Association of a T262C transition in exon 1 of estrogen-receptor-α gene with skeletal responsiveness to estrogen in post-menopausal women

Polymorphic genetic markers of estrogen-receptor-alpha (ER alpha) gene studied so far in osteoporosis reside in non-coding region with uncertain functional significance. The purpose of the present study was to search for nucleotides changes in the exon 1 and 5' regulatory region of ER alpha gene, to study the nature of their linkages to the previously reported Pvull polymorphism in intron 1 and their functional significance in postmenopausal osteoporosis. Direct sequencing of exon 1 and promotor region of ER alpha gene revealed a synonymous nucleotide substitution from T to C at position 262, 29 nucleotides downstream from the putative start codon. No nucleotide change was found in the promotor region. Linkage disequilibrium between the T262C polymorphism and the Pvull polymorphism in intron 1 of ER alpha gene was demonstrated in 129 post-menopausal women (p <0.001). After treating 96 post-menopausal with 0.3 mg or 0.625 mg conjugated equine estrogen (CEE) for 2 yr, vertebral bone mineral density (BMD) increased regardless of the T262C genotype. However, with regard to femoral neck BMD, only those subjects that were homozygous for the T262C polymorphism had an increase in femoral BMD (+5.9 +/-1.4%, mean +/- SE; p <0.0001). Using analysis of covariance to assess the effects of the T262C polymorphism, the intronic Pvull polymorphism, doses of CEE and the corresponding baseline BMD on the changes in vertebral or femoral BMD after treatments, it was found that the change in vertebral BMD was related only to the baseline BMD (p <0.05). The change in femoral BMD was independently related to the T262C polymorphism (p <0.01) and the baseline femoral BMD (p <0.01). No effect of the Pvull polymorphism or the doses of CEE on femoral BMD was demonstrated. We concluded that the previously described intronic Pvull polymorphism of ER alpha gene is in linkage disequilibrium with a T262C polymorphism in exon 1. This T262C polymorphism appears to be more directly related to the skeletal response after long-term treatment with estrogen. (C) 2001, Editrice Kurtis.