Platform Session 21. Gonadal Gene Expression
Tuesday, July 26, 2005
2:00 PM–4:00 PM
Location: CCQ 2000A
(167) HIF-1 IS NECESSARY FOR FOLLICULAR MATURATION.
Alam, Hena 1, Flynn, Maxfield1, Maizels, Evelyn1, Park, Youngkyu1, Johnson, Randall2, Hunzicker-Dunn, Mary1, 1 Northwestern University, Chicago, IL2 University of California, San Diego, San Diego, CA
ABSTRACT- FSH drives the maturation of the ovarian follicle by initiating multiple signaling cascades in granulosa cells (GCs) leading to changes in the rates of translation and stability of various proteins in addition to transcription of various genes. We have previously shown that FSH up-regulates the PI3-kinase/AKT/mTOR pathway, a key pathway controlling translation. One target of this pathway is hypoxia-inducible factor (HIF)-1, the regulated monomer of the transcription factor HIF-1. We have also previously shown that FSH induces HIF-1 protein and HIF-1 transcriptional activity in GCs and have identified VEGF, LHR and inhibin- as transcriptional targets of HIF-1 using a dominant negative HIF-1. We now apply a genetic approach to elucidate the role of the transcription factor HIF-1 in FSH-mediated GC differentiation. GCs were isolated from mice containing two alleles of exon 2 of HIF-1a flanked by loxP sites (HIF-1a f+/HIF-1a f+). GCs from HIF-1a f+/HIF-1a f+ mice were treated with an adenoviral construct expressing the bacterial recombinase CRE (AdCRE) allowing us to obtain a population of GCs unable to produce HIF-1. We found that the FSH-mediated up-regulation of microtubule-associated protein 2D was unaffected in AdCRE treated cells relative to those treated with an empty adenovirus (AdE). However, FSH-mediated up-regulation of the peptide hormone inhibin- required HIF-1 and was abolished in GCs treated with AdCRE verus AdE. Finally, we identified one novel target of HIF-1 transcriptional activity in GCs, the PKA regulatory subunit II (RII). FSH-stimulated expression of RII was abolished in AdCRE treated cells. These data indicate that HIF-1 is required as a positive transcriptional regulator for a subset of genes up-regulated during follicular maturation. Future studies will investigate how depletion of HIF-1 affects the maturation of mouse follicles grown in a 3-D alginate culture system.
KEY WORDS: HIF-1, Follicular Maturation, inhibin-, PKA regulatory subunit II