Multiple genetic loci from CAST/EiJ chromosome 1 affect vBMD either positively or negatively in a C57BL/6J background

Genetics of aging bone

With aging, the skeleton experiences a number of changes, which include reductions in mass and changes in matrix composition, leading to fragility and ultimately an increase of fracture risk. A number of aspects of bone physiology are controlled by genetic factors, including peak bone mass, bone shape, and composition; however, forward genetic studies in humans have largely concentrated on clinically available measures such as bone mineral density (BMD). Forward genetic studies in rodents have also heavily focused on BMD; however, investigations of direct measures of bone strength, size, and shape have also been conducted. Overwhelmingly, these studies of the genetics of bone strength have identified loci that modulate strength via influencing bone size, and may not impact the matrix material properties of bone. Many of the rodent forward genetic studies lacked sufficient mapping resolution for candidate gene identification; however, newer studies using genetic mapping populations such as Advanced Intercrosses and the Collaborative Cross appear to have overcome this issue and show promise for future studies. The majority of the genetic mapping studies conducted to date have focused on younger animals and thus an understanding of the genetic control of age-related bone loss represents a key gap in knowledge.

Conditional disruption of the prolyl hydroxylase domain-containing protein 2 (Phd2) gene defines its key role in skeletal development

We have previously shown that the increase in osterix (Osx) expression during osteoblast maturation is dependent on the activity of the prolyl hydroxylase domain-containing protein 2 (Phd2), a key regulator of protein levels of the hypoxia-inducible factor family proteins in many tissues. In this study, we generated conditional Phd2 knockout mice (cKO) in osteoblast lineage cells by crossing floxed Phd2 mice with a Col1α2-iCre line to investigate the function of Phd2 in vivo. The cKO mice developed short stature and premature death at 12 to 14 weeks of age. Bone mineral content, bone area, and bone mineral density were decreased in femurs and tibias, but not vertebrae of the cKO mice compared to WT mice. The total volume (TV), bone volume (BV), and bone volume fraction (BV/TV) in the femoral trabecular bones of cKO mice were significantly decreased. Cross-sectional area of the femoral mid-diaphysis was also reduced in the cKO mice. The reduced bone size and trabecular bone volume in the cKO mice were a result of impaired bone formation but not bone resorption as revealed by dynamic histomorphometric analyses. Bone marrow stromal cells derived from cKO mice formed fewer and smaller nodules when cultured with mineralization medium. Quantitative RT-PCR and immunohistochemistry detected reduced expression of Osx, osteocalcin, and bone sialoprotein in cKO bone cells. These data indicate that Phd2 plays an important role in regulating bone formation in part by modulating expression of Osx and bone formation marker genes.

Identification of gender-specific candidate genes that influence bone microarchitecture in chromosome 1

Studies on the identification of the genetic basis for sexual dimorphism in peak bone mass are obviously important for providing novel therapeutic approaches to prevent or treat metabolic bone diseases. Our goal in this study was to identify the bone microstructure that could lead to differences in volumetric bone mineral density (vBMD) and new candidate genes that regulate the gender effect on bone. We used a congenic line of mice that carry the BMD1-4 locus from CAST/EiJ (CAST) mice in a C57BL/6J (B6) background and show greater vBMD in female, but not male, congenics compared to age- and gender-matched B6 mice. To assess the vBMD variations between the two lines of mice, we performed μCT measurements and found no difference in cortical bone volume by tissue volume (BV/TV) between congenics and B6 mice. However, trabecular BV/TV was significantly greater in female, but not male, congenics compared to corresponding B6 mice, which was due to increased trabecular thickness but not reduced trabecular separation, suggesting that bone formation, but not bone resorption, is responsible for the trabecular bone phenotype observed in the female, but not male, congenics. To identify the gender candidate genes, we determined the polymorphisms between B6 and CAST within the BMD1-4 locus and performed gene expression profiling. We identified EF-hand calcium binding domain (Efcab2), consortin, connexin sorting protein (Cnst), and presenilin 2 (Psen2) as potential candidate genes that regulate bone mass by influencing trabecular thickness in a gender-specific manner.

Weak genetic relationship between trabecular bone morphology and obesity in mice

Obesity, in addition to being associated with metabolic diseases, such as diabetes, has also been found to lower the risk of osteoporotic fractures. The relationship between obesity and bone trabecular structure is complex, involving responses to mechanical loading and the effects of adipocyte-derived hormones, both directly interacting with bone tissue and indirectly through central nervous system signaling. Here we examine the effects of sex, a high fat diet, and genetics on the trabecular density and structure of the lumbar and caudal vertebra and the proximal tibia along with body weight, fat pad weight, and serum leptin levels in a murine obesity model, the LGXSM recombinant inbred (RI) mouse strains. The sample included 481 mice from 16 RI strains. We found that vertebral trabecular density was higher in males while the females had higher tibial trabecular density. The high fat diet led to only slightly higher trabecular density in both sexes despite its extreme effects on obesity and serum leptin levels. Trait heritabilities are moderate to strong and genetic correlations among trabecular features are high. Most genetic variation contrasts strains with large numbers of thick, closely-spaced, highly interconnected, plate-like trabeculae with a high bone volume to total volume ratio against strains displaying small numbers of thin, widely-spaced, sparsely connected, rod-like trabeculae with a low bone volume to total volume ratio. Genetic correlations between trabecular and obesity-related traits were low and not statistically significant. We mapped trabecular properties to 20 genomic locations. Only one-quarter of these locations also had effects on obesity. In this population obesity has a relatively minor effect on trabecular bone morphology.

Suggestive linkage to chromosome 1q for bone mineral apparent density in Brazilian sister adolescents

OBJECTIVE

To investigate linkage to chromosome 1q and 11q region for lumbar spine, femoral neck and total body BMD and volumetric BMD in Brazilian sister adolescents aged 10-20-year-old and 57 mothers.

METHODS

We evaluated 161 sister pairs (n=329) aged 10-20 years old and 57 of their mothers in this study. Physical traits and lifestyle factors were collected as covariates for lumbar spine (LS), femoral neck (FN) and total body (TB) BMD and bone mineral apparent density (BMAD). We selected nine microsatellite markers in chromosome 1q region (spanning nearly 33cM) and eight in chromosome 11q region (spanning nearly 34cM) to perform linkage analysis.

RESULTS

The highest LOD score values obtained from our data were in sister pairs LS BMAD analysis. Their values were: 1.32 (P<0.006), 2.61 (P<0.0002) and 2.44 (P<0.0004) in D1S218, D1S2640 and D1S2623 markers, respectively. No significant LOD score was found with LS and FN BMD/BMAD in chromosome 11q region. Only TB BMD showed significant linkage higher than 1.0 for chromosome 11q region in the markers D11S4191 and D11S937.

DISCUSSION/CONCLUSIONS

Our results provided suggestive linkage for LS BMAD at D1S2640 marker in adolescent sister pairs and suggest a possible candidate gene (LHX4) related to adolescent LS BMAD in this region. These results reinforce chromosome 1q21-23 as a candidate region to harbor one or more bone formation/maintenance gene. In the other hand, it did not repeat for chromosome 11q12-13 in our population.

A wild derived quantitative trait locus on mouse chromosome 2 prevents obesity

Background

The genetic architecture of multifactorial traits such as obesity has been poorly understood. Quantitative trait locus (QTL) analysis is widely used to localize loci affecting multifactorial traits on chromosomal regions. However, large confidence intervals and small phenotypic effects of identified QTLs and closely linked loci are impeding the identification of causative genes that underlie the QTLs. Here we developed five subcongenic mouse strains with overlapping and non-overlapping wild-derived genomic regions from an F2 intercross of a previously developed congenic strain, B6.Cg-Pbwg1, and its genetic background strain, C57BL/6J (B6). The subcongenic strains developed were phenotyped on low-fat standard chow and a high-fat diet to fine-map a previously identified obesity QTL. Microarray analysis was performed with Affymetrix GeneChips to search for candidate genes of the QTL.

Results

The obesity QTL was physically mapped to an 8.8-Mb region of mouse chromosome 2. The wild-derived allele significantly decreased white fat pad weight, body weight and serum levels of glucose and triglyceride. It was also resistant to the high-fat diet. Among 29 genes residing within the 8.8-Mb region, Gpd2, Upp2, Acvr1c, March7 and Rbms1 showed great differential expression in livers and/or gonadal fat pads between B6.Cg-Pbwg1 and B6 mice.

Conclusions

The wild-derived QTL allele prevented obesity in both mice fed a low-fat standard diet and mice fed a high-fat diet. This finding will pave the way for identification of causative genes for obesity. A further understanding of this unique QTL effect at genetic and molecular levels may lead to the discovery of new biological and pathologic pathways associated with obesity.

Mouse BMD quantitative trait loci show improved concordance with human genome-wide association loci when recalculated on a new, common mouse genetic map

Bone mineral density (BMD) is a heritable trait, and in mice, over 100 quantitative trait loci (QTLs) have been reported, but candidate genes have been identified for only a small percentage. Persistent errors in the mouse genetic map have negatively affected QTL localization, spurring the development of a new, corrected map. In this study, QTLs for BMD were remapped in 11 archival mouse data sets using this new genetic map. Since these QTLs all were mapped in a comparable way, direct comparisons of QTLs for concordance would be valid. We then compared human genome-wide association study (GWAS) BMD loci with the mouse QTLs. We found that 26 of the 28 human GWAS loci examined were located within the confidence interval of a mouse QTL. Furthermore, 14 of the GWAS loci mapped to within 3 cM of a mouse QTL peak. Lastly, we demonstrated that these newly remapped mouse QTLs can substantiate a candidate gene for a human GWAS locus, for which the peak single-nucleotide polymorphism (SNP) fell in an intergenic region. Specifically, we suggest that MEF2C (human chromosome 5, mouse chromosome 13) should be considered a candidate gene for the genetic regulation of BMD. In conclusion, use of the new mouse genetic map has improved the localization of mouse BMD QTLs, and these remapped QTLs show high concordance with human GWAS loci. We believe that this is an opportune time for a renewed effort by the genetics community to identify the causal variants regulating BMD using a synergistic mouse-human approach.

Genome-wide association study of bone mineral density in premenopausal European-American women and replication in African-American women

CONTEXT

Several genome-wide association studies (GWAS) have been performed to identify genes contributing to bone mineral density (BMD), typically in samples of elderly women and men.

OBJECTIVE

The objective of the study was to identify genes contributing to BMD in premenopausal women.

DESIGN

GWAS using the Illumina 610Quad array in premenopausal European-American (EA) women and replication of the top 50 single-nucleotide polymorphisms (SNPs) for two BMD measures in African-American (AA) women.

SUBJECTS

Subjects included 1524 premenopausal EA women aged 20-45 yr from 762 sibships and 669 AA premenopausal women aged 20-44 yr from 383 sibships.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

BMD was measured at the lumbar spine and femoral neck by dual-energy x-ray absorptiometry. Age- and weight-adjusted BMD values were tested for association with each SNP, with P values determined by permutation.

RESULTS

SNPs in CATSPERB on chromosome 14 provided evidence of association with femoral neck BMD (rs1298989, P = 2.7 x 10(-5); rs1285635, P = 3.0 x 10(-5)) in the EA women, and some supporting evidence was also observed with these SNPs in the AA women (rs1285635, P = 0.003). Genes identified in other BMD GWAS studies, including IBSP and ADAMTS18, were also among the most significant findings in our GWAS.

CONCLUSIONS

Evidence of association to several novel loci was detected in a GWAS of premenopausal EA women, and SNPs in one of these loci also provided supporting evidence in a sample of AA women.

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.

Mouse chromosome 9 quantitative trait loci for soft tissue regeneration: congenic analysis and fine mapping

Development of gene therapies for wound healing will depend on the identification of the genes involved in wound healing and tissue regeneration. Previous quantitative trait loci (QTL) studies in mice using the ear punch model have shown that major QTL exist on chromosome (Chr) 9 for soft tissue regeneration. In this study, we have developed a congenic line that contains the Chr 9 QTL chromosomal region from super healer MRL/MpJ in the genomic background of poor-healing SJL/J. The phenotypic effect of this QTL was confirmed in male mice, where the congenic line has shown significant healing improvement over SJL. Fine mapping of the Chr 9 QTL region with 23 markers at an average distance of 4.2 Mb using a total of 1,564 MRL/MpJ x SJL/J F(2) mice revealed the presence of at least three QTL peaks, implying that three separate loci may contribute to the phenotypic effect of this QTL. Based on the 2-LOD intervals, the total QTL region was confined to a combined length of no more than 28.2 Mb. Application of a Bayesian shrinkage estimation indicated that a major locus was located in a region of just 1.3 Mb.

Integrating global gene expression analysis and genetics

The transcriptome is defined as the collection of all RNAs produced in a cell or tissue at a defined time in development and is one of many stages that make up a biological system. It is also one of the most important; providing the critical link in the flow of information between genes and disease. Therefore, identifying gene expression changes that are reacting to or causing disease promises to significantly enhance our understanding of common disorders. However, only recently has the technology, in the form of DNA microarrays, been in place to quantitate gene expression levels on a genome-wide scale. DNA microarrays are small chips that contain arrays of DNA sequences and are capable of simultaneously quantifying the expression of thousands of genes. When applied to samples representing diseased and normal states, microarray-based expression profiling can identify differentially expressed genes that may play a role in the disease or predict progression or severity. Additionally, the integration of genetics and gene expression promises to aid in uncovering common genetic variations that control a particular disease. In animal models, this approach has already been used to identify genes correlated with disease, prioritized candidates, model causal interactions between genes and traits, and generate gene coexpression networks; all of which have shed light on novel disease mechanisms. In this chapter, we provide an overview of DNA microarray technologies and discuss ways in which microarray expression data can be combined with more traditional experimental approaches to dissect the genetic basis of disease.

Genetic regulation of femoral bone mineral density: complexity of sex effect in chromosome 1 revealed by congenic sublines of mice

The findings that sex-specific effects on femoral structure and peak bone mineral density (BMD) are linked to quantitative trait loci (QTL) provide evidence for the involvement of specific genes that contribute to gender variation in skeletal phenotype. Based on previous findings that the BMD QTL in chromosome 1 (Chr 1) exerts a sex-specific effect on femoral structure, we predicted that congenic sublines of mice that carry one or more of the Chr 1 BMD loci would exhibit gender difference in the volumetric BMD (vBMD) phenotype. To test this hypothesis, we compared skeletal parameters of male and female of five C57BL/6J (B6).CAST/EiJ (CAST)-1 congenic sublines of mice that carry overlapping CAST chromosomal segments from the vBMD loci in Chr 1. Femur vBMD measurements were performed by the peripheral quantitative computed tomography in male and female mice at 16 weeks of age. The skeletal phenotype of the C175-185 and C178-185 congenic sublines of mice provided evidence for the presence of the BMD1-4 locus at 178-180 Mb from the centromere. This QTL affects femur vBMD only in female mice. In contrast, CAST chromosomal region carrying BMD1-1 locus increased femur vBMD both in male and female mice. Furthermore, a gender specific effect on BMD of femur mid-shaft region (mid-BMD) was identified at 168-176 Mb in Chr 1 (F=16.49, P=0.0002), while no significant effect was found on total femur BMD (F=2.67, P=0.11). Moreover, this study allowed us to locate a body weight QTL at 168-172 Mb of Chr 1, the effect of this locus was altered in female mice that carry CAST chromosomal segment 168-176 Mb of Chr 1. Based on this study, we conclude that Chr 1 carries at least two vBMD gender-dependent loci; one genetic locus at 178-180 Mb (BMD1-4 locus) which affects both mid-shaft and total femur vBMD in female mice only, and another gender-dependent locus at 168-176 Mb (BMD1-2 locus) which affects femur mid-shaft vBMD in female but not male mice.

Dissection of a genetically complex cluster of growth and obesity QTLs on mouse chromosome 2 using subcongenic intercrosses

In a previous study we characterized the B6.CAST-(D2Mit329-D2Mit457)N(6) (B62D) congenic strain, which possesses CAST/EiJ (CAST) chromosome 2 donor alleles from 74 to 180 Mbp on a C57BL6/J (B6) background. This strain exhibited significant decreases in body weight and adiposity attributable to the weight gain 2 (Wg2) quantitative trait locus (QTL). To refine the location of Wg2, we used a two-stage genetic dissection strategy consisting of a B62D x B6 backcross, which mapped Wg2 to the proximal portion of the B62D donor region, followed by the development of seven overlapping subcongenic F(2) intercrosses targeting the Wg2 genomic interval. Surprisingly, five of the seven intercrosses displayed significant differences, dependent on genotype, in body weight and/or fat pad mass. These effects were the result of at least four independent QTLs that were named Wg2a, b, c, and d. In contrast to the lean and low body weight phenotype of the B62D parental strain, mice homozygous for CAST congenic alleles (cast/cast) at Wg2a were significantly heavier at 6 and 9 weeks of age, while cast/cast mice at Wg2c had higher levels of total fat. Consistent with the prior observed effects of Wg2, cast/cast mice at Wg2b displayed significant decreases in 6- and 9-week body weight as well as a decrease in total fat pad mass. All of the QTLs had additive effects on body composition except Wg2d, which displayed underdominance for total fat mass. Significant differences in weight and adiposity were also observed in genetically identical b6/b6 homozygous mice across the panel of subcongenics, suggesting either maternal or paternal contributions to body composition. These data represent a significant advancement toward the identification of mouse chromosome 2 growth and obesity quantitative trait genes.

Genetic dissection of mouse distal chromosome 1 reveals three linked BMD QTLs with sex-dependent regulation of bone phenotypes

Genetic analyses with mouse congenic strains for distal Chr1 have identified three closely linked QTLs regulating femoral vBMD, mid-diaphyseal cortical thickness, and trabecular microstructure in a sex-dependent fashion. The homologous relationship between distal mouse Chr 1 and human 1q21-24 offers the possibility of finding common regulatory genes for cortical and trabecular bone.

INTRODUCTION

The distal third of mouse chromosome 1 (Chr 1) has been shown to carry a major quantitative trait locus (QTL) for BMD from several inbred mouse strain crosses. Genetic and functional analyses are essential to identify genes and cellular mechanisms for acquisition of peak bone mass.

MATERIALS AND METHODS

Nested congenic sublines of mice were developed with a C57BL/6J (B6) background carrying <1- to 9-Mbp-sized segments donated from C3H/HeJ (C3H). Isolated femurs from 16-wk-old female and male mice were measured by pQCT and microCT40 for volumetric (v)BMD, mid-diaphyseal cortical thickness, and distal trabecular phenotypes. Static and dynamic histomorphologic data were obtained on selected females and males at 16 wk.

RESULTS AND CONCLUSIONS

We found that the original BMD QTL, Bmd5, mapped to distal Chr 1 consists of three QTLs with different effects on vBMD and trabecular bone in both sexes. Compared with B6 controls, femoral vBMD, BMD, and cortical thickness (p < 0.0001) were significantly increased in congenic subline females, but not in males, carrying C3H alleles at QTL-1. Both females and males carrying C3H alleles at QTL-1 showed marked increases in BV/TV by microCT compared with B6 mice (p < 0.0001). Females increased BV/TV by increasing trabecular thickness, whereas males increased trabecular number. In addition, the microCT40 data showed two unique QTLs for male trabecular bone, QTL-2 and QTL-3, which may interact to regulate trabecular thickness and number. These QTLs are closely linked with and proximal to QTL-1. The histomorphometric data revealed sex-specific differences in cellular and bone formation parameters. Mice and humans share genetic homology between distal mouse Chr 1 and human Chr 1q20-24 that is associated with adult human skeletal regulation. Sex- and compartment-specific regulatory QTLs in the mouse suggest the need to partition human data by sex to improve accuracy of mapping and genetic loci identification.

A genome-wide set of congenic mouse strains derived from CAST/Ei on a C57BL/6 background

We previously reported the construction of two sets of heterozygous congenic strains spanning the mouse genome. For both sets, C57BL/6J was employed as the background strain while DNA from either DBA/2 or CAST/Ei was introgressed to form the congenic region. We have subsequently bred most of these strains to produce homozygous breeding stocks. Here, we report the characterization of the strain set based on CAST/Ei. CAST/Ei is the most genetically distant strain within the Mus mus species and many trait variations relevant to common diseases have been identified in CAST/Ei mice. Despite breeding difficulties for some congenic regions, presumably due to incompatible allelic variations between CAST/Ei and C57BL/6, the resulting congenic strains cover about 80% of the autosomal chromosomes and will be useful as a resource for the further analysis of quantitative trait loci between the strains.

Identification of mouse Duffy antigen receptor for chemokines (Darc) as a BMD QTL gene

It is now well known that bone mineral density (BMD) variance is determined by both genetic and environmental factors. Accordingly, studies in human and animal models have revealed evidence for the presence of several quantitative trait loci (QTL) that contribute to BMD variations. However, the identification of BMD QTL genes remains a big challenge. In the current study, we focused our efforts to identify the BMD candidate gene in chromosome 1 (Chr 1) QTL that was detected from a cross involving high BMD CAST/EiJ (CAST) and low BMD C57BL/6J (B6) mice. To this end, we have combined several approaches including: (1) fine mapping the BMD QTL in Chr 1 of the B6.CAST F2 female mice using a large number of polymorphic markers; (2) the generation of congenic sublines of mice by repeated backcrossing of CAST with B6 mice and phenotype characterization; (3) expression profiling genes in the QTL region; and (4) SNP analyses to identify the mouse Duffy Antigen Receptor for Chemokines (Darc) as a candidate gene for Chr 1 BMD QTL2. We verified the involvement of the Darc protein in BMD variation by evaluating the skeletal phenotype of Darc-knockout mice and congenic sublines of mice carrying small chromosomal segments from CAST BMD QTL. Based on the findings that Darc-antibody blocked formation of multinucleated osteoclasts in vitro and that Darc from CAST binds chemokines, known to regulate osteoclast formation, with reduced affinity compared with Darc from B6 mice, we conclude that Darc regulates BMD negatively by increasing osteoclast formation, and that the genetic association between Darc gene polymorphism and BMD variations in humans merits investigation.

Detecting novel bone density and bone size quantitative trait loci using a cross of MRL/MpJ and CAST/EiJ inbred mice

Most previous studies to identify loci involved in bone mineral density (BMD) regulation have used inbred strains with high and low BMD in generating F(2) mice. However, differences in BMD may not be a requirement in selecting parental strains for BMD quantitative trait loci (QTL) studies. In this study, we intended to identify novel QTL using a cross of two strains, MRL/MpJ (MRL) and CAST/EiJ (CAST), both of which exhibit relatively high BMD when compared to previously used strains. In addition, CAST was genetically distinct. We generated 328 MRL x CAST F(2) mice of both sexes and measured femur BMD and periosteal circumference (PC) using peripheral quantitative computed tomography. Whole-genome genotyping was performed with 86 microsatellite markers. A new BMD QTL on chromosome 10 and another suggestive one on chromosome 15 were identified. A significant femur PC QTL identified on chromosome 9 and a suggestive one on chromosome 2 were similar to those detected in MRL x SJL. QTL were also identified for other femur and forearm bone density and bone size phenotypes, some of which were colocalized within the same chromosomal positions as those for femur BMD and femur PC. This study demonstrates the utility of crosses involving inbred strains of mice which exhibit a similar phenotype in QTL identification.

Confirmation of linkage to chromosome 1q for spine bone mineral density in southern Chinese

Chromosome 1q has previously been linked to bone mineral density (BMD) variation in the general population in several genome-wide linkage studies in both humans and mouse model. The aim of present study is to replicate and fine map the QTL influencing BMD in chromosome 1q in southern Chinese. Twelve microsatellite markers were genotyped for a 57 cMu region in the chromosome 1q in 306 southern Chinese families with 1,459 subjects. Each of these families was ascertained through a proband with BMD Z-scores less than -1.3 at the hip or spine. BMD (g/cm2) at the L1-4 lumbar spine, femoral neck (FN), trochanter and total hip was measured by dual-energy X-ray absortiometry. Linkage analyses were performed using the variance component linkage analysis method implemented in Merlin software. Four markers (D1S2878, D1S196, D1S452, and D1S218) achieved a LOD score greater than 1.0 with spine BMD, with the maximum multipoint LOD score of 2.36 at the marker D1S196. We did not detect a LOD score greater than 1.0 for BMD at the FN, trochanter, or total hip in multipoint linkage analyses. Our results present the first evidence for the presence of an osteoporosis susceptibility gene on chromosome 1q in non-Caucasian subjects. Further analyses of candidate genes are warranted to identify QTL genes and variants underlying the variations of BMD in this region.