Bivariate Genome-Wide Association Study Implicates ATP6V1G1 as a Novel Pleiotropic Locus Underlying Osteoporosis and Age at Menarche

Identification and characterization of the receptors of a microneme adhesive repeat domain of Eimeria maxima microneme protein 3 in chicken intestine epithelial cells

Eimeria maxima microneme protein 3 (EmMIC3) is pivotal in the initial recognition and attachment of E. maxima sporozoites to host cells. EmMIC3 comprises 5 tandem Type I microneme adhesive repeat (MAR) domains, among which MAR2 of EmMIC3 (EmMAR2) has been identified as the primary determinant of EmMIC3-mediated tissue tropism. Nonetheless, the mechanisms through which EmMAR2 guides the parasite to its invasion site through interactions with host receptors remained largely uncharted. In this study, we employed yeast two-hybrid (YTH) screening assays and shotgun LC-MS/MS analysis to identify EmMAR2 receptors in chicken intestine epithelial cells. ATPase H+ transporting V1 subunit G1 (ATP6V1G1), receptor accessory protein 5 (REEP5), transmembrane p24 trafficking protein (TMED2), and delta 4-desaturase sphingolipid 1 (DEGS1) were characterized as the 4 receptors of EmMAR2 by both assays. By blocking the interaction of EmMAR2 with each receptor using specific antibodies, we observed varying levels of inhibition on the invasion of E. maxima sporozoites, and the combined usage of all 4 antibodies resulted in the most pronounced inhibitory effect. Additionally, the spatio-temporal expression profiles of ATP6V1G1, REEP5, TMED2, and DEGS1 were assessed. The tissue-specific expression patterns of EmMAR2 receptors throughout E. maxima infection suggested that ATP6V1G1 and DEGS1 might play a role in early-stage invasion, whereas TMED2 could be involved in middle and late-stage invasion and REEP5 and DEGS1 may participate primarily in late-stage invasion. Consequently, E. maxima may employ a multitude of ligand-receptor interactions to drive invasion during different stages of infection. This study marks the first report of EmMAR2 receptors at the interface between E. maxima and the host, providing insights into the invasion mechanisms of E. maxima and the pathogenesis of coccidiosis.

Twelve Loci Associated With Bone Density in Middle-aged and Elderly Chinese: The Shanghai Changfeng Study

CONTEXT

Previous genome-wide association studies (GWASs) of bone mineral density (BMD) were mainly conducted in Europeans.

OBJECTIVE

To explore genetic variants that affect BMD and sex differences in a Chinese population.

METHODS

A total of 5428 middle-aged and elderly Chinese were included. Dual-energy X-ray absorptiometry was used to measure BMD at the lumbar spine, and total and specific sites of the hip. A mixed linear model was used to analyze the associations between BMD and autosomal genetic variants, adjusting for age, age squared, sex, and menopausal women (model 1); model 2 was further adjusted for height and weight. A GWAS of osteoporosis in the Biobank Japan (BBJ) project was used for replication. GWAMA software was used to detect the statistical significance of sex differences of estimated effects. Gene annotation and pathway enrichment analysis were performed.

RESULTS

Women lost BMD at earlier ages and faster than men. The 2 models identified a total of 12 loci that were associated with BMD at any site. Single nucleotide polymorphisms rs72354346, rs2024219, rs1463093, rs10037512, and rs5880932 were successfully replicated in the BBJ. Variations of rs79262027 G>A (VKORC1L1) and rs4795209 A>G (DDX52) were associated with BMD only in men, and rs1239055408 G>GA (KCNJ2) was associated with BMD only in women. Gene enrichment analysis showed that BMD in a Chinese elderly population was mainly related to ossification, bone resorption, sex hormones, and kidney physiology.

CONCLUSION

The present GWAS identified 12 loci that were significantly associated with BMD at any site in a Chinese population, and 3 of them showed sex differences in their effects.

Regulatory SNP of RREB1 is Associated With Bone Mineral Density in Chinese Postmenopausal Osteoporosis Patients

Postmenopausal osteoporosis (PMO) is the most common bone disorder in elderly Chinese women. Although genetic factors have been shown to have a pivotal role in PMO, studies on genetic loci associated with PMO in Chinese individuals are still lacking. We aimed to identify SNPs that contribute to PMO in Chinese individuals by conducting a genome-wide association study (GWAS). Bone mineral density (BMD) of postmenopausal Chinese women was assessed. Participants with T-score < -2.5 standard deviations (n = 341) were recruited and divided into a discovery group (n = 150) and a replication group (n = 191). GWAS was performed, with T-score as the quantitative trait, using linear regression. Our results revealed that an SNP cluster upstream of RREB1 showed a trend of association with BMD in Chinese PMO patients. The leading SNP of the cluster was rs475011 (p _combined = 1.15 × 10^-6, beta = 0.51), which is a splicing quantitative trait locus (sQTL) of RREB1. This association was further supported by data from the UK Biobank (UKBB; p = 9.56 × 10^-12). The high BMD-associated allele G of rs475011 is related to a high intron excision ratio. This SNP may increase BMD by upregulating mature RREB1 mRNA, based on data from the Genotype-Tissue Expression (GTEx) database. We identified BMD-associated SNPs that regulate RREB1 in Chinese PMO patients. Future functional experiments are needed to further link rs475011, RREB1, and PMO in Chinese individuals.

Searching for female reproductive aging and longevity biomarkers

Female reproductive aging is, in a way, a biological phenomenon that develops along canonical molecular pathways; however, it has particular features. Recent studies revealed complexity of the interconnections between reproductive aging and aging of other systems, and even suggested a cause-effect uncertainty between them. It was also shown that reproductive aging can impact aging processes in an organism at the level of cells, tissues, organs, and systems. Women at the end of their reproductive lives are characterized by the accelerated incidence of age-related diseases. Timing of the onset of menarche and menopause and variability in the duration of reproductive life carry a latent social risk: not having enough information about the reproductive potential, women keep on postponing childbirth. Identification and use of the most accurate and sensitive aging biomarkers enable the prediction of menopause timing and quantification of the true biological and reproductive ages of an organism. We discuss current views on reproductive aging and peculiarities of using available biomarkers of aging. We also consider latest advances in the search for potential genetic markers of reproductive aging. Finally, we posit the importance of determining the female biological age and highlight potential research directions in this area.

Twelve years of GWAS discoveries for osteoporosis and related traits: advances, challenges and applications

Osteoporosis is a common skeletal disease, affecting ~200 million people around the world. As a complex disease, osteoporosis is influenced by many factors, including diet (e.g. calcium and protein intake), physical activity, endocrine status, coexisting diseases and genetic factors. In this review, we first summarize the discovery from genome-wide association studies (GWASs) in the bone field in the last 12 years. To date, GWASs and meta-analyses have discovered hundreds of loci that are associated with bone mineral density (BMD), osteoporosis, and osteoporotic fractures. However, the GWAS approach has sometimes been criticized because of the small effect size of the discovered variants and the mystery of missing heritability, these two questions could be partially explained by the newly raised conceptual models, such as omnigenic model and natural selection. Finally, we introduce the clinical use of GWAS findings in the bone field, such as the identification of causal clinical risk factors, the development of drug targets and disease prediction. Despite the fruitful GWAS discoveries in the bone field, most of these GWAS participants were of European descent, and more genetic studies should be carried out in other ethnic populations to benefit disease prediction in the corresponding population.

Emerging insights on the role of V-ATPase in human diseases: Therapeutic challenges and opportunities

The control of the intracellular pH is vital for the survival of all organisms. Membrane transporters, both at the plasma and intracellular membranes, are key players in maintaining a finely tuned pH balance between intra- and extracellular spaces, and therefore in cellular homeostasis. V-ATPase is a housekeeping ATP-driven proton pump highly conserved among prokaryotes and eukaryotes. This proton pump, which exhibits a complex multisubunit structure based on cell type-specific isoforms, is essential for pH regulation and for a multitude of ubiquitous and specialized functions. Thus, it is not surprising that V-ATPase aberrant overexpression, mislocalization, and mutations in V-ATPase subunit-encoding genes have been associated with several human diseases. However, the ubiquitous expression of this transporter and the high toxicity driven by its off-target inhibition, renders V-ATPase-directed therapies very challenging and increases the need for selective strategies. Here we review emerging evidence linking V-ATPase and both inherited and acquired human diseases, explore the therapeutic challenges and opportunities envisaged from recent data, and advance future research avenues. We highlight the importance of V-ATPases with unique subunit isoform molecular signatures and disease-associated isoforms to design selective V-ATPase-directed therapies. We also discuss the rational design of drug development pipelines and cutting-edge methodological approaches toward V-ATPase-centered drug discovery. Diseases like cancer, osteoporosis, and even fungal infections can benefit from V-ATPase-directed therapies.

Three pleiotropic loci associated with bone mineral density and lean body mass

Both bone mineral density (BMD) and lean body mass (LBM) are important physiological measures with strong genetic determination. Besides, BMD and LBM might have common genetic factors. Aiming to identify pleiotropic genomic loci underlying BMD and LBM, we performed bivariate genome-wide association study meta-analyses of femoral neck bone mineral density and LBM at arms and legs, and replicated in the large-scale UK Biobank cohort sample. Combining the results from discovery meta-analysis and replication sample, we identified three genomic loci at the genome-wide significance level (p < 5.0 × 10-8): 2p23.2 (lead SNP rs4477866, discovery p = 3.47 × 10-8, replication p = 1.03 × 10-4), 16q12.2 (rs1421085, discovery p = 2.04 × 10-9, replication p = 6.47 × 10-14) and 18q21.32 (rs11152213, discovery p = 3.47 × 10-8, replication p = 6.69 × 10-6). Our findings not only provide useful insights into lean mass and bone mass development, but also enhance our understanding of the potential genetic correlation between BMD and LBM.

Comprehensive Genetic Analysis of 128 Candidate Genes in a Cohort With Idiopathic, Severe, or Familial Osteoporosis

Context

The genetic bases of osteoporosis (OP), a disorder with high heritability, are poorly understood at an individual level. Cases of idiopathic or familial OP have long puzzled clinicians as to whether an actionable genetic cause could be identified.

Objective

We performed a genetic analysis of 28 cases of idiopathic, severe, or familial osteoporosis using targeted massively parallel sequencing.

Design

Targeted sequencing of 128 candidate genes was performed using Illumina NextSeq. Variants of interest were confirmed by Sanger sequencing or SNP array.

Patients and Setting

Thirty-seven patients in an academic tertiary hospital participated (54% male; median age, 44 years; 86% with fractures), corresponding to 28 sporadic or familial cases.

Main Outcome Measure

The identification of rare stop-gain, indel, splice site, copy-number, or nonsynonymous variants altering protein function.

Results

Altogether, we identified 28 variants of interest, but only 3 were classified as pathogenic or likely pathogenic variants: COL1A2 p.(Arg708Gln), WNT1 p.(Gly169Asp), and IDUA p.(His82Gln). An association of variants in different genes was found in 21% of cases, including a young woman with severe OP bearing WNT1, PLS3, and NOTCH2 variants. Among genes of uncertain significance analyzed, a potential additional line of evidence has arisen for GWAS candidates GPR68 and NBR1, warranting further studies.

Conclusions

While we hope that continuing efforts to identify genetic predisposition to OP will lead to improved and personalized care in the future, the likelihood of identifying actionable pathogenic variants in intriguing cases of idiopathic or familial osteoporosis is seemingly low.

Genetic Pleiotropy of Bone-Related Phenotypes: Insights from Osteoporosis

PURPOSE OF REVIEW

We summarize recent evidence on the shared genetics within and outside the musculoskeletal system (mostly related to bone density and osteoporosis).

RECENT FINDINGS

Osteoporosis is determined by an interplay between multiple genetic and environmental factors. Significant progress has been made regarding its genetic background revealing a number of robustly validated loci and respective pathways. However, pleiotropic factors affecting bone and other tissues are not well understood. The analytical methods proposed to test for potential associations between genetic variants and multiple phenotypes can be applied to bone-related data. A number of recent genetic studies have shown evidence of pleiotropy between bone density and other different phenotypes (traits, conditions, or diseases), within and outside the musculoskeletal system. Power benefits of combining correlated phenotypes, as well as unbiased discovery, make these studies promising. Studies in humans are supported by evidence from animal models. Drug development and repurposing should benefit from the pleiotropic approach. We believe that future studies should take into account shared genetics between the bone and related traits.

Pleiotropic loci underlying bone mineral density and bone size identified by a bivariate genome-wide association analysis

Aiming to identify pleiotropic genomic loci for bone mineral density and bone size, we performed a bivariate GWAS in five discovery samples and replicated in two large-scale samples. We identified 2 novel loci at 2q37.1 and 6q26. Our findings provide insight into common genetic architecture underlying both traits.

INTRODUCTION

Bone mineral density (BMD) and bone size (BS) are two important factors that contribute to the development of osteoporosis and osteoporotic fracture. Both BMD and BS are highly heritable and they are genetically correlated. In this study, we aim to identify pleiotropic loci associated with BMD and BS.

METHODS

We conducted a bivariate genome-wide association (GWA) analysis of hip BMD and hip BS in 6180 participants from 5 samples, followed by in silico replication in the UK Biobank study of BMD (N = 426,824) and the deCODE study of BS (N = 28,954), respectively.

RESULTS

SNPs from 2 genomic loci were significant at the genome-wide significance (GWS) level (p lt; 5 × 10-8) in the discovery samples and were successfully replicated in the replication samples (2q37.1, lead SNP rs7575512, discovery p = 1.49 × 10-10, replication p = 0.05; 6q26, lead SNP rs1040724, discovery p = 1.95 × 10-8, replication p = 0.03). Functional annotations suggested functional relevance of the identified variants to bone development.

CONCLUSION

Our findings provide insight into the common genetic architecture underlying BMD and BS, and enhance our understanding of the potential mechanism of osteoporosis fracture.

Two novel pleiotropic loci associated with osteoporosis and abdominal obesity

Aiming to uncover a shared genetic basis of abdominal obesity and osteoporosis, we performed a bivariate GWAS meta-analysis of femoral neck BMD (FNK-BMD) and trunk fat mass adjusted by trunk lean mass (TFMadj) in 11,496 subjects from 6 samples, followed by in silico replication in the large-scale UK Biobank (UKB) cohort. A series of functional investigations were conducted on the identified variants. Bivariate GWAS meta-analysis identified two novel pleiotropic loci 12q15 (lead SNP rs73134637, p = 3.45 × 10-7) and 10p14 (lead SNP rs2892347, p = 2.63 × 10-7) that were suggestively associated and that were replicated in the analyses of related traits in the UKB sample (osteoporosis p = 0.06 and 0.02, BMI p = 0.03 and 4.61 × 10-3, N up to 499,520). Cis-eQTL analysis demonstrated that allele C at rs73134637 was positively associated with IFNG expression in whole blood (N = 369, p = 0.04), and allele A at rs11254759 (10p14, p = 9.49 × 10-7) was negatively associated with PRKCQ expression in visceral adipose tissue (N = 313, p = 0.04) and in lymphocytes (N = 117, p = 0.03). As a proof-of-principle experiment, the function of rs11254759, which is 235 kb 5'-upstream from PRKCQ gene, was investigated by the dual-luciferase reporter assay, which clearly showed that the haplotype carrying rs11254759 regulated PRKCQ expression by upregulating PRKCQ promoter activity (p = 4.60 × 10-7) in an allelic specific manner. Mouse model analysis showed that heterozygous PRKCQ deficient mice presented decreased fat mass compared to wild-type control mice (p = 3.30 × 10-3). Mendelian randomization analysis demonstrated that both FNK-BMD and TFMadj were causally associated with fracture risk (p = 1.26 × 10-23 and 1.18 × 10-11). Our findings may provide useful insights into the genetic association between osteoporosis and abdominal obesity.

Association of HIVEP3 Gene and Lnc RNA with Femoral Neck Bone Mineral Content and Hip Geometry by Genome-Wide Association Analysis in Chinese People

PURPOSE

GWAS has successfully located and analyzed the pathogenic genes of osteoporosis. Genetic studies have found that heritability of BMD is 50%-85% while the other half is caused by hip geometric parameters and tissue horizontal characteristics. This study was designed to study the GWAS of osteoporosis in Shanghai Han population.

METHODS

We collected 1224 unrelated healthy young men (20-40 years old), young women (20-40 years old), and postmenopausal women (over 50 years old) who lived in Shanghai. BMD and hip geometric parameters were measured by dual-energy X-ray absorptiometry. The genomic DNA of peripheral blood was extracted and analyzed by using Illumina Human Asian Screening Array-24 + v1.0 (ASA) gene chip. Statistical analysis was carried out to evaluate the relationship between these SNPs and BMD and hip geometric parameters.

RESULTS

A total of 1155 subjects were included. We found that one SNP rs35282355 located in the human immunodeficiency virus type 1 enhancer-binding protein 3 gene (HIVEP3) and another 25 SNPs located in LINC RNA were significantly correlated with bone mineral content (BMC) in the femoral neck (P= 2.30 × 10^-9, P < 5 × 10^-8). We also found that the correlation between SNP rs35282355 and cross-sectional area (CSA) of hip geometry was a significant marginal statistical difference (P = 5.95 × 10^-8).

CONCLUSIONS

Through this study, we found that HIVEP3 gene and LINC RNA are potentially correlated with femoral neck BMC. These results provide important information for us to further understand the etiology and genetic pathogenesis of osteoporosis. In the future, we will expand the sample size to verify these loci and carry out molecular research.

Time since menopause, but not age, is associated with increased risk of osteoporosis

Objectives: This study aimed to determine whether estrogen deficiency is a sole risk factor for osteoporosis or is also associated with age, through indicators such as gender, age, and time since menopause. Methods: A cross-sectional study was conducted evaluating 938 postmenopausal women who underwent bone mineral densitometry. We collected the following data: age, ethnic group, body mass index, smoking, and time since menopause. These data were correlated to the presence of osteoporosis, according to the T-score of the femur and lumbar spine. Results: The prevalence of osteoporosis was 37.8%. Ethnic group (p = 0.47) and smoking habits (p = 0.19) were not associated with osteoporosis. In the group of women with osteoporosis, mean age was significantly higher (p < 0.001), mean body mass index was significantly lower (p < 0.001), and time since menopause was significantly higher (p < 0.001) than in the group of women with no osteoporosis. After multivariate analysis was performed, the only variables that remained independently associated with osteoporosis were body mass index and time since menopause. Higher body mass index was a protective factor (odds ratio = 0.80 [95% confidence interval 0.76; 0.84], p < 0.001). Time since menopause represented a risk factor for osteoporosis (odds ratio = 1.04 [1.02; 1.06], p < 0.001). When divided into categories, the risk increased after 20 years of menopause and gradually every 5 years. Conclusion: Time since menopause and body mass index were the most important factors associated with osteoporosis, confirming that estrogen deficiency, and not age, is the major cause of the disease.

Associations of IDUA and PTCH1 with Bone Mineral Density, Bone Turnover Markers, and Fractures in Chinese Elderly Patients with Osteoporosis

Introduction

Osteoporosis (OP) is a common polygenic disorder in the aging population, and several single nucleotide polymorphisms (SNPs) in the alpha-L-iduronidase (IDUA) gene and patched homolog 1 (PTCH1) gene regulate bone metabolism and affect bone mass. The study aimed at investigating the relationships of rs3755955 and rs6831280 in the IDUA gene and rs28377268 in the PTCH1 gene with bone mineral density (BMD), bone turnover markers (BTMs), and fractures in the elderly Chinese subjects with OP.

Materials and Methods

A cohort of 328 unrelated senile osteoporosis (SOP) patients with or without osteoporotic fractures was recruited. rs3755955, rs6831280, and rs28377268 polymorphisms were identified using SNaPshot technology. BTM levels were determined by electrochemiluminescence (ECL). Bone mineral densities (BMDs) at the lumbar spine (LS) and proximal femur sites were measured by dual-energy X-ray absorptiometry (DEXA) in all subjects. The Hardy-Weinberg equilibrium (HWE) test was performed. HWE P values and comparisons of genotype frequencies were estimated using the chi-square test. Analysis of covariance (ANCOVA) adjusted for confounding factors was performed to investigate associations of SNPs with BMDs and BTMs in subgroups.

Results

The chi-square test indicated that genotype distributions in the control group conformed to HWE (P > 0.05). The distributions of allele and genotype frequencies of rs6831280 between fracture and osteoporotic participants were significantly different (P-allele = 0.002 and P-genotype = 0.012, respectively). Concerning rs6831280, ANCOVA found BMDs at LS 2-4 (L2-4) and total hip (TH) among the study subjects suffering from SOP with GA genotype were lower than in those carrying GG or AA (P-L2-4 = 0.004 and P-TH = 0.027, respectively).

Conclusions

IDUA rs6831280 is associated with BMDs at L2-4 and TH in the elderly Chinese population with SOP and may serve as a marker for the genetic susceptibility to osteoporotic fractures.

Interdisciplinary Work Is Essential for Research on Puberty: Complexity and Dynamism in Action

Puberty is associated with changes in behavior and psychosocial well-being, and is important in lifelong health. We present five different facets regarding interdisciplinary research that are important to puberty. A short history of philosophical issues instrumental in promoting early interdisciplinary research is first presented. We discuss then what is hard and what is easy about interdisciplinary research, the purpose of which is to alert scientists to challenges and opportunities for interdisciplinary research on puberty. Readers then are introduced to advances and obstacles in interdisciplinary research on development. Recommendations for tailoring graduate education toward interdisciplinarity are introduced. Finally, issues related to publication, education of scientists, and policy makers are described. The report concludes with a discussion of funding and policy issues.

Links between age at menarche, antral follicle count, and body mass index in African American and European American women

OBJECTIVE

To examine the relationships between age at menarche, antral follicle count (AFC), and body mass index (BMI) in a multi-ethnic population of women.

DESIGN

Community-based, cross-sectional study.

SETTING

Academic setting.

PATIENT(S)

A total of 245 African American women and 273 European American women, aged 25-45 years, with regular menstrual cycles and no reproductive disorders. The ethnicity of these women was self-reported and genetically validated.

INTERVENTION(S)

The AFCs were measured by transvaginal ultrasound during the early follicular phase. Anthropometric measurements were taken, and age at menarche was gathered by questionnaire.

MAIN OUTCOME MEASURE(S)

Determination of the associations between age of menarche and adult AFC and BMI.

RESULT(S)

Earlier age of menarche was associated with both higher BMIs and higher AFCs in adulthood, with control for female age. The antral follicle difference between early (<12 years) vs. late (≥15 years) initiation of menarche in both white and black women was +3.81 and +3.34 follicles, respectively, which is equivalent to an approximately 20% difference in AFC.

CONCLUSION(S)

This study provides the first evidence that timing of menarche may influence AFC. Because of limited studies on African American women, this work provides additional needed data and may enhance our ability to prospectively screen and better treat various diseases associated with the female reproductive lifespan.

OnPLS-Based Multi-Block Data Integration: A Multivariate Approach to Interrogating Biological Interactions in Asthma

Integration of multiomics data remains a key challenge in fulfilling the potential of comprehensive systems biology. Multiple-block orthogonal projections to latent structures (OnPLS) is a projection method that simultaneously models multiple data matrices, reducing feature space without relying on a priori biological knowledge. In order to improve the interpretability of OnPLS models, the associated multi-block variable influence on orthogonal projections (MB-VIOP) method is used to identify variables with the highest contribution to the model. This study combined OnPLS and MB-VIOP with interactive visualization methods to interrogate an exemplar multiomics study, using a subset of 22 individuals from an asthma cohort. Joint data structure in six data blocks was assessed: transcriptomics; metabolomics; targeted assays for sphingolipids, oxylipins, and fatty acids; and a clinical block including lung function, immune cell differentials, and cytokines. The model identified seven components, two of which had contributions from all blocks (globally joint structure) and five that had contributions from two to five blocks (locally joint structure). Components 1 and 2 were the most informative, identifying differences between healthy controls and asthmatics and a disease–sex interaction, respectively. The interactions between features selected by MB-VIOP were visualized using chord plots, yielding putative novel insights into asthma disease pathogenesis, the effects of asthma treatment, and biological roles of uncharacterized genes. For example, the gene ATP6 V1G1, which has been implicated in osteoporosis, correlated with metabolites that are dysregulated by inhaled corticoid steroids (ICS), providing insight into the mechanisms underlying bone density loss in asthma patients taking ICS. These results show the potential for OnPLS, combined with MB-VIOP variable selection and interaction visualization techniques, to generate hypotheses from multiomics studies and inform biology.

V-ATPases and osteoclasts: ambiguous future of V-ATPases inhibitors in osteoporosis

Vacuolar ATPases (V-ATPases) play a critical role in regulating extracellular acidification of osteoclasts and bone resorption. The deficiencies of subunit a3 and d2 of V-ATPases result in increased bone density in humans and mice. One of the traditional drug design strategies in treating osteoporosis is the use of subunit a3 inhibitor. Recent findings connect subunits H and G1 with decreased bone density. Given the controversial effects of ATPase subunits on bone density, there is a critical need to review the subunits of V-ATPase in osteoclasts and their functions in regulating osteoclasts and bone remodeling. In this review, we comprehensively address the following areas: information about all V-ATPase subunits and their isoforms; summary of V-ATPase subunits associated with human genetic diseases; V-ATPase subunits and osteopetrosis/osteoporosis; screening of all V-ATPase subunits variants in GEFOS data and in-house data; spectrum of V-ATPase subunits during osteoclastogenesis; direct and indirect roles of subunits of V-ATPases in osteoclasts; V-ATPase-associated signaling pathways in osteoclasts; interactions among V-ATPase subunits in osteoclasts; osteoclast-specific V-ATPase inhibitors; perspective of future inhibitors or activators targeting V-ATPase subunits in the treatment of osteoporosis.

Genome-wide association study of lncRNA polymorphisms with bone mineral density

Recent studies suggested that long noncoding RNAs (lncRNAs) were widely transcribed in the genome, but their potential roles in the genetic complexity of human disorders required further exploration. The purpose of the present study was to explore genetic polymorphisms of lncRNAs associated with bone mineral density (BMD) and its potential value. Based on the lncRNASNP database, 55,906 lncSNPs were selected to conduct a genome-wide association study meta-analysis among 11,140 individuals of seven independent studies for BMDs at femoral neck (FN), lumbar spine, and total hip (HIP). Promising results were replicated in Genetic Factors for Osteoporosis Consortium (GEFOS Sequencing, n = 32,965). We found two lncRNA loci that were significantly associated with BMD. MEF2C antisense RNA 1 (MEF2C-AS1) located at 5q14.3 was significantly associated with FN-BMD after Bonferroni correction, and the strongest association signal was detected at rs6894139 (P = 3.03 × 10-9 ). LOC100506136 rs6465531 located at 7q21.3 showed significant association with HIP-BMD (P = 7.43 × 10-7 ). MEF2C-AS1 rs6894139 was replicated in GEFOS Sequencing with P-value of 1.43 × 10-23 . Our results illustrated the important role of polymorphisms in lncRNAs in determining variations of BMD and provided justification and evidence for subsequent functional studies.

Genetics of osteoporosis: searching for candidate genes for bone fragility

The pathogenesis of osteoporosis, a common disease with great morbidity and mortality, comprises environmental and genetic factors. As with other complex disorders, the genetic basis of osteoporosis has been difficult to identify. Nevertheless, several approaches have been undertaken in the past decades in order to identify candidate genes for bone fragility, including the study of rare monogenic syndromes with striking bone phenotypes (e.g. osteogenesis imperfecta and osteopetroses), the analysis of individuals or families with extreme osteoporotic phenotypes (e.g. idiopathic juvenile and pregnancy-related osteoporosis), and, chiefly, genome-wide association studies (GWAS) in large populations. Altogether, these efforts have greatly increased the understanding of molecular mechanisms behind bone remodelling, which has rapidly translated into the development of novel therapeutic strategies, exemplified by the tales of cathepsin K (CTSK) and sclerostin (SOST). Additional biological evidence of involvement in bone physiology still lacks for several candidate genes arisen from GWAS, opening an opportunity for the discovery of new mechanisms regulating bone strength, particularly with the advent of high-throughput genomic technologies. In this review, candidate genes for bone fragility will be presented in comprehensive tables and discussed with regard to how their association with osteoporosis emerged, highlighting key players such as LRP5, WNT1 and PLS3. Current limitations in our understanding of the genetic contribution to osteoporosis, such as yet unidentified genetic modifiers, may be overcome in the near future with better genotypic and phenotypic characterisation of large populations and the detailed study of candidate genes in informative individuals with marked phenotype.

Deficiency of ATP6V1H Causes Bone Loss by Inhibiting Bone Resorption and Bone Formation through the TGF-β1 Pathway

Vacuolar-type H ⁺-ATPase (V-ATPase) is a highly conserved, ancient enzyme that couples the energy of ATP hydrolysis to proton transport across vesicular and plasma membranes of eukaryotic cells. Previously reported mutations of various V-ATPase subunits are associated with increased bone density. We now show that haploinsufficiency for the H subunit of the V₁ domain (ATP6V1H) is associated with osteoporosis in humans and mice. A genome-wide SNP array analysis of 1625 Han Chinese found that 4 of 15 tag SNPs (26.7%) within ATP6V1H were significantly associated with low spine bone mineral density. Atp6v1h^+/- knockout mice generated by the CRISPR/Cas9 technique had decreased bone remodeling and a net bone matrix loss. Atp6v1h^+/- osteoclasts showed impaired bone formation and increased bone resorption. The increased intracellular pH of Atp6v1h^+/- osteoclasts downregulated TGF-β1 activation, thereby reducing induction of osteoblast formation but the bone mineralization was not altered. However, bone formation was reduced more than bone resorption. Our data provide evidence that partial loss of ATP6V1H function results in osteoporosis/osteopenia. We propose that defective osteoclast formation triggers impaired bone formation by altering bone remodeling. In the future, ATP6V1H might, therefore, serve as a target for the therapy of osteoporosis.