A deletion polymorphism in the RIZ gene, a female sex steroid hormone receptor coactivator, exhibits decreased response to estrogen in vitro and associates with low bone mineral density in young Swedish women

• Low bone mineral density (BMD) is a major risk factor for osteoporotic fracture, and the trait is under genetic control by a large number of genes. It is recognized that estrogen plays an important role in the maintenance of bone mass by binding to estrogen receptor a (ERa). RIZ1 has previously been shown to be a specific ERa coactivator and strongly enhances its function both in vivo and in vitro. We performed in vitro studies comparing the abilities of RIZ1 P704 polymorphic variants (homozygous presence, P704+; absence, P704-; heterozygosity P704+/- of a proline at position 704) to coactivate the ERa and also examined the polymorphism associated to BMD of 343 Swedish women, aged 20-39 yr. The expression vector containing P704- RIZ1 showed an impaired response in coactivating ERa in a ligand- and dose-dependent manner compared with P704+ RIZ (P < 0.0001). The genotype frequencies were 19% (P704+), 32% (P704-), and 49% (P704+/-) and were in Hardy-Weinberg equilibrium. BMD at the heel was higher in the P704+ genotype group than in the P704+/- group (P = 0.02), which was evident also after corrections for fat and lean mass (P = 0.03). We conclude that RIZ1 may be a new candidate gene for involvement in the variation seen in BMD.

Nyckelord

Adult

Bone Density/*genetics

Cohort Studies

DNA-Binding Proteins/*genetics

Estrogen Receptor alpha/*metabolism

Female

Gene Deletion

Genotype

Humans

Nuclear Proteins/*genetics

Polymorphism; Genetic

Random Allocation

Sweden

Transcription Factors/*genetics

MEDICINE

MEDICIN

Publikations- och innehållstyp

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