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Wnt4a Is Indispensable for Genital Duct Elongation but Not for Gonadal Sex Differentiation in the Medaka, Oryzias latipes.

  • Kanamori, Akira1
  • Kitani, Ryota2
  • Oota, Atsuko2
  • Hirano, Koudai2
  • Myosho, Taijun3
  • Kobayashi, Tohru3
  • Kawamura, Kouichi4
  • Kato, Naoyuki5
  • Ansai, Satoshi6, 7, 8
  • Kinoshita, Masato6
  • 1 Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan, [email protected]. , (Japan)
  • 2 Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan. , (Japan)
  • 3 Laboratory of Molecular Reproductive Biology, Institute for Environmental Sciences, University of Shizuoka, Shizuoka 422-8526, Japan. , (Japan)
  • 4 Department of Marine Bioresources, Graduate School of Bioresources, Mie University, Mie 514-8507, Japan. , (Japan)
  • 5 Department of Environmental Science, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan. , (Japan)
  • 6 Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan. , (Japan)
  • 7 Laboratory of Bioresources, National Institute for Basic Biology, Aichi 445-8585, Japan. , (Japan)
  • 8 Graduate School of Life Sciences, Tohoku University, Miyagi 980-8577, Japan. , (Japan)
Published Article
BioOne (Zoological Society of Japan)
Publication Date
Oct 01, 2023
DOI: 10.2108/zs230050
PMID: 37818883


In most vertebrates, the oviducts and sperm ducts are derived from the Müllerian ducts and Wolffian ducts, respectively. However, in teleosts, the genital ducts are formed by the posterior extension of gonads in both sexes. Whether the genital ducts of teleosts are newly evolved organs or variants of Müllerian ducts is an important question for understanding evolutionary mechanisms of morphogenesis. One of the genes essential for Müllerian duct formation in mice is Wnt4, which is expressed in the mesenchyme and induces invagination of the coelomic epithelium and its posterior elongation. Here, we addressed the above question by examining genital duct development in mutants of two Wnt4 genes in the medaka (wnt4a is orthologous to mouse Wnt4, and wnt4b is paralogous). The wnt4b mutants had a short body but were fertile with normal genital ducts. In contrast, both male and female wnt4a mutants had their posterior elongation of the gonads stopped within or just outside the coelom. The mutants retained the posterior parts of ovarian cavities or sperm duct primordia, which are potential target tissues of Wnt4a. The gonads of female scl mutants (unable to synthesize sex steroids) lacked these tissues and did not develop genital ducts. Medaka wnt4a was expressed in the mesenchyme ventral to the genital ducts in both sexes. Taken together, the data strongly suggest that the mouse Müllerian ducts and the medaka genital ducts share homologous developmental processes. Additionally, the wnt4a or wnt4b single mutants and the double mutants did not show sex-reversal, implying that both genes are dispensable for gonadal sex differentiation in the medaka.

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