diseases, autoimmunity and cancer.

Osteoclasts in the dental microenvironment: a delicate balance controls dental histogenesis

The impact of osteoclast activity on dental development has been previously analyzed but in the context of severe osteopetrosis. The present study sought to investigate the effects of osteoclast hypofunction,present in Msx2 gene knockin mutant mice (Msx2-/-), and hyperfunction, in transgenic mice driving RANK over-expression in osteoclast precursors (RANK(Tg)), on tooth development. In Msx2-/- mice, moderate osteopetrosis was observed, occurring exclusively in the periodontal region. Microradiographical and histological analyses revealed an abnormal dental epithelium histogenesis that gave rise to odontogenic tumor-like structures. This led to impaired tooth eruption, especially of the third mandibular molars. In RANK(Tg) mice, root histogenesis showed site-specific upregulation of dental cell proliferation and differentiation rates. This culminated in roots with a reduced diameter and pulp size albeit of normal length. These two reverse experimental systems will enable the investigation of distinctive dental cell and osteoclast communication in normal growth and tumorigenesis.

Emerging strategies and therapies for treatment of Paget's disease of bone

Paget's disease of bone (PDB) is a progressive monostotic or polyostotic metabolic bone disease characterized by focal abnormal bone remodeling, with increased bone resorption and excessive, disorganized, new bone formation. PDB rarely occurs before middle age, and it is the second most frequent metabolic bone disorder after osteoporosis, affecting up to 3% of adults over 55 years of age. One of the most striking and intriguing clinical features is the focal nature of the disorder, in that once the disease is established within a bone, there is only local spread within that bone and no systemic dissemination. Despite many years of intense research, the etiology of PDB has still to be conclusively determined. Based on a detailed review of genetic and viral factors incriminated in PDB, we propose a unifying hypothesis from which we can suggest emerging strategies and therapies. PDB results in weakened bone strength and abnormal bone architecture, leading to pain, deformity or, depending on the bone involved, fracture in the affected bone. The diagnostic assessment includes serum total alkaline phosphatase, total body bone scintigraphy, skull and enlarged view pelvis x-rays, and if needed, additional x-rays. The ideal therapeutic option would eliminate bone pain, normalize serum total alkaline phosphatase with prolonged remission, heal radiographic osteolytic lesions, restore normal lamellar bone, and prevent recurrence and complications. With the development of increasingly potent bisphosphonates, culminating in the introduction of a single intravenous infusion of zoledronic acid 5 mg, these goals of treatment are close to being achieved, together with long-term remission in almost all patients. Based on the recent pathophysiological findings, emerging strategies and therapies are reviewed: ie, pulse treatment with zoledronic acid; denosumab, a fully human monoclonal antibody directed against RANK ligand; tocilizumab, an interleukin-6 receptor inhibitor; odanacatib, a cathepsin K inhibitor; and proteasome and Dickkopf-1 inhibitors.

Processing of optineurin in neuronal cells

Optineurin is a gene linked to amyotrophic lateral sclerosis, Paget disease of bone, and glaucoma, a major blinding disease. Mutations such as E50K were identified in glaucoma patients. We investigated herein the involvement of ubiquitin-proteasome pathway (UPP) and autophagy, two major routes for protein clearance, in processing of optineurin in a retinal ganglion cell model line RGC5 and neuronal PC12 cells. It was found that the endogenous optineurin level in neuronal cells was increased by treatment of proteasomal inhibitor but not by autophagic and lysosomal inhibitors. Multiple bands immunoreactive to anti-ubiquitin were seen in the optineurin pulldown, indicating that optineurin was ubiquitinated. In cells overexpressing wild type and E50K optineurin, the level of the proteasome regulatory β5 subunit (PSMB5, indicative of proteasome activity) was reduced, whereas that for autophagy marker microtubule-associated protein 1 light chain 3 was enhanced compared with controls. Autophagosome formation was detected by electron microscopy. The foci formed after optineurin transfection were increased upon treatment of an autophagic inhibitor but were decreased by treatment of an inducer, rapamycin. Moreover, the level of optineurin-triggered apoptosis was reduced by rapamycin. This study thus provides compelling evidence that in a normal homeostatic situation, the turnover of endogenous optineurin involves mainly UPP. When optineurin is up-regulated or mutated, the UPP function is compromised, and autophagy comes into play. A decreased PSMB5 level and an induced autophagy were also demonstrated in vivo in retinal ganglion cells of E50K transgenic mice, validating and making relevant the in vitro findings.

Epidemiological, clinical, and genetic characteristics of Paget's disease of bone in a rural area of Calabria, Southern Italy

BACKGROUND

The prevalence of Paget's disease of bone (PDB) is unknown in peninsular Southern Italy, although an elevated clinical severity of the disease was reported in patients from Campania.

AIM

This study was performed to evaluate the epidemiological and genetic characteristics of PDB in a rural area of Calabria, the southernmost region in the Italian peninsula.

SUBJECTS AND METHODS

We examined 1068 consecutive pelvic radiographs of patients older than 40 yr referred for any reason to the "Spinelli" Hospital, Belvedere Marittimo, from January 1st 2004 to December 31st 2006. In subjects with radiological findings of pelvic PDB, a 99m Technetium methylene diphosphonate bone scan and the sequence analysis of the sequestosome 1 (SQSTM1) gene were subsequently performed.

RESULTS

In the examined geographic area, the crude radiographic prevalence of pelvic PDB was 0.74% (8/1068; male:female 5:3, mean age 71.6 ± 13.1 yr) whereas the estimated overall prevalence of PDB between 0.82% and 1.21%. PDB patients from Calabria showed clinical characteristics similar to those reported in patients from Campania. The disease was also frequently complicated by osteoarthritis and the right side of the body was more affected than the left. The SQSTM1 gene analysis revealed the presence of a novel missense mutation (M401V) in exon 8 in one subject with a familial and aggressive form of PDB.

CONCLUSION

The study results confirmed that patients with PDB from rural districts of Southern Italy show an earlier onset and an increased clinical severity of the disease that appears mostly independent from the presence of germinal SQSTM1 mutations.

Paget's disease of bone is not associated with common polymorphisms in interleukin-6, interleukin-8 and tumor necrosis factor alpha genes

BACKGROUND

Cytokines, specially interleukin (IL)-6, play an important role in the differentiation and activation of osteoclasts and might be involved in osteoblast stimulation in Paget's disease of bone (PDB).

OBJECTIVES

The aim of this study was to investigate the association of polymorphisms in IL-6, IL-8 and tumor necrosis factors-alpha (TNFA) genes among Spanish patients with PDB.

METHODS

We studied four single nucleotide polymorphisms (-174 G>C IL-6, -251 T>A IL-8, -238 G>A TNFA and -308 G>A TNFA) in 172 PDB patients and 150 healthy controls. Distribution of alleles and pro-inflammatory genotypes were studied for association with the presence of the disease and with clinical and laboratory data, as well as the response to bisphosphonate treatment in PDB patients.

RESULTS

We found no statistically significant association between genotype and allele distribution of any of the cytokines polymorphism studied and PDB. No association between the clinical and therapeutic characteristics of PDB and the investigated polymorphism were found.

CONCLUSIONS

This study does not support the hypothesis that the analyzed IL6, IL8 and TNFA polymorphism are associated with PDB.

Autophagy: cellular and molecular mechanisms

Autophagy is a self-degradative process that is important for balancing sources of energy at critical times in development and in response to nutrient stress. Autophagy also plays a housekeeping role in removing misfolded or aggregated proteins, clearing damaged organelles, such as mitochondria, endoplasmic reticulum and peroxisomes, as well as eliminating intracellular pathogens. Thus, autophagy is generally thought of as a survival mechanism, although its deregulation has been linked to non-apoptotic cell death. Autophagy can be either non-selective or selective in the removal of specific organelles, ribosomes and protein aggregates, although the mechanisms regulating aspects of selective autophagy are not fully worked out. In addition to elimination of intracellular aggregates and damaged organelles, autophagy promotes cellular senescence and cell surface antigen presentation, protects against genome instability and prevents necrosis, giving it a key role in preventing diseases such as cancer, neurodegeneration, cardiomyopathy, diabetes, liver disease, autoimmune diseases and infections. This review summarizes the most up-to-date findings on how autophagy is executed and regulated at the molecular level and how its disruption can lead to disease.

Early onset Paget's disease of bone caused by a novel mutation (78dup27) of the TNFRSF11A gene in a Chinese family

AIM

A previous study showed that individuals of Japanese descent affected by early onset familial Paget's disease of bone (PDB) carried a 27-bp duplication at position 75 (75dup27) in the TNFRSF11A gene encoding RANK. Here we report the identification of a novel mutation (78dup27) in exon 1 of TNFRSF11A in a Chinese family with early onset PDB.

METHODS

We conducted clinical and genetic studies in a non-consanguineous Chinese family with early onset PDB. The entire coding region of TNFRSF11A was amplified and directly sequenced directly.

RESULTS

A novel 27-bp duplication in exon 1 (78dup27) in TNFRSF11A was found in four affected individuals and one asymptomatic individual. Although this duplication was the same length as the previously identified mutation (27 bp, from bases 78 to 104), in our patients the nine duplicated amino acids in the RANK signal peptide were LLLLCALLA. The phenotypes of affected individuals in this family overlapped with both early onset PDB and classic PDB, but several distinguishing features were found in our patients. The key difference between our familial PDB and the Japanese early onset PDB was the age of onset, which in most of our patients was during their late 20s (except for the propositus' niece). Another notable difference was that the propositus' son (24 years old), who carried the 78dup27 mutation, had no clinical symptoms or bone abnormalities, except for increased serum ALP, OC and CTX.

CONCLUSION

Our findings may provide a better understanding of the clinical features of early onset PDB and support the notion of a hot spot for mutations in exon 1 of the TNFRSF11A gene.