title: High temperature causes masculinization of genetically female medaka by elevation of cortisol.
abstract: In poikilothermic vertebrates, sex determination is sometimes influenced by environmental factors such as temperature. However, little is known about the molecular mechanisms underlying environmental sex determination. The medaka (Oryzias latipes) is a teleost fish with an XX/XY sex determination system. Recently, it was reported that XX medaka can be sex-reversed into phenotypic males by high water temperature (HT; 32-34 degrees C) treatment during the sex differentiation period. Here we report that cortisol caused female-to-male sex reversal and that metyrapone (an inhibitor of cortisol synthesis) inhibited HT-induced masculinization of XX medaka. HT treatment caused elevation of whole-body levels of cortisol, while metyrapone suppressed the elevation by HT treatment during sexual differentiation. Moreover, cortisol and 33 degrees C treatments inhibited female-type proliferation of germ cells as well as expression of follicle-stimulating hormone receptor (fshr) mRNA in XX medaka during sexual differentiation. These results strongly suggest that HT induces masculinization of XX medaka by elevation of cortisol level, which, in turn, causes suppression of germ cell proliferation and of fshr mRNA expression.
authors.affiliation: Department of Biological Sciences, Graduate School of Science and Technology, Kumamoto University, Kumamoto, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kobira
authors.forename: Toshiya
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Eri
authors.initials: E
authors.lastname: Shiraishi
authors.forename: Takashi
authors.initials: T
authors.lastname: Yazawa
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hirai
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kamei
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kitano
mesh_terms: D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D012734:Disorders of Sex Development; D005260:Female; D006358:Hot Temperature; D006854:Hydrocortisone / Q000378:metabolism* / Q000502:physiology; D008297:Male; D008797:Metyrapone / Q000494:pharmacology; D009990:Oryzias / Q000235:genetics / Q000502:physiology*; D012723:Sex; D019849:Sex Determination Processes; D012733:Sex Differentiation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology; D014960:X Chromosome / Q000378:metabolism
chemical_list: D000963:Antimetabolites; D006854:Hydrocortisone; D008797:Metyrapone