T allele at site 6007 of bone morphogenetic protein-4 gene increases genetic susceptibility to ossification of the posterior longitudinal ligament in male Chinese Han population

Background Several candidate genes of ossification of the posterior longitudinal ligament （OPLL） susceptibility have been identified, but their polymorphisms account for only a small percent of the total variance. Bone morphogenetic protein-4 （BMP4） is a potent ectopic ossification inducing factor. BMP4 protein and mRNA are present in cells from OPLL patients, but not non-OPLL controls. A single nucleotide polymorphism of 6007C〉T（rs17563） of BMP4 has been reported to affect bone density in postmenopausal women. Thus, BMP4 may function in OPLL development. Appropriately, the relationship between BMP4 polymorphisms and OPLL was investigated. Methods A case-control association study investigated the genetic etiology in 179 OPLL patients and 298 non-OPLL controls. Extent of OPLL was analyzed by radiologic examinations. Whether single nucleotide polymorphism （SNP） of -5826G〉A（rs1957860） 5＇ of the transcription start site and 6007C〉T（rs17563） in exon 4 of the BMP4 gene were statistically associated with genetic susceptibility to OPLL in Chinese Han subjects was assessed. Results A significant statistical difference in genotype of 6007C〉T polymorphism between male OPLL patients and male controls was evident, and the frequency of ＂TT＂ genotype in male OPLL patients was significantly higher than in male controls （P=0.039）. The frequency of the ＂T＂ allele was also significantly higher in male OPLL subjects than in male controls （P=0.014, OR=1.57）. A significant difference was also observed between the 6007C〉T polymorphism and the number of ossified cervical vertebrae in OPLL patients, while no statistical difference was apparent between the -5826G〉A polymorphism and OPLL occurrence. Conclusions The T allele in the 6007C〉T polymorphism may be a risk factor for male Han Chinese with ossification of the posterior longitudinal ligament in the cervical spine. Chinese Han male patients with CT and TT 6007C〉T genotypes have a genetic susceptibility to OPLL and more extensive OPLL in the cervical spine.