Association of ANKH gene polymorphisms with radiographic hand bone size and geometry in a Chuvasha population

Genome-wide association study identifies HMGN3 locus for spine bone size variation in Chinese

Bone size (BS) is one of the major risk factors for osteoporotic fractures. BS variation is genetically determined to a substantial degree with heritability over 50%, but specific genes underlying variation of BS are still largely unknown. To identify specific genes for BS in Chinese, initial genome-wide association scan (GWAS) study and follow-up replication study were performed. In initial GWAS study, a group of 12 contiguous single-nucleotide polymorphism (SNP)s, which span a region of ~25 kb and locate at the upstream of HMGN3 gene (high-mobility group nucleosomal binding domain 3), achieved moderate association signals for spine BS, with P values ranging from 6.2E-05 to 1.8E-06. In the follow-up replication study, eight of the 12 SNPs were detected suggestive replicate associations with BS in 1,728 unrelated female Caucasians, which have well-known differences from Chinese in ethnic genetic background. The SNPs in the region of HMGN3 gene formed a tightly combined haplotype block in both Chinese and Caucasians. The results suggest that the genomic region containing HMGN3 gene may be associated with spine BS in Chinese.

The progressive ankylosis protein regulates cementum apposition and extracellular matrix composition

BACKGROUND/AIMS

Tooth root cementum is sensitive to modulation of inorganic pyrophosphate (PP(i)), an inhibitor of hydroxyapatite precipitation. Factors increasing PP(i) include progressive ankylosis protein (ANK) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) while tissue nonspecific alkaline phosphatase hydrolyzes PP(i). Studies here aimed to define the role of ANK in root and cementum by analyzing tooth development in Ank knock-out (KO) mice versus wild type.

MATERIALS AND METHODS

Periodontal development in KO versus control mice was analyzed by histology, histomorphometry, immunohistochemistry, in situ hybridization, electron microscopy, and nanoindentation. Cementoblast cultures were used in vitro to provide mechanistic underpinnings for PP(i) modulation of cell function.

RESULTS

Over the course of root development, Ank KO cervical cementum became 8- to 12-fold thicker than control cervical cementum. Periodontal ligament width was maintained and other dentoalveolar tissues, including apical cementum, were unaltered. Cervical cementum uncharacteristically included numerous cells, from rapid cementogenesis. Ank KO increased osteopontin and dentin matrix protein 1 gene and protein expression, and markedly increased NPP1 protein expression in cementoblasts but not in other cell types. Conditional ablation of Ank in joints and periodontia confirmed a local role for ANK in cementogenesis. In vitro studies employing cementoblasts indicated that Ank and Enpp1 mRNA levels increased in step with mineral nodule formation, supporting a role for these factors in regulation of cementum matrix mineralization.

CONCLUSION

ANK, by modulating local PP(i), controls cervical cementum apposition and extracellular matrix. Loss of ANK created a local environment conducive to rapid cementogenesis; therefore, approaches modulating PP(i) in periodontal tissues have potential to promote cementum regeneration.

Association of ALPL and ENPP1 gene polymorphisms with bone strength related skeletal traits in a Chuvashian population

Mineralization of the extracellular matrix of bone is an essential element of bone development, maintenance and repair. ALPL and ENPP1 genes and their products are known to be central in local regulation of bone mineralization. The present study investigates potential associations of ENPP1 and ALPL polymorphisms with several phenotypes reflecting bone size and hand BMD. The study sample included 310 Caucasian nuclear families. Forty SNPs in ALPL and 14 SNPs in ENPP1 genetic loci as well as pairwise haplotypes were tested for association with bone strength related traits. Our findings suggest that the region corresponding to exons 7 through 9 of the ALPL gene harbors functional polymorphism affecting both bone size at various skeletal sites (p-value ranged from 0.01 to 0.0001) and hand bone mineral density (p-value=0.0007). The other important finding of consistent association between bone size phenotypes and the 3' untranslated region of ENPP1 gene (p-value ranged from 0.01 to 0.001) imply functional significance of this region to bone growth. The considered anthropometric and radiographic bone phenotypes are closely related to bone fragility thus suggesting a role for both genes in osteoporosis. Further research is required to validate the relevancy of the potentially functional regions identified by our and other studies to normal and pathologic bone development as well as to determine the relevancy of the polymorphisms in ALPL and ENPP1 gene loci to clinical practice.

Morphological and biochemical features of obesity are associated with mineralization genes' polymorphisms

BACKGROUND

Ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) was recently extensively studied as a candidate gene for obesity phenotypes. As the human homologue of the mouse progressive ankylosis (ANKH) and alkaline phosphatase (ALPL) are known functional partners of ENPP1 in bone mineralization, we hypothesized that these genes may also be jointly involved in determining obesity features.

AIM

To examine the effects of the three genes, possible gene-sex and gene-gene interactions on variability of four obesity phenotypes: the body mass index (BMI), the waist-hip ratio (WHR), the epidermal growth factor receptor (EGFR), and leptin.

SUBJECTS AND METHODS

In all, 962 healthy individuals from 230 families were genotyped for 45 single nucleotide polymorphisms (SNPs). The association analysis was performed using two family based association tests (family based association test and pedigree disequilibrium test). The combined P-values of the two tests were estimated by Monte-Carlo simulations. Relative magnitude of the genetic and familial effects, gene-sex and gene-gene interactions were assessed using variance component models.

RESULTS

Associations were observed between ENPP1 polymorphisms and BMI (P=0.0037) and leptin (P=0.0068). ALPL markers were associated with WHR (P=0.0026) and EGFR (P=0.0001). The ANKH gene was associated with all four studied obesity-related traits (P<0.0184), and its effects were modulated by sex. Gene-gene interactions were not detected.

CONCLUSION

The observed pattern of association signals indicates that ANKH may have a generalized effect on adipose tissue physiology, whereas ENPP1 and ALPL affect distinct obesity features. The joint analysis of related genes and integration of the results obtained by different methods used in this research should benefit other studies of similar design.

Genetics of osteoporosis: accelerating pace in gene identification and validation

Osteoporosis is characterized by low bone mineral density and structural deterioration of bone tissue, leading to an increased risk of fractures. It is the most common metabolic bone disorder worldwide, affecting one in three women and one in eight men over the age of 50. In the past 15 years, a large number of genes have been reported as being associated with osteoporosis. However, only in the past 4 years we have witnessed an accelerated pace in identifying and validating osteoporosis susceptibility loci. This increase in pace is mostly due to large-scale association studies, meta-analyses, and genome-wide association studies of both single nucleotide polymorphisms and copy number variations. A comprehensive review of these developments revealed that, to date, at least 15 genes (VDR, ESR1, ESR2, LRP5, LRP4, SOST, GRP177, OPG, RANK, RANKL, COLIA1, SPP1, ITGA1, SP7, and SOX6) can be reasonably assigned as confirmed osteoporosis susceptibility genes, whereas, another >30 genes are promising candidate genes. Notably, confirmed and promising genes are clustered in three biological pathways, the estrogen endocrine pathway, the Wnt/beta-catenin signaling pathway, and the RANKL/RANK/OPG pathway. New biological pathways will certainly emerge when more osteoporosis genes are identified and validated. These genetic findings may provide new routes toward improved therapeutic and preventive interventions of this complex disease.

Animal models of spondyloarthritis

Animal models are available for the study of several different aspects of spondyloarthritis. The models include naturally occurring spontaneous disorders in primates and rodents, spontaneous disorders in transgenic or gene-deleted rodents and induced disorders in rodents. Areas of investigation to which these models contribute include the role HLA-B27, processes of spinal and peripheral joint inflammation and calcification, immune responses to candidate antigens and the role of TNF.

Anthropometric and bone-related biochemical factors are associated with different haplotypes of ANKH locus

BACKGROUND

The human homologue of the mouse progressive ankylosis (ANKH) gene is one of the key genetic factors involved in bone mineralization. Previous studies have shown that plasma levels of osteoprotegerin (OPG) and parathyroid hormone (PTH) are associated with the distal region of the ANKH gene, whereas skeletal size measurements are associated with the promoter region.

AIM

The present study examines the possible phenotype-haplotype specificity of the associations in these two gene regions.

SUBJECTS AND METHODS

The total sample consists of 1249 healthy individuals (mean age = 47.7, SD = 16.8) from 404 nuclear families. Fifteen interrelated anthropometric measurements were transformed into two principal components, reflecting body size and mass. Those, plus circulating levels of PTH and OPG, were subjected to association analysis, using transmission disequilibrium tests (TDTs) with ANKH gene. From 805 to 1150 individuals per SNP were genotyped.

RESULTS

In the proximal region (rs3006069-rs835154-rs835141), associations were found between the A-A-C haplotype and the first principal component reflecting body size (p < or = 0.048), whereas another haplotype, G-G-C, was associated with the first principal component, reflecting the body mass (p < or = 0.008). In the distal region of ANKH (rs39968-rs696294-rs875525), the A-A-C haplotype was found to be associated with OPG plasma levels (p < or = 0.001), whereas the G-A-C haplotype was associated with PTH circulating concentrations (p < or = 0.025).

CONCLUSION

Taken together, the results show discrimination between the corresponding regions and haplotypes, suggesting trait-specific gene variants that influenced bone-related phenotypic variation in the studied population.

Family-based association study of polymorphisms in the RUNX2 locus with hand bone length and hand BMD

Osteoporosis is characterized by reduced bone strength. Bone size and bone mineral density (BMD) are major bone strength determinants. Identification of genes affecting the variability of these traits should improve prognosis and management of osteoporosis. This research was aimed to test the hypothesis of association of radiographic hand bone length (BL) and BMD with polymorphisms in the RUNX2 locus. Four SNPs linked to the two RUNX2 promoters were genotyped in 212 nuclear Caucasian families. These SNPs and four pairwise haplotypes were tested for association with eight BL and BMD traits, adjusted for covariates. We observed significant associations between polymorphisms linked to the RUNX2 P1 promoter and BL mean values for three studied bone groups: all 18 bones, proximal and medial bones (p = 0.0118, 0.0085, and 0.0056, respectively). Mean BMD values for all 18 bones, proximal and medial bones were associated with polymorphisms linked to the RUNX2 P2 promoter (p = 0.0032, 0.0077, 0.0007, respectively). Associations with BL and BMD mean values for medial and proximal bones remained significant even after correction for multiple testing. This study provides evidence of the association between polymorphisms linked to the two RUNX2 promoters and variability of hand BL and BMD. The results suggest independent roles for the two RUNX2 promoters in the determination of the traits studied.

Family-based association study of ROR2 polymorphisms with an array of radiographic hand bone strength phenotypes

For the first time the study provides evidence of association of radiographic hand bone length (BL) and bone mineral density (BMD) with polymorphisms in ROR2 gene that plays important role in skeletal development. This contributes to better understanding of bone physiology and may have application in clinical practice.

INTRODUCTION AND HYPOTHESIS

Bone size and bone mineral density (BMD) are major determinants of bone strength. Identification of genes affecting these traits' variability is important for better understanding of normal and pathological bone physiology and identification of the individuals at risk for bone fracture. This study tested the hypothesis of association of radiographic hand bone length (BL) and BMD with polymorphisms in ROR2 gene that is important in skeletal development.

METHODS

Nineteen ROR2 SNPs were genotyped in 705 individuals, belonging to 212 nuclear families. The four tagging SNPs (tSNPs) and the pairwise haplotypes between adjacent tSNPs were tested for association with series of hand BL and BMD measurements, adjusted for covariates, using family-based association tests.

RESULTS

We observed significant associations with BL and BMD mean values for all 18 studied hand bones (p = 0.0080, 0.0030), mean BL and BMD for proximal phalanges (p = 0.0218, 0.0060) and metacarpal bones (p = 0.0014, 0.0004). In the latter, the association remained significant after correction for multiple testing.

CONCLUSIONS

The region of the first through the second ROR2 introns is most likely to contain the functional polymorphism/s responsible for the observed associations. Further studies are required to identify the ROR2 functional polymorphism/s affecting bone size and BMD variation.

Bivariate linkage study of proximal hip geometry and body size indices: the Framingham study

Femoral geometry and body size are both characterized by substantial heritability. The purpose of this study was to discern whether hip geometry and body size (height and body mass index, BMI) share quantitative trait loci (QTL). Dual-energy X-ray absorptiometric scans of the proximal femur from 1,473 members in 323 pedigrees (ages 31-96 years) from the Framingham Osteoporosis Study were studied. We measured femoral neck length, neck-shaft angle, subperiosteal width (outer diameter), cross-sectional bone area, and section modulus, at the narrowest section of the femoral neck (NN), intertrochanteric (IT), and femoral shaft (S) regions. In variance component analyses, genetic correlations (rho ( G )) between hip geometry traits and height ranged 0.30-0.59 and between hip geometry and BMI ranged 0.11-0.47. In a genomewide linkage scan with 636 markers, we obtained nominally suggestive linkages (bivariate LOD scores > or =1.9) for geometric traits and either height or BMI at several chromosomes (4, 6, 9, 15, and 21). Two loci, on chr. 2 (80 cM, BMI/shaft section modulus) and chr. X (height/shaft outer diameter), yielded bivariate LOD scores > or =3.0; although these loci were linked in univariate analyses with a geometric trait, neither was linked with either height or BMI. In conclusion, substantial genetic correlations were found between the femoral geometric traits, height and BMI. Linkage signals from bivariate linkage analyses of bone geometric indices and body size were similar to those obtained in univariate linkage analyses of femoral geometric traits, suggesting that most of the detected QTL primarily influence geometry of the hip.

Contribution of the putative genetic factors and ANKH gene polymorphisms to variation of circulating calciotropic molecules, PTH and BGP

It is well known that regulation of calcium homeostasis in bone remodeling is one of the most crucial factors for maintaining healthy bones. Parathyroid hormone (PTH) is probably the most important hormone that participates in the bone remodeling process. Another important biochemical factor governing bone metabolism is osteocalcin (BGP). Although the physiological functions of both of these factors are well known, there is still very little known regarding their specific genetic determination and in particular, the specific genes that may regulate the circulating concentrations of these substances. In the present study, we examined whether nine single nucleotide polymorphisms (SNPs) in the human homologue of the mouse progressive ankylosis gene (ANKH)-one of the key genetic factors involved in bone mineralization-can be associated with PTH and BGP levels in apparently healthy human populations. The study sample comprised 244 nuclear families (840 individuals). After adjustment of BGP and PTH for the significant covariates (sex, age and BMI), the contribution of the putative genetic effects was statistically significant (P < 0.001) for both biochemical factors: 45.27 +/- 10.8% for PTH and 30.19 +/- 12.6% for BGP. Application of transmission disequilibrium tests (TDTs) revealed a significant association (P < 0.05) between PTH and two SNPs: rs39968 and rs875525. However, the association became particularly significant for four TDTs (P-values ranging from 0.0025 to 0.0008) when the association with the haplotypes generated from the above SNP was tested. This association remained significant even after correction for multiple testing with a false discovery rate of 0.05.

Genetics and experimental models of crystal-induced arthritis. Lessons learned from mice and men: is it crystal clear?

PURPOSE OF REVIEW

We examine the major genes in mice and humans involved in the pathogenesis of monosodium urate, calcium pyrophosphate dihydrate and hydroxyapatite crystal-induced arthritis.

RECENT FINDINGS

Several genetic causes of renal disease associated with hyperuricemia and gout provide insight into genes involved in renal urate handling. Mutations or polymorphisms in exons 4 and 5 and intron 4 of urate transporter 1 may be independent genetic markers of hyperuricemia and gout. Genetic analysis supports the role of ANKH mutations in calcium pyrophosphate dihydrate-induced arthritis. ANKH gain-of-function mutations were confirmed by functional studies; however, the crystals formed in ATD5 cells were basic calcium phosphate, not calcium pyrophosphate dihydrate, underlying the significance of chondrocyte differentiation state and the factors regulating normal and pathological mineralization. Animal models have implicated a general model of crystal-induced inflammation involving innate immunity through the NALP3 (Natch domain, leucine-rich repeat, and PYD-containing protein 3) inflammasome signaling through the interleukin-1 receptor and its signaling protein myeloid differentiation primary response protein 88.

SUMMARY

Genetic analysis has elucidated genes responsible for crystal formation and animal models have unveiled mechanisms in the development of crystal-induced arthritis. Future studies will hasten understanding of the pathology of crystal-induced arthritis and provide new therapies.

Biochemical and genetic analysis of ANK in arthritis and bone disease

Mutations in the progressive ankylosis gene (Ank/ANKH) cause surprisingly different skeletal phenotypes in mice and humans. In mice, recessive loss-of-function mutations cause arthritis, ectopic crystal formation, and joint fusion throughout the body. In humans, some dominant mutations cause chondrocalcinosis, an adult-onset disease characterized by the deposition of ectopic joint crystals. Other dominant mutations cause craniometaphyseal dysplasia, a childhood disease characterized by sclerosis of the skull and abnormal modeling of the long bones, with little or no joint pathology. Ank encodes a multiple-pass transmembrane protein that regulates pyrophosphate levels inside and outside tissue culture cells in vitro, but its mechanism of action is not yet clear, and conflicting models have been proposed to explain the effects of the human mutations. Here, we test wild-type and mutant forms of ANK for radiolabeled pyrophosphate-transport activity in frog oocytes. We also reconstruct two human mutations in a bacterial artificial chromosome and test them in transgenic mice for rescue of the Ank null phenotype and for induction of new skeletal phenotypes. Wild-type ANK stimulates saturable transport of pyrophosphate ions across the plasma membrane, with half maximal rates attained at physiological levels of pyrophosphate. Chondrocalcinosis mutations retain apparently wild-type transport activity and can rescue the joint-fusion phenotype of Ank null mice. Craniometaphyseal dysplasia mutations do not transport pyrophosphate and cannot rescue the defects of Ank null mice. Furthermore, microcomputed tomography revealed previously unappreciated phenotypes in Ank null mice that are reminiscent of craniometaphyseal dysplasia. The combination of biochemical and genetic analyses presented here provides insight into how mutations in ANKH cause human skeletal disease.

Osteoprotegerin plasma levels are strongly associated with polymorphisms in human homologue of the mouse progressive ankylosis (ANKH) gene

Osteoprotegerin inhibits osteoclastogenesis and plays an important role in the control of bone resorption. However, the genetic mechanisms underlying regulation of OPG levels are currently not fully elucidated. The aim of the present study was to determine whether the ANKH gene, which plays a central role in bone mineralization, contributes to the genetic regulation of OPG levels. A family-based association study used a sample of 159 ethnically homogeneous nuclear families, comprising 556 apparently healthy individuals. Statistical analyses included family aggregation analysis of OPG variation and four types of transmission disequilibrium tests. Each individual was genotyped for 11 SNPs in the ANKH gene. Four TDTs consistently showed a highly significant association between OPG levels and the intronic SNP rs875525 located between exons 6 and 7. The combined p-value for four tests to reject the null hypothesis of no association was 0.0003. Furthermore, haplotypes generated between rs875525 and two additional neighbouring SNPs (rs2291943 and rs2288474) also revealed a significant association with OPG plasma levels (p < 10(-4)-10(-3)). ANKH genetic polymorphisms in the area between SNP rs2291943 and rs2288474 are strongly associated with OPG plasma levels. The molecular mechanism underlying this association is not obvious, and therefore these results should be regarded cautiously until they are confirmed in independent studies.

Physiologic and pathologic functions of the NPP nucleotide pyrophosphatase/phosphodiesterase family focusing on NPP1 in calcification

The catabolism of ATP and other nucleotides participates partly in the important function of nucleotide salvage by activated cells and also in removal or de novo generation of compounds including ATP, ADP, and adenosine that stimulate purinergic signaling. Seven nucleotide pyrophosphatase/phosphodiesterase NPP family members have been identified to date. These isoenzymes, related by up conservation of catalytic domains and certain other modular domains, exert generally non-redundant functions via distinctions in substrates and/or cellular localization. But they share the capacity to hydrolyze phosphodiester or pyrophosphate bonds, though generally acting on distinct substrates that include nucleoside triphosphates, lysophospholipids and choline phosphate esters. PP_i generation from nucleoside triphosphates, catalyzed by NPP1 in tissues including cartilage, bone, and artery media smooth muscle cells, supports normal tissue extracellular PP_i levels. Balance in PP_i generation relative to PP_i degradation by pyrophosphatases holds extracellular PP_i levels in check. Moreover, physiologic levels of extracellular PP_i suppress hydroxyapatite crystal growth, but concurrently providing a reservoir for generation of pro-mineralizing P_i. Extracellular PP_i levels must be supported by cells in mineralization-competent tissues to prevent pathologic calcification. This support mechanism becomes dysregulated in aging cartilage, where extracellular PP_i excess, mediated in part by upregulated NPP1 expression stimulates calcification. PP_i generated by NPP1modulates not only hydroxyapatite crystal growth but also chondrogenesis and expression of the mineralization regulator osteopontin. This review pays particular attention to the role of NPP1-catalyzed PP_i generation in the pathogenesis of certain disorders associated with pathologic calcification.

Strong association between polymorphisms in ANKH locus and skeletal size traits

Loss of bone strength is the main determinant of bone fragility. Bone strength is directly dependent on bone size (BS). A substantial portion of BS variation is attributable to genetic effects. However, the list of genes and allelic variants involved in the determination of BS variation is far from being complete. Polymorphisms in the ANKH gene have been shown to be associated with radiographic hand BS-related phenotypes. The present study examined the possible association of the ANKH gene with skeletal size and shape in order to test the universality of the ANKH effect on BS traits. Our sample consisted of a total of 212 ethnically homogeneous nuclear families (743 individuals) of European origin. Each individual was measured for body height, weight, and several other anthropometrical measurements, and genotyped for nine polymorphic markers (the average heterozygosity level was 0.4). We observed significant associations with practically all the anthropometrical phenotypes studied. More specifically, we found associations with body weight and height, limb length (P</=0.001; promoter region). After adjustment for body height, we demonstrated the substantial association increase for biacromial breadth (P=0.0012; some 140 kb downstream from ANKH) and vertebral column length (P=0.0008; exons 2-7 region). The majority of the observed associations persisted even after correction for multiple testing. For the first time the reliable evidence in support of universality of ANKH gene polymorphisms effect on bone size was provided.

The association between morbidity and radiographic hand osteoarthritis: a population-based study

OBJECTIVES

Osteoarthritis is the most common form of joint disease and is considered to be a risk factor for other morbidities. We performed a population-based study to evaluate the association between morbidity and radiographic hand osteoarthritis.

METHODS

Our population consisted of Chuvashians residing in peripheral villages of the Russian Federation. The investigated cohort included 434 males aged 18-86 years and 385 females aged 18-84 years. Osteoarthritis development was evaluated using the Kellgren and Lawrence grading scheme. Morbidity data was attained from their medical records and divided into 14 categories by an experienced research physician. To explore the relationship between morbidity and age-adjusted radiographic hand osteoarthritis score, one-way analysis of variance was used, with hand osteoarthritis score as a dependent variable and individuals affected vs. non-affected with the specific disease as an independent (grouping) variable.

RESULTS AND CONCLUSIONS

Statistically significant evidence linking radiographic hand osteoarthritis and morbidities was found in patients with ischemic heart disease and gastrointestinal diseases. Our research indicates that individuals with ischemic heart disease have higher values of radiographic hand osteoarthritis, compared to lower values in individuals with gastrointestinal diseases. Additional research is needed to understand the biological mechanisms of the association between morbidity and osteoarthritis.

Variation in femoral length is associated with polymorphisms in RUNX2 gene

INTRODUCTION

Bone size is an important determinant of bone strength. Although it is well established that bone size traits are under the strong genetic control, genes involved in their determination are poorly characterized. The major objective of the present study was to test hypothesis of possible association between three RUNX2 SNP polymorphisms (rs2819858, rs1406846, rs2819854) and anthropometrical femoral length (FEML). In addition, the possibility of association between anthropometrical tibial length (TIBL) and stature and chosen RUNX2 polymorphisms was tested.

MATERIALS AND METHODS

The study was conducted on 265 nuclear families comprised of a total of 904 individuals. DNA samples were available for 705 individuals, belonging to 212 nuclear families. Three different transmission disequilibrium tests (TDTs), population-based and pedigree-based (PDT) association analyses were implemented in order to test the working hypothesis.

RESULTS

The results unambiguously and consistently demonstrated significant association for FEML regardless of the specific polymorphism tested and type of analysis implemented. The P values obtained by TDTs ranged between 0.0155 and 0.0007. The effect of RUNX2 polymorphisms was estimated to explain 1.9% of the total FEML variation after adjustment for sex and age. The data suggested that the strength of association between RUNX2 polymorphisms and FEML may be higher in females (P = 0.007) than in males (P = 0.046), according to PDT. Conversely, no reliable evidence of association between RUNX2 polymorphisms and either TIBL or stature was found.

CONCLUSIONS

For the first time, the evidence of association between RUNX2 polymorphisms and FEML was provided. The results of the present research contribute to the deeper understanding of the genetic architecture of femoral size and introduce the issues of site and sex dependency of the extent of RUNX2 effect. Further studies are required to confirm our findings, specifically focused on clinically oriented sites of skeleton, like femoral neck.

Genetic epidemiology of skeletal system aging in apparently healthy human population

The study of our team was driven by a clinical problem of age-dependent chronic degenerative disease of skeleton that includes osteoporosis (OP) and osteoarthritis (OA)-related phenotypes. The major aims of the study included evaluation of the putative genetic factors determining the rate and pattern of the bone and cartilage loss and identification of the specific genes involved in this process. In addition, we examined genetic effects on circulating molecular factors involved in bone and cartilage metabolism. The skeletal phenotypes were assessed from hand radiographs, in total on about 1200 individuals belonging to ethnically homogeneous nuclear and complex three-generational pedigrees of European origin. The results obtained until now can be divided into three sections: (1) genetic analysis of bone mass/size/geometry characteristics (OP) and traits related to hand OA; (2) pedigree-based investigation of circulating levels of calciotropic hormones, growth factors, cytokines, and biochemical indices of bone and cartilage remodelling; (3) linkage and linkage disequilibrium study of several candidate genes, such as estrogen receptor alpha, collagen type I alpha 1, genes related to extracellular inorganic pyrophosphate transport and OP/OA phenotypes, including biochemical variables. The study provides compelling evidence to suggest strong involvement of the genetic factors in determination of variation of the majority of the examined OP- and OA-related phenotypes.