Polymorphism at an Sp1 binding site of COL1A1 and bone mineral density in premenopausal female twins and elderly fracture patients

Polymorphism at an Sp1 binding site in the COL1A1 gene has been reported to be associated with bone mineral density (BMD) and osteoporotic vertebral f racture. We therefore examined for associations and linkage of the Sp1 poly morphism in the COL1A1 gene and BMD at the lumbar spine and femoral neck in 38 monozygotic (MZ) and 40 dizygotic (DZ) twin pairs of white adult women. All twins were premenopausal with an age range of 21-49 years. Sp1 genotyp es of 56 patients with idiopathic osteoporotic vertebral fracture were exam ined for a preponderance of either genotype relative to our normal healthy twin subjects. In the twin sample no significant association was found betw een Sp1 genotypes and BMD at the spine and femoral neck. No linkage of Sp1 genotype and BMD at the spine or femoral neck was observed in DZ twins disc ordant for genotype. Frequencies of Sp1 genotypes were similar in our healt hy (twin) and fracture population samples. In conclusion, in our American s ample of premenopausal twins we found no association or Linkage of the Sp1 polymorphism at the COL1A1 gene and BMD at the lumbar spine and femoral nec k, and no over-representation of any Sp1 genotype was observed in our sampl e of patients with osteoporotic vertebral fracture. Taken together these re sults indicate that the Sp1 polymorphism is not related to BMD in our Ameri can sample, and contrasts with the findings in a British population.