Polymorphisms in ALOX12, but not ALOX15, are significantly associated with BMD in postmenopausal women

Polymorphisms in inflammation associated genes ALOX15 and IL-6 are associated with bone properties in young women and fracture in elderly

PURPOSE

ALOX12 and ALOX15 encode arachidonate lipoxygenases which produce lipid metabolites involved in inflammatory processes. Metabolites generated by ALOX12 and ALOX15 can activate the expression of the potent pro-inflammatory cytokine IL-6, and produce endogenous ligands for PPARG. In this study, polymorphisms in ALOX12, ALOX15, IL6 and PPARG were investigated for association with bone properties in young and elderly Swedish women.

METHODS

Three SNPs in ALOX12, five in ALOX15, one each in IL6 and PPARG were genotyped in the cohorts PEAK-25 (n=1061 women; all 25y) and OPRA (n=1044 women; all 75y). Bone mineral density (BMD) and quantitative ultrasound (QUS) were analyzed in both cohorts; trabecular bone score (TBS) in PEAK-25; bone loss, fracture incidence and serum C-reactive protein (CRP) were assessed in OPRA.

RESULTS

In the elderly women ALOX15 (rs2619112) was associated with CRP levels (p=0.004) and incident fracture of any type (p=0.014), although not with BMD or ultrasound. In young women, carrying the common T allele (ALOX 15 rs748694) was associated with lower QUS values (p=0.002-0.006). The IL6 SNP was associated with lower BMD in PEAK-25 (femoral neck p=0.034; hip p=0.012). TBS was not associated with variation in any gene. Variants in the ALOX12 and PPARγ were not associated with BMD in either cohort.

CONCLUSIONS

This study suggests that variation in inflammation related genes ALOX15 and IL6 was associated with bone microarchitecture and density in young adult women, but appears to be less important in the elderly, despite an observed association with CRP as a marker of inflammation and incident fracture.

The role of lipoxygenases in pathophysiology; new insights and future perspectives

Lipoxygenases (LOXs) are dioxygenases that catalyze the formation of corresponding hydroperoxides from polyunsaturated fatty acids such as linoleic acid and arachidonic acid. LOX enzymes are expressed in immune, epithelial, and tumor cells that display a variety of physiological functions, including inflammation, skin disorder, and tumorigenesis. In the humans and mice, six LOX isoforms have been known. 15-LOX, a prototypical enzyme originally found in reticulocytes shares the similarity of amino acid sequence as well as the biochemical property to plant LOX enzymes. 15-LOX-2, which is expressed in epithelial cells and leukocytes, has different substrate specificity in the humans and mice, therefore, the role of them in mammals has not been established. 12-LOX is an isoform expressed in epithelial cells and myeloid cells including platelets. Many mutations in this isoform are found in epithelial cancers, suggesting a potential link between 12-LOX and tumorigenesis. 12R-LOX can be found in the epithelial cells of the skin. Defects in this gene result in ichthyosis, a cutaneous disorder characterized by pathophysiologically dried skin due to abnormal loss of water from its epithelial cell layer. Similarly, eLOX-3, which is also expressed in the skin epithelial cells acting downstream 12R-LOX, is another causative factor for ichthyosis. 5-LOX is a distinct isoform playing an important role in asthma and inflammation. This isoform causes the constriction of bronchioles in response to cysteinyl leukotrienes such as LTC4, thus leading to asthma. It also induces neutrophilic inflammation by its recruitment in response to LTB4. Importantly, 5-LOX activity is strictly regulated by 5-LOX activating protein (FLAP) though the distribution of 5-LOX in the nucleus. Currently, pharmacological drugs targeting FLAP are actively developing. This review summarized these functions of LOX enzymes under pathophysiological conditions in mammals.

Genetic variation in the lipoxygenase pathway and risk of colorectal neoplasia

Arachidonate lipoxygenase (ALOX) enzymes metabolize arachidonic acid to generate potent inflammatory mediators and play an important role in inflammation-associated diseases. We investigated associations between colorectal cancer risk and polymorphisms in ALOX5, FLAP, ALOX12, and ALOX15, and their interactions with nonsteroidal anti-inflammatory drug (NSAID) use. We genotyped fifty tagSNPs, one candidate SNP, and two functional promoter variable nucleotide tandem repeat (VNTR) polymorphisms in three US population-based case-control studies of colon cancer (1,424 cases/1,780 controls), rectal cancer (583 cases/775 controls), and colorectal adenomas (485 cases/578 controls). Individuals with variant genotypes of the ALOX5 VNTR had a decreased risk of rectal cancer, with the strongest association seen for individuals with one or more alleles of >5 repeats (wild type = 5, OR>5/≥5 = 0.42, 95% CI 0.20-0.92; P = 0.01). Four SNPs in FLAP (rs17239025), ALOX12 (rs2073438), and ALOX15 (rs4796535 and rs2619112) were associated with rectal cancer risk at P ≤ 0.05. One SNP in FLAP (rs12429692) was associated with adenoma risk. A false discovery rate (FDR) was applied to account for false positives due to multiple testing; the ALOX15 associations were noteworthy at 25% FDR. Colorectal neoplasia risk appeared to be modified by NSAID use in individuals with variant alleles in FLAP and ALOX15. One noteworthy interaction (25% FDR) was observed for rectal cancer. Genetic variability in ALOXs may affect risk of colorectal neoplasia, particularly for rectal cancer. Additionally, genetic variability in FLAP and ALOX15 may modify the protective effect of NSAID use against colorectal neoplasia.

A strategy for promoting bone regeneration by inducible expression of 15-LOX-1

Repairing large bone defects is a major orthopaedic problem, with current treatments being constrained by the regenerative capacity of human tissue. Current methods for repairing bone defects include osteogenesis, osteoconduction, osteoinduction, and tissue engineering; however, the cumulative effect of these methods is, as of yet, rather unsatisfactory. Recent research has demonstrated that knockout of the cell cycle inhibitor p21, which works as a switch to control regenerative capacity, can promote cell proliferation and appendage regeneration. The enzyme 15-lipoxygenase type 1 (15-LOX-1), which is involved in arachidonic and linoleic acid metabolism, has the potential to down-regulate the expression of p21. Therefore, we hypothesise that the construction of a new bone substitute that expresses 15-LOX-1 locally will promote osteoblast proliferation through inhibition of p21, resulting in an effective and inducible method for promoting bone regeneration.

Polymorphisms in the human ALOX12 and ALOX15 genes are associated with peak bone mineral density in Chinese nuclear families

SUMMARY

Association between ten single-nucleotide polymorphisms (SNPs) in the human ALOX12 and ALOX15 genes and variations in peak bone mineral density (BMD) in a large sample of Chinese nuclear families with female offspring using the quantitative transmission disequilibrium test (QTDT). Our results suggest that the genetic polymorphisms in both human ALOX12 and ALOX15 may contribute to variations in the peak BMD of Chinese women.

INTRODUCTION

The aim of this study was to investigate whether polymorphisms in the human ALOX12 and ALOX15 genes are associated with variations in peak BMD in Chinese nuclear families with female offspring.

METHODS

Each five SNPs in the ALOX12 and ALOX15 genes were genotyped in a total of 1,260 individuals from 401 Chinese nuclear families. The BMD of the lumbar spine, femoral neck and total hip was measured by dual-energy X-ray absorptiometry. We tested whether a single SNP or a haplotype was associated with peak BMD variations using the QTDT.

RESULTS

Using QTDT to measure within-family associations in ALOX15, we observed a significant association between rs916055 and BMD in the lumbar spine (p = 0.027 in the permutation 1,000 test). However, in ALOX12, rs312470 was significantly associated with BMD in the femoral neck (p = 0.029 and p = 0.036 in the permutation 1,000 test). The results of a haplotype analysis supported the findings of the single locus test for ALOX15.

CONCLUSIONS

Our results suggest that the genetic polymorphisms in both human ALOX12 and ALOX15 may contribute to variations in the peak BMD of Chinese women.

Genetic influence of candidate osteoporosis genes in saudi arabian population: a pilot study

Background and Objectives. The purpose of the present study is to find the genes and SNP that influence BMD and postmenopausal Saudi women. Material and Methods. Two-hundred ethnic Saudi Arabian women with a diagnosis of postmenopausal osteoporosis were the subjects of this study. Baseline blood hematology, biochemistry, and bone panel were done. Blood was collected, and three TaqMan-MGB probes were used to analyze SNP variants in ALOX15 (rs7220870), LRP5 (C 25752205 10), and TNFRSF11B (C 11869235 10). Results. The variant of ALOX15 17p13 showed that the BMD of the spine was lower in the AA allele (P value <0.002) and fractures were highest at 50% compared to CC allele. In the TNFRSF11B gene, BMD of the hip and spine was significantly higher in the GG allele and the history of fractures was significantly higher in GG group. With regard to the LRP5 (C 25752205 10) gene, there was no significant difference between allele groups. Conclusion(s). This study shows that the genetic influence of osteoporosis in the Caucasian and Saudi Arabians population is similar. We believe that the same genetic markers that influence osteoporosis in the Caucasian race could be used for further studies in the Saudi Arabian population.

Polymorphisms in the ALOX12 gene and osteoporosis

ALOX12 produces ligands for PPARγ thereby turning mesenchymal stem cells into adipocytes instead of osteoblasts. We investigated the effect of polymorphisms in the ALOX12 gene on BMD and fracture risk in two Danish cohorts and found four polymorphisms and a haplotype thereof to be associated with BMD and fracture risk.

INTRODUCTION

Stimulation of the PPARγ with ligands produced by the ALOX enzymes drives mesenchymal stem cells in an adipocyte direction at the expense of osteoblasts leading to decreased osteoblast number and BMD. Previously, polymorphisms in the ALOX12 gene have been associated with osteoporosis.

METHODS

We examined the effect of ALOX12 polymorphisms on BMD and the risk of fractures in two Danish cohorts: AROS, a case-control population comprising 809 individuals and DOPS, a population comprising 1,716 perimenopausal women allocated to hormone therapy or not at baseline and followed for up to 10 years. On the basis of linkage disequilibrium (LD) between SNPs throughout the gene and previous genetic association studies we chose ten polymorphisms for investigation. Genotyping was carried out using the Sequenom MassARRAY genotyping system and TaqMan assays.

RESULTS

In AROS, individuals heterozygous for the polymorphisms rs3840880, rs9897850, rs2292350 and rs1126667 had a 3.0-4.7% decreased lumbar spine BMD (p = 0.02-0.06) and an increased risk of vertebral fractures (p < 0.05) compared with individuals homozygous for either allele. In DOPS, none of the individual SNPs were associated with BMD or incident fractures. In both cohorts, the above-mentioned SNPs comprised an LD-block (pairwise D´ = 1.0, r (2) = 0.45-0.97). A haplotype comprising all the common alleles (frequency 9%) was associated with decreased bone loss at the hip (p < 0.05) and decreased incidence of osteoporotic fractures (p < 0.05) in DOPS and increased femoral neck BMD in AROS (p < 0.05).

CONCLUSION

Our study suggests that genetic variants in ALOX12 may influence BMD and fracture risk.

The genetics of bone loss: challenges and prospects

CONTEXT

A strong genetic influence on bone mineral density has been long established, and modern genotyping technologies have generated a flurry of new discoveries about the genetic determinants of bone mineral density (BMD) measured at a single time point. However, much less is known about the genetics of age-related bone loss. Identifying bone loss-related genes may provide new routes for therapeutic intervention and osteoporosis prevention.

EVIDENCE ACQUISITION

A review of published peer-reviewed literature on the genetics of bone loss was performed. Relevant studies were summarized, most of which were drawn from the period 1990-2010.

EVIDENCE SYNTHESIS

Although bone loss is a challenging phenotype, available evidence supports a substantial genetic contribution. Some of the genes identified from recent genome-wide association studies of cross-sectional BMD are attractive candidate genes for bone loss, most notably genes in the nuclear factor κB and estrogen endocrine pathways. New insights into the biology of skeletal development and regulation of bone turnover have inspired new hypotheses about genetic regulation of bone loss and may provide new directions for identifying genes associated with bone loss.

CONCLUSIONS

Although recent genome-wide association and candidate gene studies have begun to identify genes that influence BMD, efforts to identify susceptibility genes specific for bone loss have proceeded more slowly. Nevertheless, clues are beginning to emerge on where to look, and as population studies accumulate, there is hope that important bone loss susceptibility genes will soon be identified.

Pharmacogenetics of osteoporosis-related bone fractures: moving towards the harmonization and validation of polymorphism diagnostic tools

Osteoporosis is one of the most common skeletal chronic conditions in developed countries, hip fracture being one of its major healthcare outcomes. There is considerable variation in the implementation of current pharmacological treatment and prevention, despite consistent recommendations and guidelines. Many studies have reported conflicting findings of genetic associations with bone density and turnover that might predict fracture risk. Moreover, it is not clear whether genetic differences exist in relation to the morbidity and efficiency of the pharmacotherapy treatments. Clinical response, including beneficial and adverse events associated with osteoporosis treatments, is highly variable among individuals. In this context, the present article intends to summarize putative candidate genes and genome-wide association studies that have been related with BMD and fracture risk, and to draw the attention to the need for pharmacogenetic methodology that could be applicable in clinical translational research after an adequate validation process. This article mainly compiles analysis of important polymorphisms in osteoporosis documented previously, and it describes the simple molecular biology tools for routine genotype acquisition. Validation of methods for the easy, fast and accessible identification of SNPs is necessary for evolving pharmacogenetic diagnostic tools in order to contribute to the discovery of clinically relevant genetic variation with an impact on osteoporosis and its personalized treatment.

ALOX12 polymorphisms are associated with fat mass but not peak bone mineral density in Chinese nuclear families

OBJECTIVE

Arachidonate 12-lipoxygenase (ALOX12) is a member of the lipoxygenase superfamily, which catalyzes the incorporation of molecular oxygen into polyunsaturated fatty acids. The products of ALOX12 reactions serve as endogenous ligands for peroxisome proliferator-activated receptor γ (PPARG). The activation of the PPARG pathway in marrow-derived mesenchymal progenitors stimulates adipogenesis and inhibits osteoblastogenesis. Our objective was to determine whether polymorphisms in the ALOX12 gene were associated with variations in peak bone mineral density (BMD) and obesity phenotypes in young Chinese men.

METHODS

All six tagging single-nucleotide polymorphisms (SNPs) in the ALOX12 gene were genotyped in a total of 1215 subjects from 400 Chinese nuclear families by allele-specific polymerase chain reaction. The BMD at the lumbar spine and hip, total fat mass (TFM) and total lean mass (TLM) were measured using dual-energy X-ray absorptiometry. The pairwise linkage disequilibrium among SNPs was measured, and the haplotype blocks were inferred. Both the individual SNP markers and the haplotypes were tested for an association with the peak BMD, body mass index, TFM, TLM and percentage fat mass (PFM) using the quantitative transmission disequilibrium test (QTDT).

RESULTS

Using the QTDT, significant within-family association was found between the rs2073438 polymorphism in the ALOX12 gene and the TFM and PFM (P=0.007 and 0.012, respectively). Haplotype analyses were combined with our individual SNP results and remained significant even after correction for multiple testing. However, we failed to find significant within-family associations between ALOX12 SNPs and the BMD at any bone site in young Chinese men.

CONCLUSIONS

Our present results suggest that the rs2073438 polymorphism of ALOX12 contributes to the variation of obesity phenotypes in young Chinese men, although we failed to replicate the association with the peak BMD variation in this sample. Further independent studies are needed to confirm our findings.

Genetic determinants of osteoporosis: common bases to cardiovascular diseases?

Osteoporosis is the most common and serious age-related skeletal disorder, characterized by a low bone mass and bone microarchitectural deterioration, with a consequent increase in bone fragility and susceptibility to spontaneous fractures, and it represents a major worldwide health care problem with important implications for health care costs, morbidity and mortality. Today is well accepted that osteoporosis is a multifactorial disorder caused by the interaction between environment and genes that singularly exert modest effects on bone mass and other aspects of bone strength and fracture risk. The individuation of genetic factors responsible for osteoporosis predisposition and development is fundamental for the disease prevention and for the setting of novel therapies, before fracture occurrence. In the last decades the interest of the Scientific Community has been concentrated in the understanding the genetic bases of this disease but with controversial and/or inconclusive results. This review tries to summarize data on the most representative osteoporosis candidate genes. Moreover, since recently osteoporosis and cardiovascular diseases have shown to share common physiopathological mechanisms, this review also provides information on the current understanding of osteoporosis and cardiovascular diseases common genetic bases.

ALOX12 gene is associated with the onset of natural menopause in white women

OBJECTIVE

Natural menopause is a key physiological event in a woman's life. Timing of menopause affects risk for many postmenopausal systemic disorders and may thus influence life expectancy. Age at natural menopause (ANM) is largely determined genetically, but a list of candidate genes is far from complete. This study investigated the ALOX12 gene for its possible association with ANM.

METHODS

Six single-nucleotide polymorphisms (SNPs) of the gene (rs9904779, rs2073438, rs11571340, rs434473, rs2307214, and rs312462) were genotyped in a random sample of 210 unrelated white women. The SNPs and common haplotypes were then analyzed for their association with ANM. Smoking, alcohol consumption, and duration of breast-feeding were used as covariates.

RESULTS

Two SNPs, rs9904779 and rs434473 (encodes a replacement of asparagine by serine in the protein), were significantly associated with ANM (P = 0.022 and 0.033, respectively). The minor alleles of both SNPs seem to promote about 1.3- to 1.5-year earlier menopause and confer a 1.6 to 1.8 times higher risk for early menopause. All SNPs indicated significant or nearly significant interactions with alcohol use and duration of breast-feeding. Five common haplotypes were also associated with ANM.

CONCLUSIONS

The ALOX12 gene seems to be associated with the timing of natural menopause in white women.

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.

How genomics has informed our understanding of the pathogenesis of osteoporosis

Osteoporosis is a skeletal disorder characterized by compromised bone strength that predisposes a person to an increased risk of fracture. Osteoporosis is a complex trait that involves multiple genes, environmental factors, and gene-gene and gene-environment interactions. Twin and family studies have indicated that between 25% and 85% of the variation in bone mass and other skeletal phenotypes is heritable, but our knowledge of the underlying genes is limited. Bone mineral density is the most common assessment for diagnosing osteoporosis and is the most often used quantitative value in the design of genetic studies. In recent years, our understanding of the pathophysiology of osteoporosis has been greatly facilitated by advances brought about by the Human Genome Project. Genetic approaches ranging from family studies of monogenic traits to association studies with candidate genes, to whole-genome scans in both humans and animals have identified a small number of genes that contribute to the heritability of bone mass. Studies with transgenic and knockout mouse models have revealed major new insights into the biology of many of these identified genes, but much more needs to be learned. Ultimately, we hope that by revealing the underlying genetics and biology driving the pathophysiology of osteoporosis, new and effective treatment can be developed to combat and possibly cure this devastating disease. Here we review the rapidly evolving field of the genomics of osteoporosis with a focus on important gene discoveries, new biological/physiological paradigms that are emerging, and many of the unanswered questions and hurdles yet to be overcome in the field.

Quantitative trait loci, genes, and polymorphisms that regulate bone mineral density in mouse

This is an in silico analysis of data available from genome-wide scans. Through analysis of QTL, genes and polymorphisms that regulate BMD, we identified 82 BMD QTL, 191 BMD-associated (BMDA) genes, and 83 genes containing known BMD-associated polymorphisms (BMDAP). The catalogue of all BMDA/BMDAP genes and relevant literatures are provided. In total, there are substantially more BMDA/BMDAP genes in regions of the genome where QTL have been identified than in non-QTL regions. Among 191 BMDA genes and 83 BMDAP genes, 133 and 58 are localized in QTL regions, respectively. The difference was still noticeable for the chromosome distribution of these genes between QTL and non-QTL regions. These results have allowed us to generate an integrative profile of QTL, genes, polymorphisms that determine BMD. These data could facilitate more rapid and comprehensive identification of causal genes underlying the determination of BMD in mouse and provide new insights into how BMD is regulated in humans.

Genetic variation in candidate osteoporosis genes, bone mineral density, and fracture risk: the study of osteoporotic fractures

Candidate osteoporosis gene variants were examined for associations with fracture risk and bone mineral density (BMD). A total of 9,704 white women were recruited at four U.S. clinical centers and enrolled into the Study of Osteoporotic Fractures, a longitudinal cohort study. Genotyping of 31 polymorphisms from 18 candidate osteoporosis genes was performed in 6,752 women. Incident radiographic fractures were identified at the third and eighth examinations compared with the baseline examination. BMD was measured at the total hip by dual-energy X-ray absorptiometry. Analyses were adjusted for age, clinic site, and self-reported ethnicity. During a mean follow-up of 14.5 years, a total of 849 hip, 658 vertebral, and 2,496 nonhip/nonvertebral fractures occurred in 6,752 women. Women carrying the ALOX15_G48924T T/T genotype had a higher rate of hip fracture (hazard ratio [HR] = 1.33;95% confidence interval [95% CI] = 1.00-1.77) compared with the G/G genotype. Compared with those carrying the PRL_T228C T/T genotype, women with either the C/C (HR = 0.80; 95% CI = 0.67-0.95) or C/T (HR = 0.81; 95% CI = 0.68-0.97) genotype had a lower rate of nonvertebral/nonhip fractures. Women carrying the BMP2_A125611G G/G genotype had a higher rate of vertebral fracture (odds ratio [OR] = 1.51; 95% CI = 1.03-2.23) compared with the A/A genotype. Women with the ESR1_C1335G G/G genotype had a higher rate of vertebral fracture (OR = 1.64; 95% CI = 1.07-2.50) compared with the C/C genotype. Compared with those with the MMP2_C595T C/C genotype, women with the C/T (OR = 0.79; 95% CI = 0.65-0.96) or T/T (OR = 0.44; 95% CI = 0.27-0.72) genotype had a lower rate of vertebral fracture. In conclusion, polymorphisms in several candidate genes were associated with hip, vertebral, and nonhip/nonvertebral fractures but not with total hip BMD in this large population based cohort study.

Association studies of ALOX5 and bone mineral density in healthy adults

Animal studies suggest that arachidonate 5-lipoxygenase (encoded by ALOX5) may be a genetic determinant of bone mineral density. We tested this hypothesis in a sample of healthy men and women and did not find consistent evidence for an association between variation in this gene and either lumbar spine or femoral neck BMD.

INTRODUCTION

Phenotypic variation in bone mineral density (BMD) among healthy adults is influenced by both genetic and environmental factors. A recent mouse study implicated ALOX5, which encodes arachidonate 5-lipoxygenase, as a contributing factor to areal BMD (aBMD).

METHODS

Fifteen single nucleotide polymorphisms (SNPs) distributed throughout ALOX5 were genotyped in three healthy groups: 1,688 European American, premenopausal sisters, 512 African American premenopausal sisters and 715 European American brothers. Statistical analyses were performed in the three groups to test for association between these SNPs and femoral neck and lumbar spine aBMD.

RESULTS

Significant (p < or = 0.05) evidence of association was observed with three of the SNPs. However, despite the linkage disequilibrium between SNPs, adjacent SNPs did not provide statistical evidence of association in any of the three study groups.

CONCLUSIONS

These data do not provide consistent evidence of association between genomic variation in ALOX5 and clinical variability in aBMD in healthy subjects.

Molecular genetic studies of gene identification for osteoporosis

This review comprehensively summarizes the most important and representative molecular genetics studies of gene identification for osteoporosis published up to the end of September 2007. It is intended to constitute a sequential update of our previously published reviews covering the available data up to the end of 2004. Evidence from candidate gene-association studies, genome-wide linkage and association studies, as well as functional genomic studies (including gene-expression microarray and proteomics) on osteogenesis and osteoporosis, are reviewed separately. Studies of transgenic and knockout mice models relevant to osteoporosis are summarized. The major results of all studies are tabulated for comparison and ease of reference. Comments are made on the most notable findings and representative studies for their potential influence and implications on our present understanding of genetics of osteoporosis. The format adopted by this review should be ideal for accommodating future new advances and studies.