Association of CA Repeat Polymorphism in Estrogen Receptor β Gene with Postmenopausal Osteoporosis in Chinese

Association of RANKL and OPG Gene Polymorphism in Arab Women with and without Osteoporosis

Receptor activator of the nuclear factor-κB ligand (RANKL) and osteoprotegerin genes (OPG) were identified as susceptible loci for postmenopausal osteoporosis (PMO) in various ethnicities, but neither have been studied in an Arabian population. Hence, the current study aimed to fill this gap. A total of 372 postmenopausal women (174 osteoporosis (OP) and 198 control group (CTRs)) were genotyped for four SNPs: rs2277438A/G and rs9533156T/C (RANKL), and rs2073618C/G and rs3102735T/C (OPG). Anthropometrics, bone mineral density, 25(OH)D and several other bone markers were measured. The frequency distribution of the heterozygous CG genotype of rs2073618 (OPG) was lower in the OP (36.8%) than in CTRs (47%) (OR: 0.6, 95% CI: 0.3–0.97; p = 0.041). No differences in the allelic/genotypic frequencies were detected between the two groups for all other studied SNPs. However, the heterozygous TC genotype of rs3102735 (OPG) was associated significantly with lower BMD at the femoral neck in OP subjects (p = 0.04). The homozygous rare CC genotype of rs9533156 (RANKL) was associated with lower 25(OH)D levels in CTRs (p = 0.032). In contrast, heterozygous AG genotype of rs2277438 (RANKL) is associated with lower 25(OH)D in the OP group (p = 0.02). Our results suggest that RANKL SNPs may impact 25(OH)D levels and that OPG SNP rs2073618A/G is a significant genetic risk factor for PMO Saudi Arabian women.

No Interaction Effect between Interleukin-6 Polymorphisms and Acid Ash Diet with Bone Resorption Marker in Postmenopausal Women

Background: Evidence is growing that a high-acid diet might accelerate the rate of bone loss, and gene polymorphisms such as Interleukin 6 (IL6) -174G/C and -572G/C are related to bone deterioration. However, no study of the interaction between diet and IL6 polymorphisms has been conducted among Asians. Thus, the objective of this study was to determine whether IL6 gene polymorphisms modified the association between dietary acidity and the rate of bone resorption. Methods: This cross-sectional study recruited 203 postmenopausal women (age ranged from 51 to 85 years old) in community settings. The dietary intakes of the participants were assessed using a validated interviewer-administered semi-quantitative food frequency questionnaire (FFQ), while dietary acid load (DAL) was estimated using net endogenous acid production (NEAP). Agena^® MassARRAY genotyping analysis and serum collagen type 1 cross-linked C-telopeptide (CTX1) were used to identify the IL6 genotype and as a bone resorption marker, respectively. The interactions between diet and single-nucleotide polymorphisms (SNPs) were assessed using linear regressions. Results: A total of 203 healthy postmenopausal women aged between 51 and 85 years participated in this study. The mean BMI of the participants was 24.3 kg/m². In IL6 -174 G/C, all the participants carried the GG genotype, while the C allele was absent. Approximately 40% of the participants had a high dietary acid load. Dietary acid load (B = 0.15, p = 0.031) and the IL6 -572 CC genotype group (B = 0.14, p = 0.044) were positively associated with a higher bone resorption. However, there was no moderating effect of the IL6 genetic polymorphism on the relationship between and acid ash diet and bone resorption markers among the postmenopausal women (p = 0.79). Conclusion: High consumption of an acid ash diet and the IL6 -572 C allele seem to attribute to high bone resorption among postmenopausal women. However, our finding does not support the interaction effect of dietary acidity and IL6 (-174G/C and -572G/C) polymorphisms on the rate of bone resorption. Taken together, these results have given scientific research other candidate genes to focus on which may interact with DAL on bone resorption, to enhance planning for preventing or delaying the onset of osteoporosis among postmenopausal women.

Construction of an miRNA-Regulated Pathway Network Reveals Candidate Biomarkers for Postmenopausal Osteoporosis

We aimed to identify risk pathways for postmenopausal osteoporosis (PMOP) via establishing an microRNAs- (miRNA-) regulated pathway network (MRPN). Firstly, we identified differential pathways through calculating gene- and pathway-level statistics based on the accumulated normal samples using the individual pathway aberrance score (iPAS). Significant pathways based on differentially expressed genes (DEGs) using DAVID were extracted, followed by identifying the common pathways between iPAS and DAVID methods. Next, miRNAs prediction was implemented via calculating TargetScore values with precomputed input (log fold change (FC), TargetScan context score (TSCS), and probabilities of conserved targeting (PCT)). An MRPN construction was constructed using the common genes in the common pathways and the predicted miRNAs. Using false discovery rate (FDR) < 0.05, 279 differential pathways were identified. Using the criteria of FDR < 0.05 and |log⁡FC| ≥ 2, 39 DEGs were retrieved, and these DEGs were enriched in 64 significant pathways identified by DAVID. Overall, 27 pathways were the common ones between two methods. Importantly, MAPK signaling pathway and PI3K-Akt signaling pathway were the first and second significantly enriched ones, respectively. These 27 common pathways separated PMOP from controls with the accuracy of 0.912. MAPK signaling pathway and PI3K/Akt signaling pathway might play crucial roles in PMOP.

Identifying dysregulated pathways in postmenopausal osteoporosis through investigation of crosstalk between pathways

The present study aimed to identify potential dysregulated pathways to further reveal the molecular mechanisms of postmenopausal osteoporosis (PMOP) based on pathway‑interaction network (PIN) analysis, which considers crosstalk between pathways. Protein‑protein interaction (PPI) data and pathway information were derived from STRING and Reactome Pathway databases, respectively. According to the gene expression profiles, pathway data and PPI information, a PIN was constructed with each node representing a biological pathway. Principal component analysis was used to compute the pathway activity for each pathway, and the seed pathway was selected. Subsequently, dysregulated pathways were extracted from the PIN based on the seed pathway and the increased classification accuracy, which was measured using the area under the curve (AUC) index according to 5‑fold cross validation. A PIN comprising 2,725 interactions was constructed, which was used to detect dysregulated pathways. Notably, the 'mitotic prometaphase' pathway was selected and defined as a seed pathway. Starting with the seed pathway, network‑based analysis successfully identified one pathway set for PMOP comprising eight dysregulated pathways (such as mitotic prometaphase, resolution of sister chromatid cohesion, mRNA splicing and mRNA splicing‑major) with an AUC score of 0.85, which may provide potential biomarkers for targeted therapy for PMOP.

Identification of crucial genes related to postmenopausal osteoporosis using gene expression profiling

BACKGROUND

Postmenopausal osteoporosis is a common bone disease and characterized by low bone mineral density.

AIM

This study aimed to reveal key genes associated with postmenopausal osteoporosis (PMO), and provide a theoretical basis for subsequent experiments.

METHODS

The dataset GSE7429 was obtained from Gene Expression Omnibus. A total of 20 B cell samples (ten ones, respectively from postmenopausal women with low or high bone mineral density (BMD) were included in this dataset. Following screening of differentially expressed genes (DEGs), coexpression analysis of all genes was performed, and key genes in the coexpression network were screened using the random walk algorithm. Afterwards, functional and pathway analyses were conducted. Additionally, protein-protein interactions (PPIs) between DEGs and key genes were analyzed.

RESULTS

A set of 308 DEGs (170 up-regulated ones and 138 down-regulated ones) between low BMD and high BMD samples were identified, and 101 key genes in the coexpression network were screened out. In the coexpression network, some genes had a higher score and degree, such as CSTA. The key genes in the coexpression network were mainly enriched in GO terms of the defense response (e.g., SERPINA1 and CST3), immune response (e.g., IL32 and CLEC7A); while, the DEGs were mainly enriched in structural constituent of cytoskeleton (e.g., CYLC2 and TUBA1B) and membrane-enclosed lumen (e.g., CCNE1 and INTS5). In the PPI network, CCNE1 interacted with REL; and TUBA1B interacted with ESR1.

CONCLUSIONS

A series of interactions, such as CSTA/TYROBP, CCNE1/REL and TUBA1B/ESR1 might play pivotal roles in the occurrence and development of PMO.

Evaluation of common variants in CNR2 gene for bone mineral density and osteoporosis susceptibility in postmenopausal women of Han Chinese

Postmenopausal osteoporosis is a major health problem with important genetic factors in postmenopausal women. We thoroughly evaluated the relationship of CNR2 polymorphisms with osteoporosis in a cohort of 1032 osteoporosis patients and 2089 healthy controls from Han Chinese postmenopausal women. Statistically significant differences, depending on different genotypes, were presented.

INTRODUCTION

Osteoporosis is a major health problem in postmenopausal women, which is a multifactorial disease in which genetic determinants are modulated by hormonal, environmental, and nutritional factors. An important clinical risk factor in the pathogenesis of osteoporosis is the presence of genetic polymorphism in susceptibility genes. The aim of our study was to investigate whether CNR2 gene, which attributes to osteoporosis susceptibility in some populations, is associated with bone mineral density (BMD) or osteoporosis in Han Chinese postmenopausal women.

METHODS

We examine 39 SNPs covering the region of CNR2 gene in 3121 Han Chinese postmenopausal women, consisting of 1032 osteoporosis patients and 2089 healthy controls, to evaluate the association with BMD and osteoporosis.

RESULTS

We found that rs4237 and rs2501431 were significantly associated with BMD and osteoporosis (corrected p = 0.020085 and 0.017199) in our sample, and the TT genotype of rs2501431 and the AA genotype of rs4237 had lower lumbar spine BMD and femoral neck BMD compared with the other genotypes. Additionally, analyses by haplotypes indicated that two haplotype blocks, containing rs4237 and rs2501431 respectively, in the CNR2 gene significantly associated with BMD and osteoporosis (both global permutation p < 0.001), and a risk haplotype (ATTT) in the block of rs3003336-rs2501431-rs2502992-rs2501432 had almost 4-fold increase in the cases.

CONCLUSIONS

Our results provide further supportive evidence for an important role of CNR2 gene in the etiology of osteoporosis and suggest that it may be a genetic risk factor for BMD and osteoporosis in Han Chinese postmenopausal women.

Association of estrogen receptor β and estrogen-related receptor α gene polymorphisms with bone mineral density in postmenopausal women

The aim of the study was to investigate the possible association of AluI and RsaI polymorphisms of estrogen receptor β (ER-β) gene and 23-bp nucleotide repeat polymorphism of estrogen-related receptor α (ERRα) gene with bone mineral density (BMD) in postmenopausal Egyptian women. Two-hundred postmenopausal osteoporotic women as cases and 180 healthy age-matched postmenopausal women as controls were genotyped by PCR fragment length polymorphism for AluI, allele-specific PCR for RsaI, and by sizing of PCR products on agarose gels for ERRα repeats. sRANKL levels were estimated by ELISA. BMD measurements for spine and femoral neck were performed by dual energy X-ray absorptiometry. A significant difference between women with osteoporosis and controls regarding allele and genotype distributions of AluI G/A (OR 2.37, 95 % CI 1.77-3.18 and p < 0.001 for A allele) and ERRα polymorphisms (for the two repeats allele OR 2.08, 95 % CI 1.09-4.00, and p = 0.02). Osteoporotic women with the AluI AA + GA genotype or with the EERα 2,2 genotype had significantly lower BMD than did women with the other genotypes. Moreover, there was a significant increase of the mean values of sRANKL in carriers of AluI A, RsaI A alleles and in patients having 2,2 genotypes of ERRα (p < 0.001, p < 0.001, p = 0.02, respectively). We demonstrated an association of ER-β AluI G/A and ERRα 23-repeats polymorphisms with BMD in postmenopausal Egyptian women. A possible effect of ER-β and ERRα polymorphisms on the levels of sRANKL was estimated.

The influence of vitamin D receptor genetic variants on bone mineral density and osteoporosis in Chinese postmenopausal women

Growing evidence indicates that the vitamin D receptor (VDR) gene is an important candidate gene for influencing the development of osteoporosis. The aim of the study was to evaluate the potential association between genetic variants of VDR gene and bone mineral density (BMD) and osteoporosis in Chinese postmenopausal women. The study included 970 Chinese postmenopausal women at the postmenopausal osteoporosis (482) and healthy controls (488). The BMD of lumbar spine (L_2–4 anterior-posterior view), femoral neck hip, and total hip was evaluated using the Norland XR-46 dual energy X-ray absorptiometry (DEXA). The genotypes of VDR genetic variants were determined by the created restriction site-PCR (CRS-PCR) and confirmed by DNA sequencing methods. Our data indicated that the VDR p.Glicine (Gly)14 alanine (Ala) and p.histidine (His) 305 glutanine (Gln) genetic variants were statistically associated with adjusted femoral neck hip BMD, adjusted lumbar spine BMD, and adjusted total hip BMD (P values < 0.05). Results from this study suggest that the VDR p.Gly14Ala and p.His305Gln genetic variants are significantly associated with BMD decrease in Chinese postmenopausal women and might be used as molecular markers for assessing the risk of BMD and osteoporosis.

Association analysis between g.18873C>T and g.27522G>A genetic polymorphisms of OPG and bone mineral density in Chinese postmenopausal women

Several studies report that the OPG is an important candidate gene in the pathogenesis of osteoporosis. This study aimed to detect the potential association of OPG gene polymorphisms with osteoporosis in postmenopausal women. We recruited 928 subjects containing 463 with primary postmenopausal osteoporosis and 465 healthy volunteers as controls. The BMD of neck hip, lumbar spine (L_2–4), and total hip were assessed by dual-energy X-ray absorptiometry (DEXA). Through the created restriction site-polymerase chain reaction (CRS-PCR), PCR-restriction fragment length polymorphism (PCR-RFLP), and DNA sequencing methods, the g.18873C>T and g.27522G>A have been investigated. As for g.18873C>T, our data indicated that subjects with CC genotype have significantly higher BMD value than those of CT and TT genotypes (all P values < 0.05). As for g.27522G>A, the BMD values of subjects with GG genotype were significantly higher than those of GA and AA genotypes (all P values < 0.05). Our findings suggest that the OPG g.18873C>T and g.27522G>A genetic polymorphisms are associated with the decreased risk for osteoporosis in Chinese postmenopausal women.

Sex steroid actions in male bone

Sex steroids are chief regulators of gender differences in the skeleton, and male gender is one of the strongest protective factors against osteoporotic fractures. This advantage in bone strength relies mainly on greater cortical bone expansion during pubertal peak bone mass acquisition and superior skeletal maintenance during aging. During both these phases, estrogens acting via estrogen receptor-α in osteoblast lineage cells are crucial for male cortical and trabecular bone, as evident from conditional genetic mouse models, epidemiological studies, rare genetic conditions, genome-wide meta-analyses, and recent interventional trials. Genetic mouse models have also demonstrated a direct role for androgens independent of aromatization on trabecular bone via the androgen receptor in osteoblasts and osteocytes, although the target cell for their key effects on periosteal bone formation remains elusive. Low serum estradiol predicts incident fractures, but the highest risk occurs in men with additionally low T and high SHBG. Still, the possible clinical utility of serum sex steroids for fracture prediction is unknown. It is likely that sex steroid actions on male bone metabolism rely also on extraskeletal mechanisms and cross talk with other signaling pathways. We propose that estrogens influence fracture risk in aging men via direct effects on bone, whereas androgens exert an additional antifracture effect mainly via extraskeletal parameters such as muscle mass and propensity to fall. Given the demographic trends of increased longevity and consequent rise of osteoporosis, an increased understanding of how sex steroids influence male bone health remains a high research priority.

The relationship between the g.27450A>T genetic variant of OPG gene and osteoporosis in Chinese postmenopausal women

The objective of this study is to evaluate the relationship between the g.27450A>T genetic variant of osteoprotegerin (OPG) gene and osteoporosis in Chinese postmenopausal women. A total of 886 subjects were enrolled in this study. The femoral neck hip, lumbar spine (L2-4), and total hip bone mineral density (BMD) were detected by dual-energy X-ray absorptiometry (DEXA). The genotyping of the g.27450A>T genetic variant of OPG gene was investigated by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing methods. Significant differences in the femoral neck hip, lumbar spine (L2-4), and total hip BMD among different genotypes were found, and the subjects with AA genotype were significantly higher than those of AT and TT genotypes (P<0.05). The allele-A could be a decreased risk factor for osteoporosis. Results from this study support that the g.27450A>T genetic variant of OPG gene has potential relationship with BMD and osteoporosis in Chinese postmenopausal women.

The relationship between osteoprotegerin gene polymorphisms and bone mineral density in Chinese postmenopausal women

Previous evidence supports that the osteoprotegerin (OPG) gene is one of the most important candidate genes for influencing the pathogenesis of osteoporosis. The objective of this study was to investigate the relationship between OPG gene polymorphisms and osteoporosis in Chinese postmenopausal women. A total of 764 subjects were included in this study. The bone mineral density (BMD) in the lumbar spine (L2-4), neck hip and total hip was determined by dual-energy X-ray absorptiometry (DEXA). The g.19190C>A and g.25602A>G SNPs were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), created restriction site PCR (CRS-PCR) and DNA sequencing methods. As for g.19190C>A, our data suggested that the BMD value of lumbar spine (L2-4), neck hip and total hip for subjects with CC genotype was significantly higher than that of CA and AA genotypes (P<0.05). No significant difference was detected between the association of g.25602A>G genotypes with spine BMD and neck hip BMD, while total hip BMD almost reached the significant level (P=0.063). These findings provide more evidence that the SNPs in OPG gene could affect BMD and osteoporosis, and the allele-A of g.19190C>A and allele-G of g.25602A>G genetic variants are associated with increased risk for osteoporosis in Chinese postmenopausal women.

Association between osteoprotegerin genetic variants and bone mineral density in Chinese women

Osteoprotegerin gene (OPG) is one of the most important candidate genes for osteoporosis. The aim of this study was to assess the association between the single nucleotide polymorphisms (SNPs) of OPG gene and bone mineral density (BMD). A total of 706 Chinese postmenopausal women were enrolled in this study. OPG gene variants were genotyped through created restriction site-polymerase chain reaction (CRS-PCR) and verified using DNA sequencing methods. The lumbar spine (L2-4), total hip and femoral neck were evaluated for BMD. Two genetic variants (g.18910G>A and g.27406C>T) were detected in this study. Our data indicated that the significant differences of spine BMD, neck hip BMD and total hip BMD were detected among different g.27406C>T genotype, subjects with the genotype CC were significantly higher than those of genotype CT and TT. However, the g.18910G>A polymorphism was not significantly associated with spine BMD, neck hip BMD and total hip BMD in the studied subjects. Results from this study indicated that OPG gene variants were associated with BMD in Chinese postmenopausal women. These findings will be useful to analyze the role of OPG gene in osteoporosis in the further studies.

Association between estrogen receptor-β dinucleotide repeat polymorphism and incidence of femoral fracture

Estrogens are thought to play an important role in bone metabolism through estrogen receptors (ER). Dinucleotide (cytosine-adenine, CA) repeat polymorphism in the human ER-β gene (ESR2) has been reported to be associated with bone mineral density. We aimed to further elucidate the importance of this polymorphism in the pathogenesis of osteoporosis by examining its association with the incidence of femoral fracture. Deoxyribonucleic acids extracted from the renal cortex of 1489 consecutive Japanese autopsies (799 male, mean age 79 years, 690 female, mean age 82 years) with complete clinical/pathological data were enrolled in the study. ESR2 CA repeat polymorphism was determined by polymerase chain reaction using fluorescein-labeled primers. The presence or absence of femoral fracture during each subject's lifetime was determined by thorough examination of the clinical record. Incidence of femoral fracture in subjects bearing at least one allele of 20 CA repeats (4/132, 3.0 %) was significantly lower than in those without this allele (127/1357, 9.4 %, P = 0.0098). After adjustments for age and sex, logistic regression analysis revealed that having no allele of 20 CA repeats was an independent risk factor of femoral fracture [adjusted odds ratio (OR) 3.875, 95 % confidence interval (CI) 1.392-10.788, P = 0.0095], which was emphasized among women (adjusted OR 6.360, 95 % CI 1.520-26.618, P = 0.0133). Japanese subjects, especially women, bearing at least one allele of 20 CA repeats in the ESR2 may have a lower risk of femoral fracture than those without it, suggesting this polymorphism plays a role in bone metabolism.

Association between osteoprotegerin genetic variants and osteoporosis in Chinese postmenopausal women

The objective of this study was to evaluate the association of single nucleotide polymorphisms (SNPs) of osteoprotegerin gene (OPG) with bone mineral density (BMD) and osteoporosis. A total of 338 Chinese postmenopausal women with primary osteoporosis and 367 healthy controls were enrolled. The lumbar spine (L₂₋₄), total hip and femoral neck hip of BMD were assessed by dual-energy X-ray absorptiometry (DEXA). OPG genetic variants were genotyped through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), created restriction site-PCR (CRS-PCR) and DNA sequencing methods. In this study, the g.18861A>G and g.25548C>T SNPs were detected and our data suggested that the significant differences of spine BMD, femoral neck hip BMD and total hip BMD were found among different g.18861A>G genotype, subjects with the AA genotype were significantly higher than those of AG and GG genotypes (p < 0.05). The g.25548C>T variant was not significantly associated with spine BMD, femoral neck hip BMD and total hip BMD (p > 0.05), while almost reached at the significant level in total hip BMD (p = 0.061). These findings suggeste that OPG gene variants are related to BMD and osteoporosis in Chinese postmenopausal women.

Estrogen receptor-β gene polymorphism and colorectal cancer risk: effect modified by body mass index and isoflavone intake

Estrogen receptor (ER)-β signaling has generally been implicated in protection against colorectal cancer. The ER-β gene cytosine-adenine (ESR2 CA) repeat polymorphism was reported to be associated with colorectal cancer, although showing contradicting results probably caused by ethnicity or age distribution of the subjects. We investigated the association between this polymorphism and the colorectal cancer risk in a community-based case-control study in Japan (685 cases/778 controls), including only subjects younger than 75. The effect modifications of the body mass index (BMI) and isoflavone intake were also examined. ESR2 CA repeat polymorphism was determined by polymerase chain reaction using fluorescein-labeled primers. CA repeat alleles were classified into short (S) allele (<22 repeats) and long (L) allele (≥ 22 repeats). Subjects were divided into three genotype groups (SS/SL/LL). The risk of colon cancer, but not of rectal cancer, was increased with an increasing number of L alleles among postmenopausal women; age-adjusted odds ratio (OR) for SL and LL genotypes compared with the SS genotype were 1.78 and 2.91, respectively (trend p = 0.002). Increased risks of colon cancer associated with the L allele were more evident among postmenopausal women with low BMI (<25 kg m(-2)) or with high isoflavone intake. Such associations were not observed among men or premenopausal women. Having longer ESR2 CA repeat increases colon cancer risk among postmenopausal women younger than 75, possibly with modification of BMI and isoflavone intake. Aging and estrogenic condition may be important in the colon cancer pathogenesis associated with ESR2 CA repeat polymorphism.

Estrogen receptor-Beta variants are associated with increased risk of Alzheimer's disease in women with down syndrome

BACKGROUND/AIMS

Genetic variants that affect estrogen activity may influence the risk of Alzheimer's disease (AD). We examined the relation of polymorphisms in the gene for the estrogen receptor-beta (ESR2) to the risk of AD in women with Down syndrome.

METHODS

Two hundred and forty-nine women with Down syndrome, 31-70 years of age and nondemented at baseline, were followed at 14- to 18-month intervals for 4 years. Women were genotyped for 13 single-nucleotide polymorphisms (SNPs) in the ESR2 gene, and their association with AD incidence was examined.

RESULTS

Among postmenopausal women, we found a 2-fold increase in the risk of AD for women carrying 1 or 2 copies of the minor allele at 3 SNPs in introns seven (rs17766755) and six (rs4365213 and rs12435857) and 1 SNP in intron eight (rs4986938) of ESR2.

CONCLUSION

These findings support a role for estrogen and its major brain receptors in modulating susceptibility to AD in women.

Molecular genetic studies of gene identification for osteoporosis: the 2009 update

Osteoporosis is a complex human disease that results in increased susceptibility to fragility fractures. It can be phenotypically characterized using several traits, including bone mineral density, bone size, bone strength, and bone turnover markers. The identification of gene variants that contribute to osteoporosis phenotypes, or responses to therapy, can eventually help individualize the prognosis, treatment, and prevention of fractures and their adverse outcomes. Our previously published reviews have comprehensively summarized the progress of molecular genetic studies of gene identification for osteoporosis and have covered the data available to the end of September 2007. This review represents our continuing efforts to summarize the important and representative findings published between October 2007 and November 2009. The topics covered include genetic association and linkage studies in humans, transgenic and knockout mouse models, as well as gene-expression microarray and proteomics studies. Major results are tabulated for comparison and ease of reference. Comments are made on the notable findings and representative studies for their potential influence and implications on our present understanding of the genetics of osteoporosis.

Genotypes and haplotypes of the estrogen receptor genes, but not the retinoblastoma-interacting zinc finger protein 1 gene, are associated with osteoporosis

Osteoporosis is a common age-related disease with a strong genetic influence. Polymorphisms of ESR1 have consistently been shown to be associated with bone mineral density (BMD) and fracture; however, in regulating bone metabolism, ESR1 interacts with both ESR2 and RIZ1. We therefore examined the effects of polymorphisms in the ESR1, ESR2, and RIZ1 genes and their haplotypes on vertebral fractures and BMD in a case-control study comprising 462 osteoporotic patients and 336 controls. In ESR1, we found the variant C allele of the XbaI polymorphism to be associated with decreased risk of vertebral fractures in women (P < 0.01), whereas in men, the T allele seemed protective (P = 0.05). The variant G allele of the PvuII polymorphism decreased the risk of vertebral fractures independently of lumbar spine BMD in women (P = 0.04) but had no effect in men. Haplotype X-P-H (XbaI:C, PvuII:G, and a high number of TA repeats) was associated with decreased risk of vertebral fractures in women (P = 0.04) but not men. In ESR2, the G allele of the AluI polymorphism was associated with increased fracture risk (P = 0.04), and the haplotype that comprises rs1256031:T and AluI:A increased lumbar spine BMD by 0.04 +/- 0.02 g/cm(2) (P < 0.05) and decreased the risk of vertebral fractures (P = 0.04). There was no effect of the RIZ1 polymorphism on BMD or fracture risk and no evidence of interaction between the polymorphisms and haplotypes thereof. We confirm that genetic variants in ESR1 and ESR2, but not RIZ1, are important in osteoporosis. We found no evidence of interaction between polymorphisms, but we found that the effects of genetic variants in ESR1 might be sex dependent.

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.

Association between the estrogen receptor TA polymorphism and Harm avoidance

In the last decade a large number of studies focused on the recognition of gene variants modulating temperamental traits. The gene coding for the estrogen receptor alpha (ESR1) appears to be an interesting candidate and it has been found to be linked to Harm avoidance (HA). The aim of the present study was to investigate whether the ESR1 TA dinucleotide repeat polymorphism is associated with HA temperamental trait in a sample of Caucasian University students. One hundred ninety healthy subjects were genotyped for ESR1 TA dinucleotide repeat polymorphism and were administered the Temperament and Character Inventory (TCI). ESR1 TA repeat lengths were dichotomized into short and long categories. ANOVA was used to examine the influence of ESR1 variants (short/long) on the means of the TCI HA scores. HA was significantly associated with age and gender in our sample, being higher in older and female subjects. In the global sample as well as in men and women separately, individuals carrying the S/S variant showed significantly higher HA scores. Further analysis on the HA subscales revealed that specific differences could exist between men and women. Our results further suggest a possible role of ESR1 variants on HA. Further research is needed to replicate our findings as well as to better explore the neuro-biological mechanisms of the modulation of ESR1 on HA.

Do Genetic Alterations in Sex Steroid Receptors Contribute to Lacrimal Gland Disease in Sjögren's Syndrome?

BACKGROUND: Defects in sex steroid receptors have been linked to the onset, progression and severity, as well as the sex-related prevalence, of a variety of autoimmune disorders, including lupus, rheumatoid arthritis, multiple sclerosis and diabetes. We hypothesize that defects in estrogen receptor alpha (ESR1), estrogen receptor beta (ESR2) and/or the androgen receptor (AR) may also contribute to the development of lacrimal gland autoimmune sequelae in Sjögren's syndrome. To begin to test this hypothesis, we examined whether mutations exist in the coding regions of ESR1, ESR2 and AR transcripts in lacrimal tissues of mouse models of Sjögren's syndrome. METHODS: Lacrimal and submandibular glands were collected from adult MRL/MpJ-Tnfrsf6(lpr), nonobese diabetic and/or BALB/c mice. Tissues were pooled according to sex and experiment and processed for cDNA generation. PCR primers were designed to amplify 566-875 base pair segments of the entire open reading frame of each receptor. Segments were amplified, purified and then sequenced. Receptor sequences were assembled and compared to each other and to known NCBI sequences. RESULTS: Our results show that almost all ESR1, ESR2 and AR sequences in exocrine tissues of male and female autoimmune and non-autoimmune mice were identical to those of NCBI standards. There was a G-->A shift at position 998 of the ESR2 complete coding sequence in all tissue samples when compared to NCBI reference sequence U81451.1, but this polymorphism was not found in other ESR2 reference sequences. CONCLUSIONS: Our findings indicate that defects in the coding region of sex steroid receptors do not contribute to the pathogenesis of lacrimal gland disease in mouse models of Sjögren's syndrome.

[Cloning of gene fragment of estrogen receptor-beta and its expression in mouse embryo]

In order to study the expression and regulation effects of estrogen receptor-beta (ERbeta) in the development of mouse embryo, the primer of ERbeta was designed, the ERbeta fragment was first obtained by RT-PCR and subcloned into plasmids pGEM- 3Z, then the recombinant plasmids were linearized with the restriction enzymes of EcoRand Hind. Using Sp6 and T7 RNA polymerase, the digoxigenin(dig) labeled sense and anti-sense probes were transcriped in vitro, respectively. Then the expression of ERbeta in mouse embryo was examined with the probes by whole-mount in situ hybridization. The results indicated that ERbeta is expressed in the brain, spinal neural tube, genital ridge, pericardium, limb bud and mandibular arch of 10.5 dpc embryo, and is also expressed in the telencephalon, mesencephalon, medulla oblongata, spinal cord and limb bud of 13.5 dpc embryo. These results suggest that ERbeta maybe play a role of regulation in sexual differentiation, primal differentiation of neural tube, further differentiation of three primary cerebral vesicles and spinal cord, generation and differentiation of bone and cartilage of limb bud, development of pericardium and configuration differentiation of mandibular in mouse embryo.