Association between two polymorphisms of the bone morpho-genetic protein-2 gene with genetic susceptibility to ossification of the posterior longitudinal ligament of the cervical spine and its severity.

BACKGROUND Ossification of the posterior longitudinal ligament (OPLL) has a strong genetic background. Previous studies have shown that bone morphogenetic protein-2 (BMP2) and BMP2 mRNA are expressed in ossifying matrix and chondrocytes adjacent to cartilaginous areas of OPLL tissues and mesenchymal cells with fibroblastic features in the immediate vicinity of the cartilaginous areas. It is suggested that BMP2 plays different roles in the different stages of development of OPLL. However, it remains unknown which factors induce ligament cells to produce BMP2. METHODS OPLL patients (n = 192) and non-OPLL controls (n = 304) were studied. Radiographs of the cervical spine were analyzed for extent of OPLL. We investigated whether single nucleotide polymorphisms of exons 3 (-726) T/C and 3 (-583) A/G in the BMP2 gene are statistically associated with genetic susceptibility to OPLL in Chinese Han subjects. RESULTS There was no statistical difference between the occurrence of exons 3 (-726) T/C and 3 (-583) A/G and the occurrence of OPLL in the cervical spine. However, there was a significant association between occurrence of exon 3 (-726) T/C polymorphism and occurrence of OPLL in males of cases and controls in the cervical spine. In addition, no significant association was found between the exons 3 (-726) T/C and 3 (-583) A/G with number of ossified cervical vertebrae in OPLL patients. CONCLUSIONS Exon 3 (-583) A/G polymorphism in BMP2 gene is not associated with the occurrence and the extent of OPLL in the cervical spine. Chinese Han male patients with TC and CC genotypes in exon 3 (-726) T/C have genetic susceptibility to OPLL but not to more extensive OPLL in the cervical spine.