title: Sexually dimorphic expression of steroidogenic factor 1 (SF-1) in developing gonads of the American bullfrog, Rana catesbeiana.
abstract: Genetic sex determination leads to gonadal differentiation and ultimately the differences between the sexes in steroid hormone secretion. Gonadal steroidogenesis is critical for the development of a sexually dimorphic phenotype and adult reproductive function. Control of gonadal development and steroidogenesis is under the regulation, at least in part, of steroidogenic factor-1 (SF-1). We have begun to characterize SF-1 expression in an amphibian to determine the role of this protein in development and reproduction. We have detected a putative SF-1 protein from several tissues in the American bullfrog, Rana catesbeiana, that co-migrates with mouse SF-1 on a Western blot. Our results show that bullfrog SF-1 protein is expressed in steroidogenic and other reproductive tissues in a manner similar to that reported for other species, with high expression in the brain, pituitary, gonad, liver, and interrenal, but little or no expression in non-reproductive tissues such as skin and intestine. Using a quantitative Western blot analysis system, we documented changes in SF-1 protein in the gonads of developing tadpoles. Our results indicate that there is sexually dimorphic expression of SF-1 protein that becomes evident at the time of sexual differentiation of the gonads. In males, the expression of SF-1 decreases following testicular formation and in females the expression increases with the formation of ovaries. This is the first study to investigate changes in SF-1 during development at the protein level. The expression is similar to that reported for changes in SF-1 mRNA expression in chickens and alligators, however, opposite to that seen in mammals and turtles. These results indicate that SF-1 may play a pivotal role in development of the reproductive system in amphibians as it does in other vertebrate groups.
authors.affiliation: Department of Physiology, University of Arizona, P.O. Box 5051, Tucson 85724-5051, USA. lpm@u.arizona.edu
authors.forename: Loretta P
authors.initials: LP
authors.lastname: Mayer
authors.forename: Stefanie L
authors.initials: SL
authors.lastname: Overstreet
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Dyer
authors.forename: Catherine R
authors.initials: CR
authors.lastname: Propper
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics*; D005260:Female; D051717:Fushi Tarazu Transcription Factors; D015870:Gene Expression; D018398:Homeodomain Proteins; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D008297:Male; D051379:Mice; D010053:Ovary / Q000737:chemistry* / Q000254:growth & development; D012333:RNA, Messenger / Q000032:analysis; D011892:Rana catesbeiana / Q000254:growth & development; D018160:Receptors, Cytoplasmic and Nuclear; D012727:Sex Characteristics; D012733:Sex Differentiation; D054339:Steroidogenic Factor 1; D013737:Testis / Q000737:chemistry* / Q000254:growth & development; D014018:Tissue Distribution; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C515058:steroidogenic factor 1, mouse