We previously reported that the prostaglandin E2 receptor subtype Ptger4b plays a role in ovulation in a teleost species, medaka and that ptger4b mRNA is drastically induced in preovulatory follicles prior to ovulation. The present study focuses on the hormonal regulation of ptger4b mRNA expression using this nonmammalian vertebrate model. Preovulatory follicles that had not been exposed to luteinizing hormone (Lh) in vivo were incubated in vitro with medaka recombinant Lh (rLh), which induced the ptger4b mRNA expression. The addition of trilostane, an inhibitor of 3beta-hydroxysteroid dehydrogenase, strongly inhibited rLh-induced ptger4b expression, and trilostane-suppressed ptger4b expression was restored to the level observed in rLh-treated follicles when 17alpha, 20beta-dihydroxy-4-pregnen-3-one was included in the culture. We determined that the expression of the progestin-activated transcription factor nuclear progestin receptor (Pgr) was also induced by medaka rLh in the follicle and that its expression preceded ptger4b expression. Forskolin treatment induced both pgr and ptger4b mRNA expression in the follicle. Follicular ptger4b mRNA expression was drastically suppressed by RU486, which was demonstrated to compete with 17alpha, 20beta-dihydroxy-4-pregnen-3-one for medaka Pgr in vitro, suggesting a role for Pgr in the expression of ptger4b mRNA. A chromatin immunoprecipitation assay with preovulatory follicles isolated from spawning medaka ovaries demonstrated direct binding of Pgr to the ptger4b promoter. These results indicate that ptger4b expression is regulated by a genomic mechanism involving Pgr.
How to translate text using browser tools
30 April 2014
Luteinizing Hormone-Induced Expression of Ptger4b, a Prostaglandin E2 Receptor Indispensable for Ovulation of the Medaka Oryzias latipes, Is Regulated by a Genomic Mechanism Involving Nuclear Progestin Receptor
Akane Hagiwara,
Katsueki Ogiwara,
Yoshinao Katsu,
Takayuki Takahashi
ACCESS THE FULL ARTICLE
Biology of Reproduction
Vol. 90 • No. 6
June 2014
Vol. 90 • No. 6
June 2014
gonadotropins
ovary
ovulation
steroid hormones/steroid hormone receptors
transcriptional regulation