Genetic Variants in Bone Genes

All SNPs with minor allele frequencies (MAF) ≥ 0.01 were searched for between 15 kb upstream and 15 kb downstream of the IBSP and PTHLH genes in the HapMap HCB database by Haploview v4.225 (link). A total of 27 SNPs in the IBSP gene and 24 SNPs in the PTHLH gene were identified. Three additional SNPs in the IBSP gene were included from previous reports17 (link)24 (link). Based on the above criteria, 54 SNPs were included in further analyses (Supplementary Table S1). Peripheral blood was drawn from a vein into a sterile tube containing ethylenediamine tetraacetic acid (EDTA). Genomic DNA was extracted from peripheral blood leukocytes according to the manufacturer’s protocol (Genomic DNA kit, Axygen Scientific Inc., California, USA). DNA was stored at −20 °C for SNP analysis. Genotyping was performed for all SNPs using the MassARRAY platform (Sequenom, San Diego, California, USA). Briefly, SNPs were genotyped using high-throughput, matrix-assisted laser desorption ionization–time-of-flight (MALDI–TOF) mass spectrometry. The resulting spectra were processed using Typer Analyzer software (Sequenom), and genotype data were generated from the samples. As the final genotype call rate of each SNP was greater than 98% and the overall genotyping call rate was 99.6%, the reliability of further statistical analysis was ensured.