Genetic variation in the TNFRSF11A gene encoding RANK is associated with susceptibility to Paget's disease of bone

Parallel and convergent evolution in genes underlying seasonal migration

Seasonal migration has fascinated scientists and natural historians for centuries. While the genetic basis of migration has been widely studied across different taxa, there is little consensus regarding which genomic regions play a role in the ability to migrate and whether they are similar across species. Here, we examine the genetic basis of intraspecific variation within and between distinct migratory phenotypes in a songbird. We focus on the Common Yellowthroat (Geothlypis trichas) as a model system because the polyphyletic origin of eastern and western clades across North America provides a strong framework for understanding the extent to which there has been parallel or convergent evolution in the genes associated with migratory behavior. First, we investigate genome-wide population genetic structure in the Common Yellowthroat in 196 individuals collected from 22 locations across breeding range. Then, to identify candidate genes involved in seasonal migration, we identify signals of putative selection in replicate comparisons between resident and migratory phenotypes within and between eastern and western clades. Overall, we find wide-spread support for parallel evolution at the genic level, particularly in genes that mediate biological timekeeping. However, we find little evidence of parallelism at the individual SNP level, supporting the idea that there are multiple genetic pathways involved in the modulation of migration.

RANK/RANKL Signaling Pathway in Breast Development and Cancer

RANK pathway has attracted increasing interest as a promising target in breast cancer, given the availability of denosumab, an anti-RANKL drug. RANK signaling mediates progesterone-driven regulation of mammary gland development and favors breast cancer initiation by controlling mammary cell proliferation and stem cell fate. RANK activation promotes luminal mammary epithelial cell senescence, acting as an initial barrier to tumorigenesis but ultimately facilitating tumor progression and metastasis. Comprehensive analyses have demonstrated that RANK protein expression is an independent biomarker of poor prognosis in postmenopausal and estrogen receptor-negative breast cancer patients. RANK pathway also has multiple roles in immunity and inflammation, regulating innate and adaptive responses. In the tumor microenvironment, RANK and RANKL are expressed by different immune cell populations and contribute to the regulation of tumor immune surveillance, mainly driving immunosuppressive effects.Herein, we discuss the preventive and therapeutic potential of targeting RANK signaling in breast cancer given its tumor cell intrinsic and extrinsic effects. RANKL inhibition has been shown to induce mammary tumor cell differentiation and an antitumor immune response. Moreover, loss of RANK signaling increases sensitivity of breast cancer cells to chemotherapy, targeted therapies such as HER2 and CDK4/6 inhibitors, and immunotherapy. Finally, we describe clinical trials of denosumab for breast cancer prevention, such as those ongoing in women with high risk of developing breast cancer, large phase III clinical trials where the impact of adjuvant denosumab on disease-free survival has been assessed, and window trials to evaluate the immunomodulatory effects of denosumab in breast cancer and other solid tumors.

Psoriasis, bone and bowel: a comprehensive review and new insights

Psoriasis is a chronic immune-mediated disorder affecting about 2% of the population worldwide which is associated with significant morbidity. The disease usually presents as raised, well-demarcated erythematous plaques with adherent silvery scales. Psoriasis can appear at any age but it has two peaks occurring at 15–20 and 55–60 years of age. It affects males and females equally. Despite the multitude of investigations about psoriasis and even development of drugs with satisfactory results, its pathogenesis is not fully understood yet and its course is unpredictable. Various environmental triggers, e.g., obesity, stress and drugs may induce disease in genetically susceptible patients. Although psoriasis was considered primarily as a disease of the skin, more investigations have been revealed its systemic nature. Psoriatic arthritis (PsA) may complicate up to one-third of cases of psoriasis vulgaris (PV). Also, the association between psoriasis and a variety of other immune-mediated disorders such as inflammatory bowel disease (IBD) and celiac disease (CD) has been confirmed in various studies. Moreover, a growing body of evidences indicates that psoriasis shares some common histological and phenotypical properties with the spectrum of osteoimmunological diseases such as Paget’s disease of bone (PDB). Thus, exploring the common molecular and genetic mechanisms underlying psoriasis and related disorders is of paramount importance for better elucidating disease pathogenesis and designing more targeted treatments.

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.

[Paget's disease of bone: 1877-2023. Etiology, and management of a disease on epidemiologic transition]

Paget's disease of bone is characterized by the alteration, in one or several bone locations, of the equilibrium between bone formation and bone resorption. This imbalance results in a disorganized, widened bone, in many cases with increased bone density, although more fragile. A genetic predisposition for Paget's disease of bone could explain between 5% and 40% of the cases. Different environmental factors should explain the rest of the cases. Paget's disease of bone was classically considered the second most common metabolic bone disease. However, in recent decades there has been a marked decrease in both incidence and clinical severity. These changes have led to believe that the influence of some environmental factor may have diminished or even disappeared. This decrease in incidence should not be an excuse for abandoning Paget's disease of bone research, but rather it should be the reason to remain searching to try to understand better its pathogenesis.

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.

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.

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.

Investigation of The Relationship of TNFRSF11A Gene Polymorphisms with Breast Cancer Development and Metastasis Risk in Patients with BRCA1 Or BRCA2 Pathogenic Variants Living in The Trakya Region of Turkey

Modifying genes play an exclusive role in the genetic regulation of the risk of breast cancer development in women with a pathogenic variation of BRCA1 or BRCA2. Therefore, it has been suggested that TNFRSF11A, which is among those modifying genes present in breast cancer development, may have a significant role in patients with positive BRCA1 or BRCA2 variations. In our study, we investigated the probable effects of single nucleotide polymorphisms (SNPs) in the TNFRSF11A gene, such as rs4485469, rs9646629, rs34739845, rs17069904, rs 884205, rs4941129 on the risk of breast cancer in patients with BRCA1 or BRCA2 variations. A total of 23 breast cancer patients with pathogenic variations in the BRCA1 or BRCA2 genes, 28 patients with no pathogenic variations in the BRCA1 or BRCA2 genes, and 55 healthy women as a control group, were included in this study. The SNPs were determined with allelic discrimination analysis through the real-time polymerase chain reaction (qPCR) method. There was no statistically significant difference between the SNPs of the TNFRSF11A gene rs4485469, rs9646629, rs34739845, rs17069904, rs884205, rs4941129 and metastasis, estrogen receptor, progesterone receptor and CerB2 receptor positivity between patient and control group (p >0.05). However, the rs4485469 SNP was found to be borderline significant between the patient groups with and without BRCA1 or BRCA2 mutations (p = 0.059). In patients with BRCA1 or BRCA2 pathogenic variations living in the Trakya region of Turkey, we could not determine the relationship between TNFRSF11 SNPs with breast cancer risk.

Association of RANK and RANKL gene polymorphism with survival and calcium levels in multiple myeloma

Multiple myeloma (MM) is a heterogeneous bone marrow cancer characterized by proliferation of malignant plasma cells in the bone marrow. One of its major symptoms are hypercalcaemia and bone lesions, which may result in pathologic bone fractures. Receptor activator for nuclear factor κB (RANK) and its ligand, RANKL, are part of an activation pathway for osteoclasts and are thus responsible for bone resorption. Furthermore, RANKL expression is increased in multiple myeloma. In the present study, we investigated the role of single nucleotide polymorphisms (SNPs) in the genes coding for RANK (rs1805034, rs8086340), RANKL (rs7325635, rs7988338), and TACI (rs34562254), a receptor for osteoclast-derived pro-survival factors. The study involved 222 patients and 222 healthy individuals, and the analysis included disease susceptibility, survival, bone lesions, calcium levels, and vascular endothelial growth factor levels. Patients with allele RANK rs1805034 C had higher survival (p = .003). This relationship was especially evident in women (p = .006). Furthermore, allele rs1805034 C was associated with slightly lower median age at diagnosis (64.0 vs. 65.5, p = .008). Allele RANKL rs7325635 A correlated with lower progression-free survival (p = .027), and with lack of early progression (p = .023). Additionally, women with allele rs7325635 G were found to have higher calcium blood concentration (p = .040). Allele TACI rs34562254 A was more common in MM patients in more advanced stages (II and III stage International Staging System) at diagnosis (p = .017), and the SNP showed a slight trend towards association in a multivariate analysis (p = .084). Taken together, our results suggest that RANK rs1805034 and RANKL rs7325635 may have a role in MM development and progression.

GWAS of Post-Orthodontic Aggressive External Apical Root Resorption Identified Multiple Putative Loci at X-Y Chromosomes

Personalized dental medicine requires from precise and customized genomic diagnostic. To conduct an association analysis over multiple putative loci and genes located at chromosomes 2, 4, 8, 12, 18, X, and Y, potentially implicated in an extreme type of external apical root resorption secondary to orthodontic forces (aEARR). A genome-wide association study of aEARR was conducted with 480 patients [ratio~1:3 case/control]. Genomic DNA was extracted and analyzed using the high-throughput Axiom platform with the GeneTitan^® MC Instrument. Up to 14,377 single nucleotide polymorphisms (SNPs) were selected at candidate regions and clinical/diagnostic data were recorded. A descriptive analysis of the data along with a backward conditional binary logistic regression was used to calculate odds ratios, with 95% confidence intervals [p < 0.05]. To select the best SNP candidates, a logistic regression model was fitted assuming a log-additive genetic model using R software [p < 0.0001]. In this sample the top lead genetic variants associated with aEARR were two novel putative genes located in the X chromosome, specifically, STAG 2 gene, rs151184635 and RP1-30E17.2 gene, rs55839915. These variants were found to be associated with an increased risk of aEARR, particularly restricted to men [OR: 6.09; 95%CI: 2.6–14.23 and OR: 6.86; 95%CI: 2.65–17.81, respectively]. Marginal associations were found at previously studied variants such as SSP1: rs11730582 [OR: 0.54; 95%CI: 0.34–0.86; p = 0.008], P2RX7: rs1718119 [OR: 0.6; 95%CI: 0.36–1.01; p = 0.047], and TNFRSF11A: rs8086340 [OR: 0.6; 95%CI: 0.38–0.95; p = 0.024]), found solely in females. Multiple putative genetic variants located at chromosomes X and Y are potentially implicated in an extreme phenotype of aEARR. A gender-linked association was noted.

Polymorphisms within the RANK and RANKL Encoding Genes in Patients with Rheumatoid Arthritis: Association with Disease Progression and Effectiveness of the Biological Treatment

Inconsistency of the results regarding the genetic variability within genes coding for receptor activator of nuclear factor κB (RANK) and its ligand (RANKL) in rheumatoid arthritis (RA) prompted us to study the RANK and RANKL polymorphisms as potential biomarkers associated with disease predisposition and response to anti-TNF treatment in a group of Polish patients with RA. This study enrolled 318 RA patients and 163 controls. RANK (rs8086340, C > G; rs1805034, C > T) and RANKL (rs7325635, G > A; rs7988338 G > A) alleles were determined by real-time PCR with melting curve analysis and related with clinical parameters. In addition, RANKL serum levels were measured by ELISA. The RANK rs8086340-G allele was overrepresented among patients as compared to controls (OD = 1.777, p = 0.038). C-reactive protein (CRP) levels were significantly (p < 0.05) associated with RANK rs8086340 polymorphism and were higher in the CC-homozygotes at the baseline while lower in the GG-carriers at the 12th week of the treatment. At the latter time point RANKL rs7325635-GG-positive patients also showed significantly lower CRP concentrations. Higher alkaline phosphatase levels before induction of anti-TNF therapy were observed in RANK rs8086340 and RANK rs1805034 CC homozygotes (p = 0.057 and p = 0.035, respectively). The GG homozygosity of both RANKL single nucleotide polymorphisms was significantly associated with the number of swollen joints (rs7988338 and rs7325635, before and at the 12th week of therapy, respectively, p < 0.05 in both cases). These results imply that polymorphisms within the RANK and RANKL genes affect RA susceptibility and anti-TNF treatment outcome.

Association of clinical variables and polymorphisms in RANKL, RANK, and OPG genes with external apical root resorption

OBJECTIVES

The aim of this study was to investigate the association of clinical variables and polymorphisms in the RANKL, RANK, and OPG genes with external apical root resorption (EARR).

METHODS

The sample was composed of 338 unrelated patients of both sexes, average age 14.9 years (range 8-21) with Class II Division 1 malocclusion, orthodontically treated. Periapical radiographs of the maxillary central incisor with the longer root (reference tooth) were taken before treatment and 6 months after starting treatment. DNA was extracted from buccal epithelial cells with the use of 10 mol/L ammonium acetate and 1 mmol/L EDTA. The analysis of 42 polymorphisms in the RANKL, RANK, and OPG genes was performed by means of real-time polymerase chain reaction. Univariate and multivariate analyzes were performed to verify the association of clinical and genetic variables with EARR (P <0.05).

RESULTS

The initial root length and patient age were associated with EARR. Considering the study of polymorphisms of RANKL, no significant association was found of genetic polymorphisms with EARR. For RANK polymorphisms, only rs12455775 was associated with EARR. Regarding OPG polymorphisms, an association of rs3102724, rs2875845, rs1032128, and rs3102728 with EARR was found. After multivariate analysis, the initial root length, rapid maxillary expansion, and rs3102724 of the OPG gene were associated with EARR.

CONCLUSIONS

Longer roots of upper central incisors and rapid maxillary expansion, as well as allele A of the rs3102724 polymorphism of the OPG gene, were associated with EARR in the study population.

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.

Genetic control of bone mass

Bone mineral density (BMD) is a quantitative traits used as a surrogate phenotype for the diagnosis of osteoporosis, a common metabolic disorder characterized by increased fracture risk as a result of a decreased bone mass and deterioration of the microarchitecture of the bone. Normal variation in BMD is determined by both environmental and genetic factors. According to heritability studies, 50-85% of the variance in BMD is controlled by genetic factors which are mostly polygenic. In contrast to the complex etiology of osteoporosis, there are disorders with deviating BMD values caused by one mutation with a large impact. These mutations can result in monogenic bone disorders with either an extreme high (sclerosteosis, Van Buchem disease, osteopetrosis, high bone mass phenotype) or low BMD (osteogenesis imperfecta, juvenile osteoporosis, primary osteoporosis). Identification of the disease causing genes, increased the knowledge on the regulation of BMD and highlighted important signaling pathways and novel therapeutic targets such as sclerostin, RANKL and cathepsin K. Genetic variation in genes involved in these pathways are often also involved in the regulation of normal variation in BMD and osteoporosis susceptibility. In the last decades, identification of genetic factors regulating BMD has proven to be a challenge. Several approaches have been tested such as linkage studies and candidate and genome wide association studies. Although, throughout the years, technological developments made it possible to study increasing numbers of genetic variants in populations with increasing sample sizes at the same time, only a small fraction of the genetic impact can yet be explained. In order to elucidate the missing heritability, the focus shifted to studying the role of rare variants, copy number variations and epigenetic influences. This review summarizes the genetic cause of different monogenic bone disorders with deviating BMD and the knowledge on genetic factors explaining normal variation in BMD and osteoporosis risk.

Development of a molecular test of Paget's disease of bone

Depending on populations, 15 to 40% of patients have a familial form of Paget's disease of bone (PDB), which is transmitted in an autosomal-dominant mode of inheritance with incomplete penetrance. To date, only SQSTM1 gene mutations have been linked to the disease. Several single nucleotide polymorphisms (SNPs) have been associated with PDB in patient non-carriers of SQSTM1 mutations, but they have minor size effects. The current clinical practice guidelines still recommend to measure total serum alkaline phosphatase (sALP) for PDB screening. However, genetic or bone biomarkers alone may lack sensitivity to detect PDB. Thus, the objective of this study was to develop a molecular test of PDB, combining genetic and bone biomarkers, in order to detect PDB, which is frequently asymptomatic. We genotyped 35 SNPs previously associated with PDB in 305 patients, and 292 healthy controls. In addition, serum levels of 14 bone biomarkers were assayed in 51 patients and 151 healthy controls. Bivariate and multivariate logistic regression models with adjustment for age and sex were fitted to search for a combination of SNPs and/or bone biomarkers that could best detect PDB in patient non-carriers of SQSTM1 mutations. First, a combination of five genetic markers gave rise to the highest area under the ROC curve (AUC) with 95% confidence interval [95% CI] of 0.731 [0.688; 0.773], which allowed us to detect 81.5% of patients with PDB. Second, a combination of two bone biomarkers had an AUC of 0.822 [0.726; 0.918], and was present in 81.5% of patients with PDB. Then, the combination of the five genetic markers and the two bone biomarkers increased the AUC up to 0.892 [0.833; 0.951], and detected 88.5% of patients with PDB. These results suggested that an algorithm integrating first a screen for SQSTM1 gene mutations, followed by either a genetic markers combination or a combined genetic and biochemical markers test in patients non-carrier of any SQSTM1 mutation, may detect the PDB phenotype better than biomarkers already available in the clinical practice.

Genetics of Paget's disease of bone

Paget's disease of bone (PDB) is a common metabolic bone disease characterised by focal areas of increased bone turnover, which primarily affects people over the age of 55 years. Genetic factors have a fundamental role in the pathogenesis of PDB and are probably the main predisposing factor for the disease. The genetic contribution to PDB susceptibility ranges from rare pathogenic mutations in the single gene SQSTM1 to more common, small effect variants in at least seven genetic loci that predispose to the disease. These loci have additive effects on disease susceptibility and interact with SQSTM1 mutations to affect disease severity, making them a potentially useful tool in predicting disease risk and complication and in managing treatments. Many of these loci harbour genes that have important function in osteoclast differentiation such as CSF1, DCSTAMP and TNFRSF11A. Other susceptibility loci have highlighted new molecular pathways that have not been previously implicated in regulation of bone metabolism such as OPTN, which was recently found to negatively regulate osteoclast differentiation. PDB-susceptibility variants exert their effect either by affecting the protein coding sequence such as variants found in SQSTM1 and RIN3 or by influencing gene expression such as those found in OPTN and DCSTAMP. Epidemiological studies indicate that environmental triggers also have a key role in PDB and interact with genetic factors to influence manifestation and severity of the disease; however, further studies are needed to identify these triggers.

The association between RANKL and Osteoprotegerin gene polymorphisms with breast cancer

Breast cancer is the most common cause of cancer death among women (522,000 deaths in 2012). Imbalance between RANKL and OPG is observed in many cancers, including breast cancer. Consequently, SNPs in the genes of RANKL and OPG may be involved in breast cancer development. This study included 276 subjects. Group I (n = 100) healthy females as a control group, group II (n = 96) breast cancer patients without bone metastases, and group III (n = 80) breast cancer patients with bone metastases. RANKL rs9533156, OPG rs2073618, and OPG rs2073617 SNPs and their serum protein levels were studied for a possible association with breast cancer development. The allele frequency [(OR: 4.832 CI 2.18-10.71, P = 0.001) and genotype distribution (P = 0.001)] of OPG SNP rs2073618 showed a highly significant difference between breast cancer patients and healthy controls. The allele C is more common in breast cancer patients. The allele frequency [(OR: 0.451 CI 0.232-0.879, P = 0.018) and genotype distribution (P = 0.003)] of RANKL SNP rs9533156 differed significantly between breast cancer patients and healthy controls. The allele T is more common in breast cancer patients. The allele frequency [(OR: 0.36 CI 0.184-0.705, P = 0.002) and genotype distribution (P = 0.011)] of OPG SNP rs2073617 differed significantly between breast cancer patients and healthy controls. The allele T is more common in breast cancer patients. The C allele of OPG SNP rs2073618 may be associated with breast cancer development. No association was found between any of the SNPs and the serum protein levels of RANKL and OPG.

Juvenile Paget's disease with heterozygous duplication within TNFRSF11A encoding RANK

Mendelian disorders of RANKL/OPG/RANK signaling feature the extremes of aberrant osteoclastogenesis and cause either osteopetrosis or rapid turnover skeletal disease. The patients with autosomal dominant accelerated bone remodeling have familial expansile osteolysis, early-onset Paget's disease of bone, expansile skeletal hyperphosphatasia, or panostotic expansile bone disease due to heterozygous 18-, 27-, 15-, and 12-bp insertional duplications, respectively, within exon 1 of TNFRSF11A that encodes the signal peptide of RANK. Juvenile Paget's disease (JPD), an autosomal recessive disorder, manifests extremely fast skeletal remodeling, and is usually caused by loss-of-function mutations within TNFRSF11B that encodes OPG. These disorders are ultra-rare. A 13-year-old Bolivian girl was referred at age 3years. One femur was congenitally short and curved. Then, both bowed. Deafness at age 2years involved missing ossicles and eroded cochleas. Teeth often had absorbed roots, broke, and were lost. Radiographs had revealed acquired tubular bone widening, cortical thickening, and coarse trabeculation. Biochemical markers indicated rapid skeletal turnover. Histopathology showed accelerated remodeling with abundant osteoclasts. JPD was diagnosed. Immobilization from a femur fracture caused severe hypercalcemia that responded rapidly to pamidronate treatment followed by bone turnover marker and radiographic improvement. No TNFRSF11B mutation was found. Instead, a unique heterozygous 15-bp insertional tandem duplication (87dup15) within exon 1 of TNFRSF11A predicted the same pentapeptide extension of RANK that causes expansile skeletal hyperphosphatasia (84dup15). Single nucleotide polymorphisms in TNFRSF11A and TNFRSF11B possibly impacted her phenotype. Our findings: i) reveal that JPD can be associated with an activating mutation within TNFRSF11A, ii) expand the range and overlap of phenotypes among the Mendelian disorders of RANK activation, and iii) call for mutation analysis to improve diagnosis, prognostication, recurrence risk assessment, and perhaps treatment selection among the monogenic disorders of RANKL/OPG/RANK activation.

Genetics of Paget's disease of bone

Paget's disease of bone (PDB) is a common condition, which is characterised by focal areas of increased and disorganized bone remodeling. Genetic factors play an important role in the disease. In some cases, Paget's disease is inherited in an autosomal dominant manner and the most common cause for this is a mutation in the SQSTM1 gene. Other familial cases have been linked to the OPTN locus on Chromosome 10p13 and still other variants have been identified by genome wide association studies that lie within or close to genes that play roles in osteoclast differentiation and function. Mutations in TNFRSF11A, TNFRSF11B and VCP have been identified in rare syndromes with PDB-like features. These advances have improved understanding of bone biology and the causes of PDB. The identification of genetic markers for PDB also raises the prospect that genetic profiling could identify patients at high risk of developing complications, permitting enhanced surveillance and early therapeutic intervention.

RANK rs1805034 T>C polymorphism is associated with susceptibility of esophageal cancer in a Chinese population

Esophageal cancer remains the sixth leading cause of cancer associated death and eighth most common cancer worldwide. Genetic factors, such as single nucleotide polymorphisms (SNPs), may contribute to the carcinogenesis of esophageal cancer. Here, we conducted a hospital based case-control study to evaluate the genetic susceptibility of functional SNPs on the development of esophageal cancer. A total of 629 esophageal squamous cell carcinoma (ESCC) cases and 686 controls were enrolled for this study. The OPG rs3102735 T>C, rs2073618 G>C, RANK rs1805034 T>C, RANKL rs9533156 T>C and rs2277438 A>G were determined by ligation detection reaction method. Our findings suggested that RANK rs1805034 T>C is associated with the susceptibility of ESCC, which is more evident in male and elder (≥63) patients. Our study provides the first evidence that functional polymorphisms RANK rs1805034 T>C may be an indicator for individual susceptibility to ESCC. However, further larger studies among different ethnic populations are warranted to verify our conclusion.

Receptor activator of nuclear factor kappa-B gene polymorphisms in Iranian periodontitis and peri-implantitis patients

PURPOSE

Peri-implantitis and periodontitis are inflammatory and infectious diseases of implant and tooth-supporting tissues. Recently, the role of gene polymorphisms of immune response components in the relevant pathogenesis has been investigated. The present study was the first to evaluate the relationship between two known single nucleotide polymorphisms (SNPs) of the receptor activator of nuclear factor kappa-β (RANK) gene (rs3018362 and rs35211496) in chronic periodontitis and peri-implantitis patients in an Iranian population.

METHODS

Eighty-one periodontally healthy patients, 38 patients with peri-implantitis, and 74 patients with chronic periodontitis were enrolled in this study. DNA was extracted from blood arm vein samples by using Miller's salting out technique according to the manufacturer's instructions given in the extraction kit. The concentration of DNA samples was measured using a spectrophotometer. The genetic polymorphisms of the RANK gene were evaluated using a competitive allele specific polymerase chain reaction (KBioscience allele specific PCR) technique. Differences in the frequencies of genotypes and alleles in the diseased and healthy groups were analyzed using chi-squared statistical tests (P<0.05).

RESULTS

Analysis of rs35211496 revealed statistically significant differences in the expression of the TT, TC, and CC genotypes among the three groups (P=0.00). No statistically significant difference was detected in this respect between the control group and the chronic periodontitis group. The expression of the GG, GA, and AA genotypes and allele frequencies (rs3018362) showed no statistically significant difference among the three groups (P=0.21).

CONCLUSIONS

The results of this study indicate that the CC genotype of the rs35211496 RANK gene polymorphism was significantly associated with peri-implantitis and may be considered a genetic determinant for peri-implantitis, but this needs to be confirmed by further studies in other populations.

Pathobiology of Paget's Disease of Bone

Paget's disease of bone is characterized by highly localized areas of increased bone resorption accompanied by exuberant, but aberrant new bone formation with the primary cellular abnormality in osteoclasts. Paget's disease provides an important paradigm for understanding the molecular mechanisms regulating both osteoclast formation and osteoclast-induced osteoblast activity. Both genetic and environmental etiologies have been implicated in Paget's disease, but their relative contributions are just beginning to be defined. To date, the only gene with mutations in the coding region linked to Paget's disease is sequestosome-1 (SQSTM1), which encodes the p62 protein, and these mutations lead to elevated cytokine activation of NF-B in osteoclasts but do not induce a "pagetic osteoclast" phenotype. Further, genetic mutations linked to Paget's appear insufficient to cause Paget's disease and additional susceptibility loci or environmental factors may be required. Among the environmental factors suggested to induce Paget's disease, chronic measles (MV) infection has been the most studied. Expression of the measles virus nucleocapsid gene (MVNP) in osteoclasts induces pagetic-like osteoclasts and bone lesions in mice. Further, mice expressing both MVNP in osteoclasts and germline mutant p62 develop dramatic pagetic bone lesions that were strikingly similar to those seen in patients with Paget's disease. Thus, interactions between environmental and genetic factors appear important to the development of Paget's disease. In this article we review the mechanisms responsible for the effects of mutant p62 gene expression and MVNP on osteoclast and osteoblast activity, and how they may contribute to the development of Paget's disease of bone.

New insights into the role of sequestosome 1/p62 mutant proteins in the pathogenesis of Paget's disease of bone

Paget's disease of bone (PDB) is characterized by focal areas of aberrant and excessive bone turnover, specifically increased bone resorption and disorganized bone formation. Germline mutations in the sequestosome 1/p62 (SQSTM1/p62) gene are common in PDB patients, with most mutations affecting the ubiquitin-associated domain of the protein. In vitro, osteoclast precursor cells expressing PDB-mutant SQSTM1/p62 protein are associated with increases in nuclear factor κB activation, osteoclast differentiation, and bone resorption. Although the precise mechanisms by which SQSTM1/p62 mutations contribute to disease pathogenesis and progression are not well defined, it is apparent that as well as affecting nuclear factor κB signaling, SQSTM1/p62 is a master regulator of ubiquitinated protein turnover via autophagy and the ubiquitin-proteasome system. Additional roles for SQSTM1/p62 in the oxidative stress-induced Keap1/Nrf2 pathway and in caspase-mediated apoptosis that were recently reported are potentially relevant to the pathogenesis of PDB. Thus, SQSTM1/p62 may serve as a molecular link or switch between autophagy, apoptosis, and cell survival signaling. The purpose of this review is to outline recent advances in understanding of the multiple pathophysiological roles of SQSTM1/p62 protein, with particular emphasis on their relationship to PDB, including challenges associated with translating SQSTM1/p62 research into clinical diagnosis and treatment.

Genetic polymorphism of the OPG gene associated with breast cancer

Background

The receptor activator of NF-κB (RANK), its ligand (RANKL) and osteoprotegerin (OPG) have been reported to play a role in the pathophysiological bone turnover and in the pathogenesis of breast cancer. Based on this we investigated the role of single nucleotide polymorphisms (SNPs) within RANK, RANKL and OPG and their possible association to breast cancer risk.

Methods

Genomic DNA was obtained from Caucasian participants consisting of 307 female breast cancer patients and 396 gender-matched healthy controls. We studied seven SNPs in the genes of OPG (rs3102735, rs2073618), RANK (rs1805034, rs35211496) and RANKL (rs9533156, rs2277438, rs1054016) using TaqMan genotyping assays. Statistical analyses were performed using the χ²-tests for 2 x 2 and 2 x 3 tables.

Results

The allelic frequencies (OR: 1.508 CI: 1.127-2.018, p=0.006) and the genotype distribution (p=0.019) of the OPG SNP rs3102735 differed significantly between breast cancer patients and healthy controls. The minor allele C and the corresponding homo- and heterozygous genotypes are more common in breast cancer patients (minor allele C: 18.4% vs. 13.0%; genotype CC: 3.3% vs. 1.3%; genotype CT: 30.3% vs. 23.5%). No significantly changed risk was detected in the other investigated SNPs. Additional analysis showed significant differences when comparing patients with invasive vs. non-invasive tumors (OPG rs2073618) as well as in terms of tumor localization (RANK rs35211496) and body mass index (RANKL rs9533156 and rs1054016).

Conclusions

This is the first study reporting a significant association of the SNP rs3102735 (OPG) with the susceptibility to develop breast cancer in the Caucasian population.

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.

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.

Paget's disease of bone: an update

PURPOSE OF REVIEW

The review summarizes the recent findings relevant to the clinical management, genetic predisposition, and molecular mechanisms implicated in Paget's disease of bone (PDB).

RECENT FINDINGS

PDB is characterized by focal regions of increased bone remodeling and abnormal bone architecture. PDB is treated effectively with amino-bisphosphonates, which can produce very prolonged disease remission. The disease has a strong genetic component and a large number of studies focus on the cellular mechanisms affected by mutations in the SQSTM1 (sequestosome 1) gene which are associated with PDB. Identifying other genes associated with PDB is an additional active research focus.

SUMMARY

In recent years, there has been a great progress in the understanding of the epidemiology, genetics and molecular biology of PDB. However, an integrative view of the disease cause is still missing and is likely to be attained only with further discoveries of genetic factors, environmental factors, and the interactions between them. Investigations of the cellular mechanisms that are disrupted in PDB contribute greatly to the understanding of normal bone remodeling.

Indications for a genetic association of a VCP polymorphism with the pathogenesis of sporadic Paget's disease of bone, but not for TNFSF11 (RANKL) and IL-6 polymorphisms

Paget's disease of bone (PDB) is, after osteoporosis, the second most common metabolic bone disorder in the elderly Caucasian population. Mutations in the sequestosome 1 gene (SQSTM1) are responsible for the etiology of PDB in a subset of patients, but the disease pathogenesis in the remaining PDB patients is still unknown. Therefore association studies investigating the relationship between genetic polymorphisms and sporadic PDB have been performed in order to find the susceptibility polymorphisms. In this paper, we sought to determine whether polymorphisms in 3 functional candidate genes play a role in the development of sporadic PDB: TNFSF11 (receptor activator of nuclear factor κB ligand, RANKL), VCP (valosin-containing protein) and IL-6 (interleukin 6). Analyzing 9 tag SNPs and 2 multi-marker tests (MMTs) in TNFSF11, 3 tag SNPs and 1 MMT in VCP and 8 tag SNPs in IL-6 in a population of 196 Belgian patients with sporadic PDB and 212 Belgian control individuals revealed that one VCP SNP (rs565070) turned out to be associated with PDB in this Belgian study population (p=5.5×10(-3)). None of the tag SNPs or MMTs selected for TNFSF11 or IL-6 was associated with PDB. Still, replication of our findings in the VCP gene in other populations is important to confirm our results. However, when combining data of VCP with those from other susceptible gene regions from previous association studies (i.e. TNFRSF11A, CSF1, OPTN and TM7SF4), independent effect of each gene region was found and the cumulative population attributable risk is 72.7%.