DNA array analysis of changes in preovulatory gene expression in the rat ovary

During the periovulatory period, the mammalian ovary is the site of dramati c functional and structural changes, leading to oocyte maturation, follicle rupture, and corpus luteum formation. To a large extent, these processes r esult from changes in the transcriptome of various ovarian cell types. To d evelop a broader view of periovulatory changes in gene expression in the ov ary and to identify further genes involved in periovulatory events, we used the recently developed DNA array technology. Immature female eCG-primed ra ts were killed either immediately before or 6 h after ovulation induction w ith hCG. Total ovarian RNA was isolated and used to prepare radiolabeled cD NA probes, which were hybridized to DNA arrays representing approximately 6 00 rat genes. Quantitative analysis identified a multitude of regulated gen e messages, including several genes involved in extracellular matrix degrad ation and lipid/steroid metabolism previously reported to be induced by hCG , This screening also identified a group of candidate genes whose ovarian e xpression and gonadotropin regulation was hitherto unknown. The induction o f three of these genes, encoding cutaneous fatty acid-binding protein, the interleukin-4 receptor alpha chain, and prepronociceptin, was confirmed and further characterized by Northern blot analysis. In addition, in situ hybr idization analysis showed that hCG administration resulted in exclusive or predominant expression of all three genes in theca cells, These results dem onstrate that DNA arrays can be used to identify genes regulated during the periovulatory period, thus contributing to a more detailed understanding o f the molecular mechanisms of ovulation.