SNP selection and genotyping Twenty-seven tag SNPs (tSNPs) from five candidate genes (PPARG, CRTAP, TDGF1, PTHR1, and FLNB) in the chromosomal region 3p14-25 were selected for genotyping based on the genotype data obtained from the Han Chinese Seliciclib nmr panel of the phase II HapMap data [39].

The criterion for tagging was set at r2 > 0.8 and minor allele frequency (MAF) > 0.2. The 27 tag SNPs captured 82.4% of common variants in five genes. SNPs rs709157, rs2177153, and rs1131356 showed significant association with BMD in previous studies and are thus, examined in this study. A total of 30 SNPs were genotyped using high-throughput massArray technology. In the genotyping process, 5% of samples were duplicated for quality check, and the reproducibility rate exceeded 99.8%. Mullin et al. recently reported strong associations between rs7646054 in ARHGEF3 and BMD Z-scores at the spine and femoral neck in postmenopausal women [14]. We, thus, also genotyped rs7646054 using the TaqMan Genotyping Assay C__29978110_10 (Applied Biosystems, CA, USA) in our case-control samples. Each reaction contained template

DNA and a final concentration of 1x TaqMan PCR Master Mix, unlabeled forward and reverse primers, VIC, and 6FAM dye-minor groove binder labeled probe for detection of the two alleles. The polymerase chain reaction program was set at 50°C incubation for Vadimezan 2 min followed by 10 min at 92°C. A two-step reaction was repeated with 40 cycles, with denaturation at 92°C for 15 s and annealing and extension at 50°C for 1 min. Subsequent endpoint reading was performed on the PRISM 7000 Sequence Detection System (Applied Biosystems, CA, USA). The reproducibility and the call rate of the TaqMan assay were 100% and 98.7%, respectively. Statistical analysis PLINK, an open source tool set designed for analysis of large data sets in a computationally efficient manner [40], was utilized in quality control filtering, single- and multiple-marker association tests. SNPs missing greater than10%, MAF of less than 1%,

or violating the Hardy–Weinberg Niclosamide equilibrium (HWE) (p < 0.001) were excluded from further analysis. Logistic regression for the additive model, with adjustment for covariates, was applied to test the single-marker genotypic association with BMD at different skeletal sites. The Fisher’s exact test was employed to execute the basic allelic association test. The variable-size sliding window approach was adopted in haplotype analysis as it includes the SNPs that may fall outside predefined linkage disequilibrium (LD) block and thus, enables the full information on genetic variability to be utilized in haplotype analysis [41, 42]. Another advantage of the variable-size sliding window approach is its greater detection power compared with other association-mapping strategies that employ haplotype block or single-SNP locus [41].