Codon 325 sequence polymorphism of the estrogen receptor alpha gene and bone mineral density in postmenopausal women

Estrogen receptor alpha (ER alpha) encoding gene is one of the candidate genes to be involved in the development of osteoporosis. Until now correlation between three ER gene polymorphisms (identified with PvuII, XbaI and BstUI) and bone mineral density (BMD) have been investigated. The results of these studies are contradictory. Thus the aim of our work was to search for new, yet unknown, and probably more informative polymorphism(s) of the ER alpha gene. For detection of mutations the whole coding region of the ER alpha gene was screened systematically. In a group of 85 late postmenopausal women all of the eight exons were amplified by polymerase chain reaction (PCR) and fragments were further analyzed by single-stranded conformation polymorphism (SSCP) analysis. Mutations were confirmed by direct DNA sequencing. In the whole coding region of the ER alpha gene two silent mutations in codon 87 and 325, respectively, were found. The silent mutation in codon 85 of exon 1 (GCG-->GCC; A87A) was described previously, as BstUI polymorphism. On the other side, the silent mutation in codon 325 (CCC-->CCG; P325P), located in exon 4, has not been analyzed so far in correlation with BMD. According to the distribution of genotypes CC:CG:GG=49.4:41.2:9.4, we can affirm the existence of genetic polymorphism in codon 325 in our population of late postmenopausal women. The mean femoral neck BMD, but not the lumbar spine BMD, was significantly lower (P=0.029) in the homozygous GG-women with CCG/CCG codon 325 as compared to the homozygous CC-women with the normal codon CCC/CCC. Our results suggest that codon 325 sequence polymorphism of the ER alpha gene might be one of the factors associated with low femoral neck BMD.