Induction of UO-44 gene expression by tamoxifen in the rat uterus and ovary

A complementary DNA, uterine-ovarian-specific gene 44 (UO-44), has been iso lated from tamoxifen-induced rat uterine complementary DNA library using di fferential display techniques. UO-44 transcripts are found to be abundant i n the uterus and ovary. UO-44 gene expression in the uterus is strictly reg ulated by estrogens, tamoxifen, and GH, whereas the pure antiestrogen ICI 1 82780 is inhibitory. Treatment of ovariectomized rats and hypophysectomized rats with tamoxifen and GH, respectively, resulted in up-regulation of UO- 44 expression in a dose-dependent manner. In situ hybridization revealed th at UO-44 gene expression was restricted to the luminal and glandular epithe lial cells of the uterus and to granulosa cells of medium-size ovarian foll icles. Transfection studies showed that UO-44 was a membrane-associated pro tein. Because estrogens, tamoxifen, and GH are stimulators of uterine lumin al epithelial cell growth in vivo, UO-44 protein may serve as a mediator of the effect of these compounds in inducing epithelial proliferation and dif ferentiation in these tissues.