Dax1 suppresses P450arom expression in medaka ovarian follicles

• Published in: Molecular reproduction and development 2007-10, Vol.74 (10), p.1239-1246
• Main Authors: Nakamoto, Masatoshi, Wang, De-Shou, Suzuki, Aya, Matsuda, Masaru, Nagahama, Yoshitaka, Shibata, Naoki
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Aromatase - genetics; Aromatase - metabolism; Biological and medical sciences; Cells, Cultured; Cloning, Molecular; DAX-1 Orphan Nuclear Receptor; Dax1; DNA-Binding Proteins - physiology; Down-Regulation; Embryo, Nonmammalian; estrogen; Female; Forkhead Transcription Factors - genetics; Freshwater; Fundamental and applied biological sciences. Psychology; Gene Expression Profiling; Gene Expression Regulation, Developmental; Gene Expression Regulation, Enzymologic; Homeodomain Proteins - genetics; Humans; Male; medaka; Models, Biological; Molecular Sequence Data; Non mammalian vertebrate reproduction; Oryzias - embryology; Oryzias - genetics; Oryzias latipes; ovarian follicle; Ovarian Follicle - enzymology; Ovarian Follicle - metabolism; P450arom; Receptors, Cytoplasmic and Nuclear - genetics; Receptors, Retinoic Acid - physiology; Repressor Proteins - physiology; Sequence Homology, Amino Acid; Sex Differentiation - genetics; Steroidogenic Factor 1; Transcription Factors - genetics; Vertebrates: reproduction
• ISSN: 1040-452X; 1098-2795
• DOI: 10.1002/mrd.20689

Dax1 is a member of an unusual orphan nuclear receptor family, and is known to regulate P450arom in mammals and is involved in sex differentiation in some vertebrates. To investigate whether Dax1 is involved in the regulation of the steroidogenic pathway for estrogen biosynthesis in medaka ovarian follicles, we isolated Dax1 cDNA from adult medaka ovaries and analyzed its expression pattern in medaka gonads. In adult ovaries, Dax1 mRNA was detected only in postvitellogenic follicles and was not detected in previtellogenic and vitellogenic follicles. In adult testis, Dax1 mRNA was not detected. We compared the expression pattern of Dax1 with that of Foxl2, Ad4BP/Sf‐1, P450c17, and P450arom by in situ hybridization using adjacent sections. In contrast to Dax1 expression, these genes were co‐expressed in vitellogenic follicles but were not detected in postvitellogenic follicles. Thus, in medaka ovarian follicles, Dax1 did not show any overlapping expression patterns against Foxl2, Ad4BP/Sf‐1, P450c17, and P450arom. Moreover, co‐transfection experiments demonstrated that Dax1 inhibits Ad4BP/Sf‐1‐ and Foxl2‐mediated P450arom expression. On the other hand, during early sex differentiation, Dax1 mRNA was not detected in both males and females. Our results suggest that Dax1 down‐regulates Ad4BP/Sf‐1‐ and Foxl2‐mediated P450arom expression in medaka ovarian follicles. Mol. Reprod. Dev. 74: 1239–1246, 2007. © 2007 Wiley‐Liss, Inc.