ZNF687 Mutations in Severe Paget Disease of Bone Associated with Giant Cell Tumor

Early stress exposure on zebrafish development: effects on survival, malformations and molecular alterations

The effects of stress during early vertebrate development can be especially harmful. Avoiding stressors in fish larvae is essential to ensure the health of adult fish and their reproductive performance and overall production. We examined the consequences of direct exposure to successive acute stressors during early development, including their effects on miR-29a and its targets, survival, hatching and malformation rates, larval behaviour and cartilage and eye development. Our aim was to shed light on the pleiotropic effects of early-induced stress in this vertebrate model species. Our results showed that direct exposure to successive acute stressors during early development significantly upregulated miR-29a and downregulated essential collagen transcripts col2a1a, col6a2 and col11a1a, decreased survival and increased malformation rates (swim bladder, otoliths, cardiac oedema and ocular malformations), promoting higher rates of immobility in larvae. Our results revealed that stress in early stages can induce different eye tissular architecture and cranioencephalic cartilage development alterations. Our research contributes to the understanding of the impact of stressful conditions during the early stages of zebrafish development, serving as a valuable model for vertebrate research. This holds paramount significance in the fields of developmental biology and aquaculture and also highlights miR-29a as a potential molecular marker for assessing novel larval rearing programmes in teleost species.

Diagnosis and treatment of Paget's disease of bone: position paper from the Italian Society of Osteoporosis, Mineral Metabolism and Skeletal Diseases (SIOMMMS)

INTRODUCTION

Paget's disease of bone is a focal skeletal disorder causing bone deformities and impairing bone quality. Despite the prevalence of asymptomatic cases is increasing, the progression of the disease can lead to invalidating complications that compromise the quality of life. Doubts on clinical and therapeutic management aspects exist, although beneficial effects of antiresorptive drugs, particularly bisphosphonates are known. However, limited information is available from randomized controlled trials on the prevention of disease complications so that somewhat contrasting positions about treatment indications between expert panels from the main scientific societies of metabolic bone diseases exist. This task force, composed by expert representatives appointed by the Italian Society of Osteoporosis, Mineral Metabolism and Skeletal Diseases and members of the Italian Association of Paget's disease of bone, felt the necessity for more specific and up to date indications for an early diagnosis and clinical management.

METHODS

Through selected key questions, we propose evidence-based recommendations for the diagnosis and treatment of the disease. In the lack of good evidence to support clear recommendations, available information from the literature together with expert opinion of the panel was used to provide suggestions for the clinical practice.

RESULTS AND CONCLUSION

Description of the evidence quality and support of the strength of the statements was provided on each of the selected key questions. The diagnosis of PDB should be mainly based on symptoms and the typical biochemical and radiological features. While treatment is mandatory to all the symptomatic cases at diagnosis, less evidence is available on treatment indications in asymptomatic as well as in previously treated patients in the presence of biochemical recurrence. However, given the safety and long-term efficacy of potent intravenous bisphosphonates such as zoledronate, a suggestion to treat most if not all cases at the time of diagnosis was released.

Znf687 recruits Brd4-Smrt complex to regulate gfi1aa during neutrophil development

Neutrophils are key component of the innate immune system in vertebrates. Diverse transcription factors and cofactors act in a well-coordinated manner to ensure proper neutrophil development. Dysregulation of the transcriptional program triggering neutrophil differentiation is associated with various human hematologic disorders such as neutropenia, neutrophilia, and leukemia. In the current study we show the zinc finger protein Znf687 is a lineage-preferential transcription factor, whose deficiency leads to an impaired neutrophil development in zebrafish. Mechanistically, Znf687 functions as a negative regulator of gfi1aa, a pivotal modulator in terminal granulopoiesis, to regulate neutrophil maturation. Moreover, we found BRD4, an important epigenetic regulator, directly interacts with ZNF687 in neutrophils. Deficiency of brd4 results in similar defective neutrophil development as observed in znf687 mutant zebrafish. Biochemical and genetic analyses further reveal that instead of serving as a canonical transcriptional coactivator, Brd4 directly interacts and bridges Znf687 and Smrt nuclear corepressor on gfi1aa gene's promoter to exert transcription repression. In addition, the ZNF687-BRD4-SMRT-GFI1 transcriptional regulatory network is evolutionary conserved in higher vertebrate. Overall, our work indicates Znf687 and Brd4 are two novel master regulators in promoting terminal granulopoiesis.

Multifocal osteoclast-rich tumour in Paget bone disease and conventional giant cell tumour, two genetically distinct entities? Sequencing from a single case

Paget disease of bone is a metabolic disorder with a strong genetic component, characterised by pronounced disorganised bone remodelling. Complications of this disease include an increased risk of developing bone neoplasms. Here, we describe the case of a 60-year-old Italian patient with Paget disease of bone, presenting with an osteoclast-rich tumour. Our analysis of this entity, based on the clinical, morphological and genetic data (whole exome sequencing), suggests that osteoclast-rich lesions in Paget disease of bone are genetically distinct from classical giant cell tumour of bone. We discuss the importance of differentiating these osteoclast-rich lesions.

Genetic Screening of ZNF687 and PFN1 in a Paget's Disease of Bone Cohort Indicates an Important Role for the Nuclear Localization Signal of ZNF687

Paget's disease of bone (PDB) is a common, late-onset bone disorder, characterized by focal increases of bone turnover that can result in bone lesions. Heterozygous pathogenic variants in the Sequestosome 1 (SQSTM1) gene are found to be the main genetic cause of PDB. More recently, PFN1 and ZNF687 have been identified as causal genes in patients with a severe, early-onset, polyostotic form of PDB, and an increased likelihood to develop giant cell tumors. In our study, we screened the coding regions of PFN1 and ZNF687 in a Belgian PDB cohort (n = 188). In the PFN1 gene, no variants could be identified, supporting the observation that variants in this gene are extremely rare in PDB. However, we identified 3 non-synonymous coding variants in ZNF687. Interestingly, two of these rare variants (p.Pro937His and p.Arg939Cys) were clustering in the nuclear localization signal of the encoded ZNF687 protein, also harboring the p.Pro937Arg variant, a previously reported disease-causing variant. In conclusion, our findings support the involvement of genetic variation in ZNF687 in the pathogenesis of classical PDB, thereby expanding its mutational spectrum.

Osteolytic Bone Loss and Skeletal Deformities in a Mouse Model for Early-Onset Paget's Disease of Bone with PFN1 Mutation Are Treatable by Alendronate

A novel osteolytic disorder due to PFN1 mutation was discovered recently as early-onset Paget's disease of bone (PDB). Bone loss and pain in adult PDB patients have been treated using bisphosphonates. However, therapeutic strategies for this specific disorder have not been established. Here, we evaluated the efficiency of alendronate (ALN) on a mutant mouse line, recapitulating this disorder. Five-week-old conditional osteoclast-specific Pfn1-deficient mice (Pfn1-cKOOCL) and control littermates (33 females and 22 males) were injected with ALN (0.1 mg/kg) or vehicle twice weekly until 8 weeks of age. After euthanizing, bone histomorphometric parameters and skeletal deformities were analyzed using 3D μCT images and histological sections. Three weeks of ALN administration significantly improved bone mass at the distal femur, L3 vertebra, and nose in Pfn1-cKOOCL mice. Histologically increased osteoclasts with expanded distribution in the distal femur were normalized in these mice. Geometric bone shape analysis revealed a partial recovery from the distal femur deformity. A therapeutic dose of ALN from 5 to 8 weeks of age significantly improved systemic bone loss in Pfn1-cKOOCL mice and femoral bone deformity. Our study suggests that preventive treatment of bony deformity in early-onset PDB is feasible.

ZNF765 is a prognostic biomarker of hepatocellular carcinoma associated with cell cycle, immune infiltration, m6A modification, and drug susceptibility

Hepatocellular carcinoma (HCC) is an ongoing challenge worldwide. Zinc finger protein 765 (ZNF765) is an important zinc finger protein that is related to the permeability of the blood-tumor barrier. However, the role of ZNF765 in HCC is unclear. This study evaluated the expression of ZNF765 in hepatocellular carcinoma and the impact of its expression on patient prognosis based on The Cancer Genome Atlas (TCGA). Immunohistochemical assays (IHC) were used to examine protein expression. Besides, a colony formation assay was used to examine cell viability. We also explored the relationship between ZNF765 and chemokines in the HCCLM3 cells by qRT-PCR. Moreover, we examined the effect of ZNF765 on cell resistance by measurement of the maximum half-inhibitory concentration. Our research revealed that ZNF765 expression in HCC samples was higher than that in normal samples, whose upregulation was not conducive to the prognosis. The results of GO, KEGG, and GSEA showed that ZNF765 was associated with the cell cycle and immune infiltration. Furthermore, we confirmed that the expression of ZNF765 had a strong connection with the infiltration level of various immune cells, such as B cells, CD4+ T cells, macrophages, and neutrophils. In addition, we found that ZNF765 was associated with m6A modification, which may affect the progression of HCC. Finally, drug sensitivity testing found that patients with HCC were sensitive to 20 drugs when they expressed high levels of ZNF765. In conclusion, ZNF765 may be a prognostic biomarker related to cell cycle, immune infiltration, m6A modification, and drug sensitivity for hepatocellular carcinoma.

Genomic Profiling Reveals the Variant Landscape of Sporadic Parathyroid Adenomas in Chinese Population

OBJECTIVE

To define somatic variants of parathyroid adenoma (PA) and to provide novel insights into the underlying molecular mechanism of sporadic PA.

METHODS

Basic clinical characteristics and biochemical indices of 73 patients with PA were collected. Whole-exome sequencing was performed on matched tumor-constitutional DNA pairs to detect somatic alterations. Functional annotation was carried out by ingenuity pathway analysis afterward. The protein expression of the variant gene was confirmed by immunohistochemistry, and the relationship between genotype and phenotype was analyzed.

RESULTS

Somatic variants were identified in 1549 genes, with an average of 69 variants per tumor (range, 13-2109; total, 9083). Several novel recurrent somatic variants were detected, such as KMT2D (15/73), MUC4 (14/73), POTEH (13/73), CD22 (12/73), HSPA2 (12/73), HCFC1 (11/73), MAGEA1 (11/73), and SLC4A3 (11/73), besides the previously reported PA-related genes, including MEN1 (11/73), CASR (6/73), MTOR (4/73), ASXL3 (3/73), FAT1 (3/73), ZFX (5/73), EZH1 (2/73), POT1 (2/73), and EZH2 (1/73). Among them, KMT2D might be the candidate driver gene of PA. Crucially, 5 patients carried somatic mutations in CDC73, showed an aggressive phenotype similar to that of parathyroid carcinoma (PC), and had a decreased expression of parafibromin. Pathway analysis of recurrent potential PA-associated driver variant genes revealed functional enrichments in the signaling pathway of Notch.

CONCLUSION

Our study expanded the pathogenic variant spectrum of PA and indicated that KMT2D might be a novel candidate driver gene and be considered as a diagnostic biomarker for PA. Meanwhile, CDC73 mutations might be an early developmental event from PA to PC. The results provided insights into elucidating the pathogenesis of parathyroid tumorigenesis and a certain basis for clinical diagnosis and treatment.

Paget's disease: a review of the epidemiology, etiology, genetics, and treatment

Paget's disease of bone (PDB) is the second most prevalent metabolic bone disorder worldwide, with a prevalence rate of 1.5%-8.3%. It is characterized by localized areas of accelerated, disorganized, and excessive bone production and turnover. Typically, PDB develops in the later stages of life, particularly in the late 50s, and affects men more frequently than women. PDB is a complex disease influenced by both genetic and environmental factors. PDB has a complex genetic basis involving multiple genes, with SQSTM1 being the gene most frequently associated with its development. Mutations affecting the UBA domain of SQSTM1 have been detected in both familial and sporadic PDB cases, and these mutations are often associated with severe clinical expression. Germline mutations in other genes such as TNFRSF11A, ZNF687 and PFN1, have also been associated with the development of the disease. Genetic association studies have also uncovered several PDB predisposing risk genes contributing to the disease pathology and severity. Epigenetic modifications of genes involved in bone remodelling and regulation, including RANKL, OPG, HDAC2, DNMT1, and SQSTM1, have been implicated in the development and progression of Paget's disease of bone, providing insight into the molecular basis of the disease and potential targets for therapeutic intervention. Although PDB has a tendency to cluster within families, the variable severity of the disease across family members, coupled with decreasing incidence rates, indicates that environmental factors may also play a role in the pathophysiology of PDB. The precise nature of these environmental triggers and how they interact with genetic determinants remain poorly understood. Fortunately, majority of PDB patients can achieve long-term remission with an intravenous infusion of aminobisphosphonates, such as zoledronic acid. In this review, we discuss aspects like clinical characteristics, genetic foundation, and latest updates in PDB research.

Stress decreases spermatozoa quality and induces molecular alterations in zebrafish progeny

BACKGROUND

Chronic stress can produce a severe negative impact on health not only in the exposed individuals but also in their offspring. Indeed, chronic stress may be contributing to the current worldwide scenario of increasing infertility and decreasing gamete quality in human populations. Here, we evaluate the effect of chronic stress on behavior and male reproductive parameters in zebrafish. Our goal is to provide information on the impact that chronic stress has at molecular, histological, and physiological level in a vertebrate model species.

RESULTS

We evaluated the effects of a 21-day chronic stress protocol covering around three full waves of spermatogenesis in Danio rerio adult males. The induction of chronic stress produced anxiety-like behavior in stressed males as assessed by a novel tank test. At a molecular level, the induction of chronic stress consistently resulted in the overexpression of two genes related to endoplasmic reticulum (ER) stress in the brain. Gene set enrichment analysis (GSEA) of testes suggested a dysregulation of the nonsense-mediated decay (NMD) pathway, which was also confirmed on qPCR analysis. Histological analysis of the testicle did not show significant differences in terms of the relative proportions of each germ-cell type; however, the quality of sperm from stressed males was compromised in terms of motility. RNA-seq analysis in stress-derived larval progenies revealed molecular alterations, including those predicted to affect translation initiation, DNA repair, cell cycle control, and response to stress.

CONCLUSIONS

Induction of chronic stress during a few cycles of spermatogenesis in the vertebrate zebrafish model affects behavior, gonadal gene expression, final gamete quality, and progeny. The NMD surveillance pathway (a key cellular mechanism that regulates the stability of both normal and mutant transcripts) is severely affected in the testes by chronic stress and therefore the control and regulation of RNAs during spermatogenesis may be affected altering the molecular status in the progeny.

A mutation in the ZNF687 gene that is responsible for the severe form of Paget's disease of bone causes severely altered bone remodeling and promotes hepatocellular carcinoma onset in a knock-in mouse model

Paget's disease (PDB) is a late-onset bone remodeling disorder with a broad spectrum of symptoms and complications. One of the most aggressive forms is caused by the P937R mutation in the ZNF687 gene. Although the genetic involvement of ZNF687 in PDB has been extensively studied, the molecular mechanisms underlying this association remain unclear. Here, we describe the first Zfp687 knock-in mouse model and demonstrate that the mutation recapitulates the PDB phenotype, resulting in severely altered bone remodeling. Through microcomputed tomography analysis, we observed that 8-month-old mutant mice showed a mainly osteolytic phase, with a significant decrease in the trabecular bone volume affecting the femurs and the vertebrae. Conversely, osteoblast activity was deregulated, producing disorganized bone. Notably, this phenotype became pervasive in 16-month-old mice, where osteoblast function overtook bone resorption, as highlighted by the presence of woven bone in histological analyses, consistent with the PDB phenotype. Furthermore, we detected osteophytes and intervertebral disc degeneration, outlining for the first time the link between osteoarthritis and PDB in a PDB mouse model. RNA sequencing of wild-type and Zfp687 knockout RAW264.7 cells identified a set of genes involved in osteoclastogenesis potentially regulated by Zfp687, e.g., Tspan7, Cpe, Vegfc, and Ggt1, confirming its role in this process. Strikingly, in this mouse model, the mutation was also associated with a high penetrance of hepatocellular carcinomas. Thus, this study established an essential role of Zfp687 in the regulation of bone remodeling, offering the potential to therapeutically treat PDB, and underlines the oncogenic potential of ZNF687.

Regulation of human ZNF687, a gene associated with Paget's disease of bone

Mutations in Zinc finger 687 (ZNF687) were associated with Paget's disease of bone (PDB), a disease characterized by increased bone resorption and excessive bone formation. It was suggested that ZNF687 plays a role in bone differentiation and development. However, the mechanisms involved in ZNF687 regulation remain unknown. This study aimed to obtain novel knowledge regarding ZNF687 transcriptional and epigenetic regulation. Through in silico analysis, we hypothesized three ZNF687 promoter regions located upstream exon 1 A, 1B, and 1 C and denominated promoter regions 1, 2, and 3, respectively. Their functionality was confirmed by luciferase activity assays and positive/negative regulatory regions were identified using promoter deletions constructs. In silico analysis revealed a high density of CpG islands in these promoter regions and in vitro methylation suppressed promoters' activity. Using bioinformatic approaches, bone-associated transcription factor binding sites containing CpG dinucleotides were identified, including those for NFκB, PU.1, DLX5, and SOX9. By co-transfection in HEK293 and hFOB cells, we found that DLX5 specifically activated ZNF687 promoter region 1, and its methylation impaired DLX5-driven promoter stimulation. NFκB repressed and activated promoter regions 1 and 2, respectively, and these activities were affected by methylation. PU.1 induced ZNF687 promoter region 1 which was affected by methylation. SOX9 differentially regulated ZNF687 promoters in HEK293 and hFOB cells that were impaired after methylation. In conclusion, this study provides novel insights into ZNF687 regulation by demonstrating that NFκB, PU.1, DLX5, and SOX9 are regulators of ZNF687 promoters, and DNA methylation influences their activity. The contribution of the dysregulation of these mechanisms in PDB should be further elucidated.

Gene Sequencing Identifies Perturbation in Nitric Oxide Signaling as a Nonlipid Molecular Subtype of Coronary Artery Disease

BACKGROUND

A key goal of precision medicine is to disaggregate common, complex diseases into discrete molecular subtypes. Rare coding variants in the low-density lipoprotein receptor gene (LDLR) are identified in 1% to 2% of coronary artery disease (CAD) patients, defining a molecular subtype with risk driven by hypercholesterolemia.

METHODS

To search for additional subtypes, we compared the frequency of rare, predicted loss-of-function and damaging missense variants aggregated within a given gene in 41 081 CAD cases versus 217 115 controls.

RESULTS

Rare variants in LDLR were most strongly associated with CAD, present in 1% of cases and associated with 4.4-fold increased CAD risk. A second subtype was characterized by variants in endothelial nitric oxide synthase gene (NOS3), a key enzyme regulating vascular tone, endothelial function, and platelet aggregation. A rare predicted loss-of-function or damaging missense variants in NOS3 was present in 0.6% of cases and associated with 2.42-fold increased risk of CAD (95% CI, 1.80-3.26; P=5.50×10-9). These variants were associated with higher systolic blood pressure (+3.25 mm Hg; [95% CI, 1.86-4.65]; P=5.00×10-6) and increased risk of hypertension (adjusted odds ratio 1.31; [95% CI, 1.14-1.51]; P=2.00×10-4) but not circulating cholesterol concentrations, suggesting that, beyond lipid pathways, nitric oxide synthesis is a key nonlipid driver of CAD risk.

CONCLUSIONS

Beyond LDLR, we identified an additional nonlipid molecular subtype of CAD characterized by rare variants in the NOS3 gene.

Updates on Paget's Disease of Bone

Paget's disease of the bone is a prevalent bone disease characterized by disorganized bone remodeling; however, it is comparatively uncommon in East Asian countries, including China, Japan, and Korea. The exact cause still remains unknown. In genetically susceptible individuals, environmental triggers such as paramyxoviral infections are likely to cause the disease. Increased osteoclast activity results in increased bone resorption, which attracts osteoblasts and generates new bone matrix. Fast bone resorption and formation lead to the development of disorganized bone tissue. Increasing serum alkaline phosphatase or unique radiographic lesions may serve as the diagnostic indicators. Common symptoms include bone pain, bowing of the long bones, an enlarged skull, and hearing loss. The diagnosis is frequently confirmed by radiographic and nuclear scintigraphy of the bone. Further, bisphosphonates such as zoledronic acid and pamidronate are effective for its treatment. Moreover, biochemical monitoring is superior to the symptoms as a recurrence indicator. This article discusses the updates of Paget's disease of bone with a clinical case.

Where is bone science taking us?

Bone science has over the last decades unraveled many important pathways in bone and mineral metabolism and the interplay between genetic factors and the environment. Some of these discoveries have led to the development of pharmacological treatments of osteoporosis and rare bone diseases. Other scientific avenues have uncovered a role for the gut microbiome in regulating bone mass, which have led to investigations on the possible therapeutic role of probiotics in the prevention of osteoporosis. Huge advances have been made in identifying the genes that cause rare bone diseases, which in some cases have led to therapeutic interventions. Advances have also been made in understanding the genetic basis of the more common polygenic bone diseases, including osteoporosis and Paget's disease of bone (PDB). Polygenic profiles are used for establishing genetic risk scores aiming at early diagnosis and intervention, but also in Mendelian randomization (MR) studies to investigate both desired and undesired effects of targets for drug design.

Update on the pathogenesis and genetics of Paget’s disease of bone

Studies over the past two decades have led to major advances in the pathogenesis of Paget’s disease of bone (PDB) and particularly on the role of genetic factors. Germline mutations of different genes have been identified, as a possible cause of this disorder, and most of the underlying pathways are implicated in the regulation of osteoclast differentiation and function, whereas other are involved in cell autophagy mechanisms. In particular, about 30 different germline mutations of the Sequestosome 1 gene (SQSTM1) have been described in a significant proportion of familial and sporadic PDB cases. The majority of SQSTM1 mutations affect the ubiquitin-binding domain of the protein and are associated to a more severe clinical expression of the disease. Also, germline mutations in the ZNF687 and PFN1 genes have been associated to severe, early onset, polyostotic PDB with increased susceptibly to neoplastic degeneration, particularly giant cell tumor. Mutations in the VCP (Valosin Containing Protein) gene cause the autosomal dominant syndrome “Inclusion Body Myopathy, PDB, Fronto-temporal Dementia,” characterized by pagetic manifestations, associated with myopathy, amyotrophic lateral sclerosis and fronto-temporal dementia. Moreover, germline mutations in the TNFRSF11A gene, which encodes for RANK, were associated with rare syndromes showing some histopathological, radiological, and clinical overlap with PDB and in two cases of early onset PDB-like disease. Likewise, genome wide association studies performed in unrelated PDB cases identified other potential predisposition genes and/or susceptibility loci. Thus, it is likely that polygenic factors are involved in the PDB pathogenesis in many individuals and that modifying genes may contribute in refining the clinical phenotype. Moreover, the contribution of somatic mutations of SQSTM1 gene and/or epigenetic mechanisms in the pathogenesis of skeletal pagetic abnormalities and eventually neoplastic degeneration, cannot be excluded. Indeed, clinical and experimental observations indicate that genetic susceptibility might not be a sufficient condition for the clinical development of PDB without the concomitant intervention of viral infection, in primis paramixoviruses, and/or other environmental factors (e.g., pesticides, heavy metals or tobacco exposure), at least in a subset of cases. This review summarizes the most important advances that have been made in the field of cellular and molecular biology PDB over the past decades.

The Osteoclast Traces the Route to Bone Tumors and Metastases

Osteoclasts are highly specialized cells of the bone, with a unique apparatus responsible for resorption in the process of bone remodeling. They are derived from differentiation and fusion of hematopoietic precursors, committed to form mature osteoclasts in response to finely regulated stimuli produced by bone marrow-derived cells belonging to the stromal lineage. Despite a highly specific function confined to bone degradation, emerging evidence supports their relevant implication in bone tumors and metastases. In this review, we summarize the physiological role of osteoclasts and then focus our attention on their involvement in skeletal tumors, both primary and metastatic. We highlight how osteoclast-mediated bone erosion confers increased aggressiveness to primary tumors, even those with benign features. We also outline how breast and pancreas cancer cells promote osteoclastogenesis to fuel their metastatic process to the bone. Furthermore, we emphasize the role of osteoclasts in reactivating dormant cancer cells within the bone marrow niches for manifestation of overt metastases, even decades after homing of latent disseminated cells. Finally, we point out the importance of counteracting tumor progression and dissemination through pharmacological treatments based on a better understanding of molecular mechanisms underlying osteoclast lytic activity and their recruitment from cancer cells.

Primary Benign Tumors of the Spinal Canal

Benign tumors that grow in the spinal canal are heterogeneous neoplasms with low incidence; from these, meningiomas and nerve sheath tumors (neurofibromas and schwannomas) account for 60%-70% of all primary spinal tumors. Benign spinal canal tumors provoke nonspecific clinical manifestations, mostly related to the affected level of the spinal cord. These tumors present a challenge for the patient and healthcare professionals, for they are often difficult to diagnose and the high frequency of posttreatment complications. In this review, we describe the epidemiology, risk factors, clinical features, diagnosis, histopathology, molecular biology, and treatment of extramedullary benign meningiomas, osteoid osteomas, osteoblastomas, aneurysmal bone cysts, osteochondromas, neurofibromas, giant cell tumors of the bone, eosinophilic granulomas, hemangiomas, lipomas, and schwannomas located in the spine, as well as possible future targets that could lead to an improvement in their management.

Clinical Characteristics and Pathogenic Gene Identification in Chinese Patients With Paget's Disease of Bone

OBJECTIVE

To evaluate the clinical features of sporadic Paget's disease of bone (PDB) in China and further explore the underlying genetic abnormalities of the disease.

METHODS

Clinical characteristics, biochemical indices, bone turnover markers and radiographic examinations of the patients were collected. Genomic DNA was extracted from peripheral blood and whole-exome sequencing was carried out to identify the potential pathogenic genes. The pathogenicity of the variants was thereafter investigated by bioinformatics analysis.

RESULTS

A total of 50 patients (57.20 ± 15.52 years, male/female: 1.63: 1) with PDB were included and the mean onset age was 48.34 years (48.34 ± 17.24 years). 94.0% of the patients exhibited symptomatic patterns described as bone pain (86.0%), elevated skin temperature at the lesion site (26.0%), bone deformity (22.0%) and local swelling (18.0%). The most frequently involved lesion sites were pelvis (52.0%), femur (42.0%), tibia (28.0%), skull (28.0%) and spine (18.0%), respectively. Additionally, 40.0% of them accompanied with osteoarthritis, 14.0% with pathological fractures, and the misdiagnosis rate of PDB was as high as 36.0%. Serum level of alkaline phosphatase was significantly increased, with the mean value of 284.00 U/L (quartiles, 177.00-595.00 U/L). Two heterozygous missense mutations of SQSTM1 gene (c.1211T>C, M404T) and one novel heterozygous missense mutation in HNRNPA2B1 gene (c.989C>T, p. P330L) were identified in our study. Moreover, several potential disease-causing genes were detected and markedly enriched in the pathways of neurodegeneration (including WNT16, RYR3 and RYR1 genes) and amyotrophic lateral sclerosis (ALS, including NUP205, CAPN2, and NUP214 genes).

CONCLUSION

In contrast to Western patients, Chinese patients have an earlier onset age, more severe symptoms, and lower frequency of SQSTM1 gene mutation (4.0%). Moreover, a novel heterozygous missense mutation in HNRNPA2B1 gene was identified in one male patient with isolated bone phenotype. As for other genetic factors, it was indicated that WNT16, RYR3, RYR1, NUP205, CAPN2 and NUP214 genes may be potential pathogenic genes, pathways of neurodegeneration and ALS may play a vital role in the pathogenesis of PDB.

A Panel-Based Sequencing Analysis of Patients with Paget's Disease of Bone Suggests Enrichment of Rare Genetic Variation in regulators of NF-κB Signaling and Supports the Importance of the 7q33 Locus

Paget's disease of bone (PDB) is a common bone disorder characterized by focal lesions caused by increased bone turnover. Monogenic forms of PDB and PDB-related phenotypes as well as genome-wide association studies strongly support the involvement of genetic variation in components of the NF-κB signaling pathway in the pathogenesis of PDB. In this study, we performed a panel-based mutation screening of 52 genes. Single variant association testing and a series of gene-based association tests were performed. The former revealed a novel association with NFKBIA and further supports an involvement of variation in NR4A1, VCP, TNFRSF11A, and NUP205. The latter indicated a trend for enrichment of rare genetic variation in GAB2 and PRKCI. Both single variant tests and gene-based tests highlighted two genes, NR4A1 and NUP205. In conclusion, our findings support the involvement of genetic variation in modulators of NF-κB signaling in PDB and confirm the association of previously associated genes with the pathogenesis of PDB.

Targeted Inactivation of Rin3 Increases Trabecular Bone Mass by Reducing Bone Resorption and Favouring Bone Formation

Common genetic variants at the RIN3 locus on chromosome 14q32 predispose to Paget's disease of bone (PDB) but the mechanisms by which they do so are unknown. Here, we analysed the skeletal phenotype of female mice with targeted inactivation of the mouse Rin3 gene (Rin3^-/-) as compared with wild-type littermates. The Rin3^-/- mice had higher trabecular bone volume (BV/TV%) compared with wild type. Mean ± standard deviation values at the distal femur at 8 weeks were 9.0 ± 2.5 vs. 7.0 ± 1.5 (p = 0.002) and at 52 weeks were 15.8 ± 9.5 vs. 8.5 ± 4.2 (p = 0.002). No differences were observed in femoral cortical bone parameters with the exception of marrow diameter which was significantly smaller in 52-week-old Rin3^-/- mice compared to wild type: (0.43 mm ± 0.1 vs. 0.57 mm ± 0.2 (p = 0.001). Bone histomorphometry showed a lower osteoclast surface / bone surface (Oc.S/BS%) at 8 weeks in Rin3^-/- mice compared to wild type (24.1 ± 4.7 vs. 29.7 ± 6.6; p = 0.025) but there were no significant differences in markers of bone formation at this time. At 52 weeks, Oc.S/BS did not differ between genotypes but single labelled perimeter (SL.Pm/B.Pm (%)) was significantly higher in Rin3^-/- mice (24.4 ± 6.4 vs. 16.5 ± 3.8, p = 0.003). We conclude that Rin3 negatively regulates trabecular bone mass in mice by inhibiting osteoclastic bone resorption and favouring bone formation. Our observations also suggest that the variants that predispose to PDB in humans probably do so by causing a gain-in-function of RIN3.

Early Alpine occupation backdates westward human migration in Late Glacial Europe

Before the end of the Last Glacial Maximum (LGM, ∼16.5 ka ago)¹ set in motion major shifts in human culture and population structure,² a consistent change in lithic technology, material culture, settlement pattern, and adaptive strategies is recorded in Southern Europe at ∼18-17 ka ago. In this time frame, the landscape of Northeastern Italy changed considerably, and the retreat of glaciers allowed hunter-gatherers to gradually recolonize the Alps.^3-6 Change within this renewed cultural frame (i.e., during the Late Epigravettian phase) is currently associated with migrations favored by warmer climate linked to the Bølling-Allerød onset (14.7 ka ago),^7-11 which replaced earlier genetic lineages with ancestry found in an individual who lived ∼14 ka ago at Riparo Villabruna, Italy, and shared among different contexts (Villabruna Cluster).⁹ Nevertheless, these dynamics and their chronology are still far from being disentangled due to fragmentary evidence for long-distance interactions across Europe.¹² Here, we generate new genomic data from a human mandible uncovered at Riparo Tagliente (Veneto, Italy), which we directly dated to 16,980-16,510 cal BP (2σ). This individual, affected by focal osseous dysplasia, is genetically affine to the Villabruna Cluster. Our results therefore backdate by at least 3 ka the diffusion in Southern Europe of a genetic component linked to Balkan/Anatolian refugia, previously believed to have spread during the later Bølling/Allerød event. In light of the new genetic evidence, this population replacement chronologically coincides with the very emergence of major cultural transitions in Southern and Western Europe.

Mutations in Profilin 1 Cause Early-Onset Paget's Disease of Bone With Giant Cell Tumors

Paget's disease of bone (PDB) is a late-onset chronic progressive bone disease characterized by abnormal activation of osteoclasts that results in bone pain, deformities, and fractures. PDB is very rare in Asia. A subset of PDB patients have early onset and can develop malignant giant cell tumors (GCTs) of the bone (PDB/GCTs), which arise within Paget bone lesions; the result is a significantly higher mortality rate. SQSTM1, TNFRSF11A, OPG, VCP, and HNRNPA2B1 have been identified as pathogenic genes of PDB, and ZNF687 is the only confirmed gene to date known to cause PDB/GCT. However, the molecular mechanism underlying PDB/GCT has not been fully elucidated. Here, we investigate an extended Chinese pedigree with eight individuals affected by early-onset and polyostotic PDB, two of whom developed GCTs. We identified a heterozygous 4-bp deletion in the Profilin 1 (PFN1) gene (c.318_321delTGAC) by genetic linkage analysis and exome sequencing for the family. Sanger sequencing revealed another heterozygous 1-bp deletion in PFN1 (c.324_324delG) in a sporadic early-onset PDB/GCT patient, further proving its causative role. Interestingly, a heterozygous missense mutation of PFN1 (c.335 T > C) was identified in another PDB/GCT family, revealing that not only deletion but also missense mutations in PFN1 can cause PDB/GCT. Furthermore, we established a Pfn1-mutated mouse model (C57BL/6J mice) and successfully obtained Pagetic phenotypes in heterozygous mice, verifying loss of function of PFN1 as the cause of PDB/GCT development. In conclusion, our findings reveal mutations in PFN1 as the pathological mechanism in PDB/GCT, and we successfully established Pfn1-mutated mice as a suitable animal model for studying PDB-associated pathological mechanisms. The identification of PFN1 mutations has great diagnostic value for identifying PDB individuals predisposed toward developing GCTs. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Genetic Determinants of Paget's Disease of Bone

PURPOSE OF REVIEW

To provide an overview of the role of genes and loci that predispose to Paget's disease of bone and related disorders.

RECENT FINDINGS

Studies over the past ten years have seen major advances in knowledge on the role of genetic factors in Paget's disease of bone (PDB). Genome wide association studies have identified six loci that predispose to the disease whereas family based studies have identified a further eight genes that cause PDB. This brings the total number of genes and loci implicated in PDB to fourteen. Emerging evidence has shown that a number of these genes also predispose to multisystem proteinopathy syndromes where PDB is accompanied by neurodegeneration and myopathy due to the accumulation of abnormal protein aggregates, emphasising the importance of defects in autophagy in the pathogenesis of PDB. Genetic factors play a key role in the pathogenesis of PDB and the studies in this area have identified several genes previously not suspected to play a role in bone metabolism. Genetic testing coupled to targeted therapeutic intervention is being explored as a way of halting disease progression and improving outcome before irreversible skeletal damage has occurred.

Giant Cell Tumor of Bone in Patients under 16 Years Old: A Single-Institution Case Series

Simple Summary

Giant cell tumor of the bone is a locally aggressive, rarely metastasizing tumor that accounts for about 5% of bone tumors; it generally occurs in patients between 20 and 45 years old. Sporadic cases (less than 140) have been described as occurring in the first two decades of life. A histone 3.3 (H3.3) gene, H3F3A, has been recently identified in as many as 96% of giant cell tumors of bone. These mutations are useful in the differential diagnosis of giant cell tumor of bone with its mimickers. The immunohistochemical expression of H3F3A resulted comparable to molecular analysis as reported in a recent investigation. In the present study, we describe our series of giant cell tumors of bone in pediatric patients <16 years old.

Abstract

Background: Giant cell tumor of bone is a locally aggressive, rarely metastasizing tumor that accounts for about 5% of bone tumors and generally occurs in patients between 20 and 45 years old. A driver mutation in the histone 3.3 (H3.3) gene H3F3A has been identified in as many as 96% of giant cell tumors of bone. The immunohistochemical expression of H3F3A H3.3 G34 expression was found in 97.8% of cases. In the present study, we describe our series of cases of giant cell tumor of bone in pediatric patients <16 years old. Methods: All cases of giant cell tumor of bone in pediatric patients <16 years old treated in our institute between 1982 and 2018 were reviewed. Immunohistochemistry and/or molecular analysis for H3F3A gene mutations was performed to confirm the diagnosis. A group of aneurysmal bone cysts in patients <16 years old was used as a control group. Results: Fifteen cases were retrieved. A pronounced female predominance (93%) was observed. A pure metaphyseal central location occurs in 2 skeletally immature patients. Conclusions: Giant cell tumor of bone should be distinguished from its mimickers due to differences in prognosis and treatment. Immunohistochemical and molecular detection of H3F3A gene mutation represents a reliable diagnostic tool.

Hepatocyte growth factor overexpression promotes osteoclastogenesis and exacerbates bone loss in CIA mice

Background

Hepatocyte growth factor (HGF) is a multifunctional growth factor that promotes various biological processes. However, the effect of HGF on bone metabolism in rheumatoid arthritis (RA) remains unknown. Here, we investigated the role of HGF in regulating osteoclastogenesis and bone resorption in RA.

Methods

The expression of HGF in RA patients and collagen-induced arthritis (CIA) mice was examined. The role of HGF on osteoclastogenesis was analysed by osteoclastogenesis and bone resorption assays. The effect of HGF inhibition was evaluated in a CIA mice model. The mechanism of HGF in regulating osteoclastogenesis and bone resorption was explored by a series of in vitro studies.

Results

HGF was overexpressed in CIA and RA. HGF stimulated osteoclastogenesis in vitro. SU11274, a selective small molecule blocker of c-Met, impeded the effect of HGF on osteoclastogenesis and bone resorption. HGF regulated osteoclastogenesis by JNK and AKT-GSK-3β-NFATc1 signallings. SU11274 protected CIA mice from pathological bone loss.

Conclusions

These data strongly suggest that the highly expressed HGF in the joint tissues contributes to bone loss in RA. Inhibition of HGF/c-Met could effectively alleviate pathological bone loss and inflammatory symptoms in CIA mice. HGF/c-Met may be used as a new target for the treatment of bone loss in RA.

ZNF687 Mutations in an Extended Cohort of Neoplastic Transformations in Paget's Disease of Bone: Implications for Clinical Pathology

Neoplastic transformation is a rare but serious complication of Paget's disease of bone (PDB), occurring in fewer than 1% of individuals with polyostotic disease. Their prognosis is poor, with less than 50% surviving 5 years. In 2016, the genetic alteration of giant cell tumor (GCT) complicating PDB was identified as a founder germline mutation (P937R) in the ZNF687 gene. However, the study population was exclusively of Italian descent, and patients of different ethnic origins were not studied. To fill this gap, herein we performed mutation analysis of ZNF687 in a GCT in the pelvis of a 45-year-old black American woman with polyostotic PDB. The P937R mutation in ZNF687 was found in her tumor but, as expected, the ancestral haplotype that characterizes the Italian GCT/PDB patients was not found. Furthermore, we identified two additional Italian GCT/PDB patients with this ZNF687 mutation, now constituting a cohort of 18 GCT/PDB cases, all harboring the identical mutation. We also searched for ZNF687 mutations in a unique collection of tumor tissues derived from Italian PDB patients, including 28 osteosarcomas (OS/PDB), 8 undifferentiated sarcomas (SRC/PDB), 1 fibrosarcoma (FS/PDB), and 1 chondrosarcoma (CS/PDB). We identified the P937R mutation in one SRC/PDB and a different ZNF687 mutation (R331W) in 1 of 28 pagetic osteosarcomas. Thus, whereas GCT/PDB pathogenesis globally seems to involve the P937R mutation in ZNF687, other neoplasms associated with PDB seem to be less related to mutations in this gene. Finally, we identified the G34W mutation in the H3F3A gene in the maxillary tumor masses of two PDB patients, defining them as conventional GCT rather than GCT/PDB. Thus, combined molecular analysis of H3F3A and ZNF687 is essential to clarify the origin and diagnosis of tumors in PDB. © 2020 American Society for Bone and Mineral Research.

Whole-Exome Sequencing Identifies Novel Compound Heterozygous ZNF469 Mutations in Two Siblings with Mild Brittle Cornea Syndrome

Connective tissue diseases, including osteogenesis imperfecta (OI) and Ehlers-Danlos syndrome (EDS), exhibit a high degree of clinical and genetic heterogeneity. We report two sisters with blue sclerae, joint hypermobility and hearing loss. Whole-exome sequencing identified two compound heterozygous ZNF469 loss-of-function mutations due to a frameshift. Since these findings indicate the presence of brittle cornea syndrome (BCS), we performed ocular optical coherence tomography (OCT) and pachymetry, which revealed a moderate decrease in corneal thickness. While only one traumatic fracture was observed in each of the patients, a detailed skeletal assessment indicated no specific patterns of bone mass and microstructure reduction as well as normal bone turnover markers. Taken together, our findings point to a mild form of brittle cornea syndrome with a phenotype compatible with the extraskeletal features of OI but also with EDS.

The Loss of Profilin 1 Causes Early Onset Paget's Disease of Bone

Paget's disease of bone (PDB) is a late-onset disorder frequently caused by mutations in the SQSTM1 gene, leading to hyperactive osteoclasts and resulting in bone pain, deformities, and fractures. However, some more severe forms of PDB-negative for SQSTM1 mutations-have been described, in which the disease degenerates into bone cancers and shows a poor prognosis. Osteosarcoma is the most frequent and aggressive tumor arising in PDB (OS/PDB), with a 5-year survival rate almost nil, but the underlying molecular mechanism is unknown. Here, we investigated an extended pedigree with 11 individuals affected by early onset and polyostotic PDB, mainly interesting the appendicular skeleton. Interestingly, three members also developed secondary osteosarcoma. We performed exome sequencing and identified a 4-bp deletion in the PFN1 gene, resulting in the degradation of the mutant protein. Copy number screening on 218 PDB individuals of our biobank disclosed that four of them (~2%) carry a germline heterozygous deletion of PFN1. The identification of these subjects, who exhibit a particularly severe form of disease, emphasizes the diagnostic value of this genetic screening to identify PDB individuals predisposed to develop osteosarcoma. In fact, we detected allelic imbalance at PFN1 locus also in 8 of 14 (57%) sporadic OS/PDB, further proving its causative role. in vitro experiments also confirmed PFN1 involvement in this form of PDB. Indeed, CRISPR-Cas9-mediated Pfn1 knockout in pre-osteoclasts resulted into enhanced osteoclast differentiation and resorption, with the formation of large osteoclasts never described before in PDB. In addition, Pfn1 lacking pre-osteoblasts lost their differentiation capability and failed to efficiently mineralize bone. Moreover, they acquired features of malignant transformation, including loss of focal adhesions and increased invasion ability. In conclusion, these findings disclose PFN1 haploinsufficiency as the pathological mechanism in OS/PDB. © 2020 American Society for Bone and Mineral Research.

Mutation of PFN1 Gene in an Early Onset, Polyostotic Paget-like Disease

CONTEXT

Paget disease of bone (PDB) is a metabolic bone disease whose genetic cause remains unknown in up to 50% of familial patients.

OBJECTIVE

Our aim was to investigate the underlying genetic defect in a large pedigree with a severe, early onset, autosomal dominant form of PDB across 3 generations.

METHODS

Whole exome sequencing was performed in affected and unaffected family members, and then mutation screening was replicated in a sample of PDB patients with early-onset, polyostotic PDB.

RESULTS

We identified a frameshift D107Rfs*3 mutation in PFN1 (encoding for profilin 1, a highly conserved regulator of actin-polymerization and cell motility) causing the truncation of the C-terminal part of the protein. The mutation was also detected in a 17-year-old asymptomatic family member who upon biochemical and radiological analyses was indeed found to be affected. Sequencing of the entire PFN1 coding region in unrelated PDB patients identified the same mutation in 1 patient. All mutation carriers had a reduced response to bisphosphonates, requiring multiple zoledronate infusions to control bone pain and achieve biochemical remission over a long term. In vitro osteoclastogenesis in peripheral blood mononuclear cells (PBMCs) from mutation carriers showed a higher number of osteoclasts with PDB-like features. A similar phenotype was observed upon PFN1 silencing in murine bone marrow-derived monocytes, suggesting that the frameshift PFN1 mutation confers a loss of function in profilin 1 activity that induces PDB-like features in the osteoclasts, likely due to enhanced cell motility and actin ring formation.

CONCLUSIONS

Our findings indicate that PFN1 mutation causes an early onset, polyostotic PDB-like disorder.

The two faces of giant cell tumor of bone

Giant cell tumor (GCT) is a bone-destructive benign neoplasm characterized by distinctive multinucleated osteoclast-like giant cells with osteolytic properties distributed among neoplastic stromal cells. GCT is locally aggressive with progressive invasion of adjacent tissues and occasionally displays malignant characteristics including lung metastasis. GCT is characterized genetically by highly recurrent somatic mutations at the G34 position of the H3F3A gene, encoding the histone variant H3.3, in stromal cells. This leads to deregulated gene expression and increased proliferation of mutation-bearing cells. However, when GCT complicates Paget disease of bone (GCT/PDB) it behaves differently, showing a more malignant phenotype with 5-year survival less than 50%. GCT/PDB is caused by a germline mutation in the ZNF687 gene, which encodes a transcription factor involved in the repression of genes surrounding DNA double-strand breaks to promote repair by homologous recombination. Identification of these driver mutations led to novel diagnostic tools for distinguishing between these two tumors and other osteoclast-rich neoplasms. Herein, we review the clinical, histological, and molecular features of GCT in different contexts focusing also on pharmacological treatments.

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.

The evaluation and treatment of Paget's disease of bone

Paget's disease of bone is a localized skeletal disorder, which is more common in England and in countries to which the English migrated. In recent decades, the prevalence in most countries has decreased. A family history of the disorder is present in approximately 15% of patients. Patients may be asymptomatic and may be diagnosed accidently as a consequence of an elevated serum alkaline phosphatase level or a finding on an x-ray or nuclear bone scan. The diagnosis is made by x-ray but nuclear bone scans define the extent of the disease. Salmon calcitonin and bisphosphonate drugs have proven effective, but by far, the most effective therapy is a single 5 mg intravenous infusion of zoledronic acid. This can normalize alkaline phosphatase levels for up to 6.5 years. A variety of gene mutations may predispose individuals to develop the disease but environmental factors such as measles virus likely play an important role.

Paget's Disease of Bone

Paget's disease of bone (PDB) is a chronic and focal bone disorder, characterized by increased osteoclast-mediated bone resorption and a subsequent compensatory increase in bone formation, resulting in a disorganized mosaic of woven and lamellar bone at one or more affected skeletal sites. As a result, bone pain, noticeable deformities, arthritis at adjacent joints, and fractures can occur. In a small proportion of cases neoplastic degeneration in osteosarcoma, or, less frequently, giant cell tumor has been also described at PDB sites. While recent epidemiological evidences clearly indicate a decrease in the prevalence and the severity of PDB, over the past 2 decades there have been consistent advances on the genetic mechanisms of disease. It is now clear that PDB is a genetically heterogeneous disorder, with mutations in at least two different genes (SQSTM1, ZNF687) and more common predisposing variants. As a counterpart to the genetic hypothesis, the focal nature of lesions, the decline in prevalence rates, and the incomplete penetrance of the disease among family members suggest that one or more environmental triggers may play a role in the pathophysiology of PDB. The exact nature of these triggers and how they might interact with the genetic factors are less understood, but recent experimental data from mice models suggest the implication of paramixoviral infections. The clinical management of PDB has also evolved considerably, with the development of potent aminobisphosphonates such as zoledronic acid which, given as a single intravenous infusion, now allows a long-term disease remission in the majority of patients.

Molecular insights into an ancient form of Paget's disease of bone

We identify an ancient and atypical form of Paget’s disease of bone (PDB) in a collection of medieval skeletons exhibiting unusually extensive pathological changes, high disease prevalence, and low age-at-death estimations. Proteomic analysis of ancient bone-preserved proteins combined with analysis of small RNAs supports a retrospective diagnosis of PDB. Remains affected by other skeletal disorders may therefore hold a chemical memory amenable to similar molecular interrogation. Abnormalities in a contemporary PDB-linked protein detected in ancient tooth samples indicate that dentition may represent an unexplored storehouse for the study of skeletal disorders. Our work provides insights into the natural history of PDB and prompts a similar revaluation of other archaeological collections.

Paget’s disease of bone (PDB) is a chronic skeletal disorder that can affect one or several bones in individuals older than 55 y of age. PDB-like changes have been reported in archaeological remains as old as Roman, although accurate diagnosis and natural history of the disease is lacking. Six skeletons from a collection of 130 excavated at Norton Priory in the North West of England, which dates to medieval times, show atypical and extensive pathological changes resembling contemporary PDB affecting as many as 75% of individual skeletons. Disease prevalence in the remaining collection is high, at least 16% of adults, with age at death estimations as low as 35 y. Despite these atypical features, paleoproteomic analysis identified sequestosome 1 (SQSTM1) or p62, a protein central to the pathological milieu of PDB, as one of the few noncollagenous human sequences preserved in skeletal samples. Targeted proteomic analysis detected >60% of the ancient p62 primary sequence, with Western blotting indicating p62 abnormalities, including in dentition. Direct sequencing of ancient DNA excluded contemporary PDB-associated SQSTM1 mutations. Our observations indicate that the ancient p62 protein is likely modified within its C-terminal ubiquitin-associated domain. Ancient miRNAs were remarkably preserved in an osteosarcoma from a skeleton with extensive disease, with miR-16 expression consistent with that reported in contemporary PDB-associated bone tumors. Our work displays the use of proteomics to inform diagnosis of ancient diseases such as atypical PDB, which has unusual features presumably potentiated by yet-unidentified environmental or genetic factors.

Zinc-Based Biomaterials for Regeneration and Therapy

Zinc has been described as the 'calcium of the twenty-first century'. Zinc-based degradable biomaterials have recently emerged thanks to their intrinsic physiological relevance, biocompatibility, biodegradability, and pro-regeneration properties. Zinc-based biomaterials mainly include: metallic zinc alloys, zinc ceramic nanomaterials, and zinc metal-organic frameworks (MOFs). Metallic zinc implants degrade at a desirable rate, matching the healing pace of local tissues, and stimulating remodeling and formation of new tissues. Zinc ceramic nanomaterials are also beneficial for tissue engineering and therapy thanks to their nanostructures and antibacterial properties. MOFs have large surface areas and are easily functionalized, making them ideal for drug delivery and cancer therapy. This review highlights recent developments in zinc-based biomaterials, discusses obstacles to overcome, and pinpoints directions for future research.

Diagnosis and Management of Paget's Disease of Bone in Adults: A Clinical Guideline

An evidence-based clinical guideline for the diagnosis and management of Paget's disease of bone (PDB) was developed using GRADE methodology, by a Guideline Development Group (GDG) led by the Paget's Association (UK). A systematic review of diagnostic tests and pharmacological and nonpharmacological treatment options was conducted that sought to address several key questions of clinical relevance. Twelve recommendations and five conditional recommendations were made, but there was insufficient evidence to address eight of the questions posed. The following recommendations were identified as the most important: 1) Radionuclide bone scans, in addition to targeted radiographs, are recommended as a means of fully and accurately defining the extent of metabolically active disease in patients with PDB. 2) Serum total alkaline phosphatase (ALP) is recommended as a first-line biochemical screening test in combination with liver function tests in screening for the presence of metabolically active PDB. 3) Bisphosphonates are recommended for the treatment of bone pain associated with PDB. Zoledronic acid is recommended as the bisphosphonate most likely to give a favorable pain response. 4) Treatment aimed at improving symptoms is recommended over a treat-to-target strategy aimed at normalizing total ALP in PDB. 5) Total hip or knee replacements are recommended for patients with PDB who develop osteoarthritis in whom medical treatment is inadequate. There is insufficient information to recommend one type of surgical approach over another. The guideline was endorsed by the European Calcified Tissues Society, the International Osteoporosis Foundation, the American Society of Bone and Mineral Research, the Bone Research Society (UK), and the British Geriatric Society. The GDG noted that there had been a lack of research on patient-focused clinical outcomes in PDB and identified several areas where further research was needed. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Targeted sequencing of DCSTAMP in familial Paget's disease of bone

Paget's disease of bone (PDB) has a strong genetic component. Variants in SQSTM1 are found in up to 40% of patients with a family history of the disease, where a pattern of autosomal dominance with incomplete penetrance is apparent. By contrast, SQSTM1 variants are only found in up to 10% of patients with sporadic disease. It has been hypothesised that the remaining genetic susceptibility to PDB, particularly in familial cases, could be explained by rare genetic variants in loci previously identified by Genome Wide Association Studies. It is likely that polygenic factors are involved in many individuals. In this study we utilised whole exome sequencing to investigate predisposing genetic factors in an unsolved PDB kindred and identified a c.1189C > T p.L397F variant in DC-STAMP, also known as TM7SF4, that co-segregated with disease. DCSTAMP was identified as a gene of interest in PDB following Genome Wide Association Studies and has been previously shown to play critical roles in osteoclast fusion. The variant we identified has also been reported in association with PDB in a French-Canadian cohort however the significance of this variant was inconclusive. Targeted screening of DCSTAMP in our familial cohort of PDB patients revealed an additional 8 variants; however we did not find a significant association between any of these, including p.L397F, with PDB. Osteoclastogenesis assays from the affected proband and his unaffected brother demonstrated an increase in osteoclast number and nucleation, consistent with the pagetic phenotype. In converse to other established Paget's associated genetic variations such as SQSTM1, TNFRSF11A and OPTN, expression of the mutant DC-STAMP protein attenuated the activation of transcription factors NFκB and AP-1 when exogenously expressed. We found that the p.L397F variant did not influence the subcellular localization of the protein. Based on these findings we conclude that genetic variation in DCSTAMP is not a significant predisposing factor in our specific cohort of PDB patients and the p.L397F variant is unlikely to be a contributing factor in PDB pathogenesis.

•

Variants in DC-STAMP do not appear to be significantly associated with Paget’s disease of bone in our cohort.

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The DC-STAMP p.L397F variant attenuates both NFkB and AP-1 signalling compared to the wild type protein.

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No significant differences in cellular colocalisation were found between DC-STAMP wild type and p.L397F.

An update of molecular pathology of bone tumors. Lessons learned from investigating samples by next generation sequencing

The last decade has seen the majority of primary bone tumor subtypes become defined by molecular genetic alteration. Examples include giant cell tumour of bone (H3F3A p.G34W), chondroblastoma (H3F3B p.K36M), mesenchymal chondrosarcoma (HEY1-NCOA2), chondromyxoid fibroma (GRM1 rearrangements), aneurysmal bone cyst (USP6 rearrangements), osteoblastoma/osteoid osteoma (FOS/FOSB rearrangements), and synovial chondromatosis (FN1-ACVR2A and ACVR2A-FN1). All such alterations are mutually exclusive. Many of these have been translated into clinical service using immunohistochemistry or FISH. 60% of central chondrosarcoma is characterised by either isocitrate dehydrogenase (IDH) 1 or IDH2 mutations distinguishing them from other cartilaginous tumours. In contrast, recurrent alterations which are clinically helpful have not been found in high grade osteosarcoma. High throughput next generation sequencing has also proved valuable in identifying germ line alterations in a significant proportion of young patients with primary malignant bone tumors. These findings will play an increasing role in reaching a diagnosis and in patient management.

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.

Paget's disease of bone

Paget's disease of bone is a focal disorder of bone remodelling that progresses slowly and leads to changes in the shape and size of affected bones and to skeletal, articular and vascular complications. In some parts of the world it is the second most common bone disorder after osteoporosis though in recent years its prevalence and severity appear to decrease. The disease is easily diagnosed and effectively treated but its pathogenesis remains incompletely understood.

Variations in nuclear localization strategies among pol X family enzymes

Despite the essential roles of pol X family enzymes in DNA repair, information about the structural basis of their nuclear import is limited. Recent studies revealed the unexpected presence of a functional nuclear localization signal (NLS) in DNA polymerase β, indicating the importance of active nuclear targeting, even for enzymes likely to leak into and out of the nucleus. The current studies further explore the active nuclear transport of these enzymes by identifying and structurally characterizing the functional NLS sequences in the three remaining human pol X enzymes: terminal deoxynucleotidyl transferase (TdT), DNA polymerase mu (pol μ) and DNA polymerase lambda (pol λ). NLS identifications are based on Importin α (Impα) binding affinity determined by fluorescence polarization of fluorescein-labeled NLS peptides, X-ray crystallographic analysis of the Impα∆IBB•NLS complexes and fluorescence-based subcellular localization studies. All three polymerases use NLS sequences located near their N-terminus; TdT and pol μ utilize monopartite NLS sequences, while pol λ utilizes a bipartite sequence, unique among the pol X family members. The pol μ NLS has relatively weak measured affinity for Impα, due in part to its proximity to the N-terminus that limits non-specific interactions of flanking residues preceding the NLS. However, this effect is partially mitigated by an N-terminal sequence unsupportive of Met1 removal by methionine aminopeptidase, leading to a 3-fold increase in affinity when the N-terminal methionine is present. Nuclear targeting is unique to each pol X family enzyme with variations dependent on the structure and unique functional role of each polymerase.

Human Genetics of Sclerosing Bone Disorders

PURPOSE OF REVIEW

The group of sclerosing bone disorders encompasses a variety of disorders all marked by increased bone mass. In this review, we give an overview of the genetic causes of this heterogeneous group of disorders and briefly touch upon the value of these findings for the development of novel therapeutic agents.

RECENT FINDINGS

Advances in the next-generation sequencing technologies are accelerating the molecular dissection of the pathogenic mechanisms underlying skeletal dysplasias. Throughout the years, the genetic cause of these disorders has been extensively studied which resulted in the identification of a variety of disease-causing genes and pathways that are involved in bone formation by osteoblasts, bone resorption by osteoclasts, or both processes. Due to this rapidly increasing knowledge, the insights into the regulatory mechanisms of bone metabolism are continuously improving resulting in the identification of novel therapeutic targets for disorders with reduced bone mass and increased bone fragility.

ZNF687 mutations are frequently found in pagetic patients from South Italy: implication in the pathogenesis of Paget's disease of bone

Paget's disease of bone (PDB) is a skeletal disorder whose molecular basis is not fully elucidated. However, 10% of patients show a familial PDB and 35% of them carry mutations in the SQSTM1 gene. We recently reported a founder mutation (p.Pro937Arg) in the ZNF687 gene, underlying PDB complicated by giant cell tumor (GCT/PDB) and rarely occurring in PDB patients without neoplastic degeneration. Since 80% of Italian GCT/PDB patients derive from Avellino, we hypothesized that ZNF687 mutation rate was higher in this region than elsewhere. Interestingly, our molecular analysis on 30 PDB patients showed that 33% hosted ZNF687 mutations, with the p.Pro937Arg identified in 8 familial cases. Two novel ZNF687 mutations (p.Pro665Leu and p.Gln784Glu) were detected in 2 sporadic patients. Only 2 subjects were positive for the p.Pro392Leu mutation in SQSTM1. ZNF687-mutated patients showed a severe PDB, with a remarkable number of affected sites. in vitro studies revealed that the ZNF687-mutant osteoclasts appeared as giant sized with up to 150 nuclei, never described in PDB. Finally, we also confirmed the causality of the p.Pro937Arg mutation in 4 additional GCT/PDB cases deriving from the same geographic area, indicating that PDB and GCT/PDB represent 2 sides of the same coin.

The identification of H3F3A mutation in giant cell tumour of the clivus and the histological diagnostic algorithm of other clival lesions permit the differential diagnosis in this location

BACKGROUND

Giant Cell Tumour of Bone (GCT) is a locally aggressive primary bone tumour that usually occurs at the epiphyses of the long bones of the appendicular skeleton with a tendency to recurrence. Recurrent somatic H3F3A mutations have been described in 92% of GCT cases. GCTs involving the Clivus are extremely rare lesions and less than 15 cases are described in the literature. They represent a surgery challenge and are easily misdiagnosed. Our aim was to reveal if the genetic bases underlying Clival GCTs were the same of GCTs of long bones to improve the diagnosis and treatment.

METHODS

The targeted somatic sequencing of GCT-related genes (H3F3A, H3F3B, IDH1, IDH2 and ZNF687) was performed on Clival GCT biopsies of two different cases. Histological analyses on the same tissues were used to detect the neoplastic population and its expression profile.

RESULTS

Sanger sequencing revealed that both patients were positive for the p.Gly34Trp mutation in the H3F3A gene. Immunofluorescence assay using monoclonal antibody, specifically detecting the mutant H3.3, highlighted that the mutation only involved the mononuclear cell population and not the multinucleated giant cells. Moreover, immunohistochemistry assay showed that RANKL was highly expressed by the stromal cells within Clival GCT, mimicking what happens in GCT of the long bones. In addition, systematic literature review allowed us to generate a histology-based diagnostic algorithm of the most common clival lesions.

CONCLUSIONS

We conclude that the Clival GCT is genetically defined by somatic mutation in the H3F3A gene, linking it to the GCT of long bones. The similarity with GCTs of long bones let us to hypothesize the utility of Denosumab therapy (already effective for GCTs) in these surgically challenging cases. Moreover, H3F3A genetic screening can be combined to the histological analysis to differentiate GCTs from morphologically similar giant cell-rich sarcomas, while the histological diagnostic algorithm could help the differential diagnosis of other clival lesions.

Paget's disease of bone

Paget's disease is a chronic focal high turnover bone disorder that is primarily present in middle-aged or older adults. It seems to be restricted to humans and has no clear parallels with other diseases. Although much has been learnt about its pathology and epidemiology, and treatment is now highly effective we still lack a complete understanding of its etiology and biology. This review focusses on the natural history of the disorder, in particular its changing epidemiology, recent discoveries about its genetic basis and current approaches to diagnosis and treatment. While there is strong evidence for genetic predisposition to Paget's disease, there is also compelling evidence that it is becoming less prevalent, the age of patients at presentation is increasing and that the extent of skeletal involvement is diminishing, implying that there is an important, but as yet unidentified, environmental factor in its etiology. Contemporary patients are typically elderly and have few bones involved. Treatment with potent intravenous bisphosphonates provides prolonged remission and many will require only once in a lifetime treatment.