Identification of novel RANK polymorphisms and their putative association with low BMD among postmenopausal women

Bone mineral density (BMD) is the major factor for determining bone strength, which is closely correlated to osteoporotic fracture risk and is largely determined by multiple genetic factors. The RANK (TNFRSF11A), receptor for RANKL, is a member of the tumor necrosis factor receptor (TNFR) superfamily and plays a central role in osteoclast development. In order to investigate the effects of RANK polymorphism on BMD and osteoporosis, we directly sequenced the RANK gene in 24 Korean individuals and identified 25 sequence variants. Eleven of these polymorphisms were selected and genotyped in a larger-scale study of postmenopausal women (n = 560). Areal BMD (g/cm(2)) of the anterior-posterior lumbar spine and the nondominant proximal femur were measured using dual-energy X-ray absorptiometry. We found that two intronic polymorphisms in the RANK gene [RANK + 34863G > A (rs12458117) and RANK + 35928insdelC (new polymorphism found in this study) in intron 6] were significantly associated with the BMD of the lumbar spine, i.e., rare alleles were significantly associated with low BMD of the lumbar spine among Korean postmenopausal women (p = 0.04 and 0.02, respectively). These polymorphisms were also associated with low BMD of proximal femur sites, including Ward's triangle, trochanter, and total femur. Our results suggest that +34863G > A and +35928insdelC polymorphisms in RANK are possible genetic factors for low BMD in postmenopausal women.