DNA analysis by pulsed field gel electrophoresis for ossification of the posterior longitudinal ligament.

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We attempted to identify the genes responsible for OPLL by means of DNA analysis of the families of patients with this disease. Lymphocytes were collected from a total of 40 members of 10 families for subsequent genetic analysis. Family members who shared a common HLA haplotype with the patient were found to have a high incidence of ossification of the posterior longitudinal ligament by X-ray examination. This finding suggests that some genetic factors, linked to HLA haplotypes, are involved in the onset of OPLL.We attempted to confirm the presence of this gene by searching for polymorphism of restriction fragments in the members of each patient's family, using a large DNA electrophoresis apparatus. This analysis revealed that the siblings who shared a common HLA haplotype with the patient often showed polymorphism of the 2.7 Kb DNA fragment on chromosome 6. We compared polymorphism of the 2.7 KB DNA fragmetn on chromosome 6 between patinets with OPLL and 40 healthy volunteers. This comparison, however, did not resolve the question of whether or not polymorphism of the 2.7 Kb DNA fragment is specific to OPLL patients.We also analyzed the genetic polymorphism of alkaline phosphatase (ALP), bone morphogenic protein (BMP)-2, collagen alpha-2 and tissue necrosing factor (TNF)-alpha. This revealed that the incidence of polymorphism of the gene of collagen alpha-2 differs significantly between the OPLL group and the healthy controls. It is possible that polymorphism of collagen alpha-2 gene is rosponsible for the onset of OPLL.The present stufy was the first DNA analysis of OPLL.We believe this study has served as pioneering work in the study of the etiology of OPLL,using the methods of molecular biology.