HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend 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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Boerboom, D. Articles by Sirois, J. Search for Related Content PubMed PubMed Citation Articles by Boerboom, D. Articles by Sirois, J. Agricola Articles by Boerboom, D. Articles by Sirois, J.

Equine P450 Cholesterol Side-Chain Cleavage and 3ß-Hydroxysteroid Dehydrogenase/⁵-⁴ Isomerase: Molecular Cloning and Regulation of Their Messenger Ribonucleic Acids in Equine Follicles During the Ovulatory Process¹

^a Centre de Recherche en Reproduction Animale and Département de Biomédecine Vétérinaire, Faculté de Médecine Vétérinaire, Université de Montréal, C.P. 5000, Saint-Hyacinthe, Québec, Canada J2S 7C6

ABSTRACT

The preovulatory LH rise is the physiological trigger of follicular luteinization, a process during which the synthesis of progesterone is markedly increased. To study the control of follicular progesterone biosynthesis in mares, the objectives of this study were to clone and characterize the equine cholesterol side-chain cleavage cytochrome P450 (P450_scc) and 3ß-hydroxysteroid dehydrogenase/⁵-⁴-isomerase (3ß-HSD), and describe the regulation and cellular localization of their transcripts in equine follicles during hCG-induced ovulation. Complementary DNA cloning and primer extension analyses revealed that the equine P450_scc transcript is composed of a 5'-untranslated region (UTR) of 52 nucleotides, an open reading frame (ORF) of 1560 nucleotides, and a 3'-UTR of 225 nucleotides, whereas the equine 3ß-HSD mRNA consists of a 5'-UTR of 61 nucleotides, an ORF of 1119 nucleotides, and a 3'-UTR of 432 nucleotides. The equine P450_scc and 3ß-HSD ORF encode 520 and 373 amino acid proteins, respectively, that are highly conserved (68–79% identity) when compared to homologs of other mammalian species. Northern blot analyses were performed with preovulatory follicles isolated 0, 12, 24, 30, 33, 36, and 39 h post-hCG, and corpora lutea obtained on day 8 of the cycle. Results showed that levels of P450_scc mRNA in follicular wall (theca interna with attached granulosa cells) decreased after hCG treatment (30–39 h versus 0 h post-hCG, P < 0.05), and increased again after ovulation to reach their highest levels in corpora lutea (P < 0.05). Northern blots on isolated cellular preparations revealed that theca interna was the predominant site of P450_scc expression in follicles prior to hCG (P < 0.05). However, transcript levels decreased in theca interna between 30–39 h (P < 0.05) and increased in granulosa cells at 39 h (P < 0.05), making the granulosa cell layer the predominant site of P450_scc expression at the end of the ovulatory process. A different pattern of regulation was observed for 3ß-HSD, as transcript levels remained constant throughout the luteinization process (P > 0.05). Also, in contrast to other species, expression of 3ß-HSD mRNA in equine preovulatory follicles was localized only in granulosa cells and not in theca interna. Thus, this study characterizes for the first time the complete structure of equine P450_scc and 3ß-HSD mRNA and identifies novel patterns of expression and regulation of these transcripts in equine follicles prior to ovulation.

FOOTNOTES

First decision: 25 July 2000.

¹ This study was supported by Natural Sciences and Engineering Research Council of Canada grant OPG0171135. D.B. is supported by a Medical Research Council (MRC) of Canada Doctoral Research Award. J.S. is supported by an MRC of Canada Scientist Award.

² Correspondence. FAX: 450 778 8103; siroisje{at}medvet.umontreal.ca

This article has been cited by other articles:

				T. Mizuta and K. Kubokawa Presence of Sex Steroids and Cytochrome P450 Genes in Amphioxus Endocrinology, August 1, 2007; 148(8): 3554 - 3565. [Abstract] [Full Text] [PDF]

				S. E. London, D. A. Monks, J. Wade, and B. A. Schlinger Widespread Capacity for Steroid Synthesis in the Avian Brain and Song System Endocrinology, December 1, 2006; 147(12): 5975 - 5987. [Abstract] [Full Text] [PDF]

				K. A. Brown, M. Dore, J. G. Lussier, and J. Sirois Human Chorionic Gonadotropin-Dependent Up-Regulation of Genes Responsible for Estrogen Sulfoconjugation and Export in Granulosa Cells of Luteinizing Preovulatory Follicles Endocrinology, September 1, 2006; 147(9): 4222 - 4233. [Abstract] [Full Text] [PDF]

				K A Brown, D Boerboom, N Bouchard, M Dore, J G Lussier, and J Sirois Human chorionic gonadotropin-dependent induction of an equine aldo-keto reductase (AKR1C23) with 20{alpha}-hydroxysteroid dehydrogenase activity during follicular luteinization in vivo. J. Mol. Endocrinol., June 1, 2006; 36(3): 449 - 461. [Abstract] [Full Text] [PDF]

				K. A. Brown, D. Boerboom, N. Bouchard, M. Dore, J. G. Lussier, and J. Sirois Human Chorionic Gonadotropin-Dependent Regulation of 17{beta}-Hydroxysteroid Dehydrogenase Type 4 in Preovulatory Follicles and Its Potential Role in Follicular Luteinization Endocrinology, April 1, 2004; 145(4): 1906 - 1915. [Abstract] [Full Text] [PDF]

				A. E. Stock, N. Bouchard, K. Brown, A. P. Spicer, C. B. Underhill, M. Dore, and J. Sirois Induction of Hyaluronan Synthase 2 by Human Chorionic Gonadotropin in Mural Granulosa Cells of Equine Preovulatory Follicles Endocrinology, November 1, 2002; 143(11): 4375 - 4384. [Abstract] [Full Text] [PDF]