Identification of a mutation in the human raloxifene response element of the transforming growth factor-beta 3 gene

The human transforming growth factor-beta3 (TGF-beta3) is an important cyto kine to maintain bone mass by inhibiting osteoclast differentiation. Recent ly raloxifene response element (FIRE), a new enhancer with a polypurine seq uence for estrogen receptor (ER)-mediated gene activation, was identified o n the TGF-beta 3gene. Functional analysis of the RRE-mediated pathway has s hown that this would be an important pathway for bone preserving effect. We found a novel mutation in the FIRE sequence by single-strand conformationa l polymorphism analysis in one of 200 Korean women. Cloning and sequencing revealed a heterozygote in which one allele had an insertion of 20 nucleoti des (AGAGAGGGAGAGGGAGA GGG) between nucleotide +71 and +72 and a point muta tion at nucleotide +75 (G-A transition), and the other allele had normal se quence. The insertion was a nearly perfect tandem duplication of the wild t ype DNA sequence. The bone mineral density of the affected woman was not mu ch lower than that of age-matched controls. Transient transfection of the m utant allele showed no significantly different activity compared with that of the wild type allele. These observations suggest that the heterozygote v ariation of the RRE sequence seems not to be operative in determination of bone mass.