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This Article Accepted manuscript (PDF) All Versions of this Article: JOE-08-0108v1 198/1/231    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Espey, L. Articles by Richards, J Search for Related Content PubMed PubMed Citation Articles by Espey, L. Articles by Richards, J

L Espey, Department of Biology, Trinity University, San Antonio, United States
R Lopez, Department of Biology, Trinity University, San Antonio, United States
H Kondo, Department of Obstetrics and Gynecology, St. Marianna University School of Medicine, Kawasaki, Japan
B Ishizuka, Department of Obstetrics and Gynecology, St. Marianna University School of Medicine, Kawasaki, Japan
S Yoshioka, Department of Obstetrics and Gynecology, Kyoto University School of Medicine, Kyoto, Japan
S Fujii, Department of Obstetrics and Gynecology, Kyoto University School of Medicine, Kyoto, Japan
S Hampton, Department of Biology, Trinity University, San Antonio, United States
J Richards, Molecular and Cellular Biology, Baylor College of Medicine, Houston, United States

Correspondence: Lawrence Espey, Email: lespey{at}trinity.edu

Abstract

This report assesses the relatively high incidence of expression of paralogs of several pseudogenes within the cascade of expression of functional genes in the rat ovary in response to an ovulation-stimulating dose of gonadotrophin. Immature Wistar rats were primed with 10 IU eCG s.c., and 48 h later the 12-h ovulatory process was initiated by 10 IU hCG s.c. Ovarian RNA was extracted at 0, 2, 4, 8, 12, and 24 h after injecting the animals with hCG. The RNA extracts were used for RT-PCR differential display to detect gene expression in the ovarian tissue. Sequence analyses of differentially expressed cDNAs revealed that approximately 27% (i.e., 22/82 clones) of the transcripts were fragments of paralogs of known pseudogenes. Of the 22 clones reported here, 12 have high sequence similarity to the cytochrome P450 pseudogene Cyp21a1-ps, and 5 had high sequence similarity to both Cyp21a1-ps and to the aldo-keto reductase gene Akr1c6. The remaining 5 clones were paralogs of the endogenous retrovirus SC1 that has heavily infested the rat genome. Northern analyses reveal that peak expression of all 22 paralogs occurs at 4-8 h into the ovulatory process. In situ hybridisation shows that expression of these pseudogenes is primarily in the granulosa layer of ovulatory follicles. In summary, the results reveal that ovarian expression of Cyp21a1-ps-like and SC1-like pseudogenes occurs concurrently with the ovulatory process.