DIVISION OF REPRODUCTIVE BIOLOGY †Publication List〔Original papers〕
Professor (Specially appointed)

NAGAHAMA, Yoshitaka

Postdoctoral Fellows:

Secretary:GUAN, Guijun
SAKAI, Fumie
SHIBATA, Yasushi
NAKAMOTO, Masatoshi
SHIMADA, Yu

Fish exhibit a range of gonadal forms from gonochorism toseveral types of hermaphroditism, thus providing anexcellent animal model to study the molecular mechanismsof sex determination, gonadal sex differentiation andgametogenesis in vertebrates. Our research focuses on (1) theidentification of regulators involved in sex determination,
gonadal sex differentiation, sexual plasticity, andgametogenesis (oocyte maturation and ovulation), and (2) themechanisms of synthesis and action of these regulators.

Molecular mechanisms of sex determination,
gonadal sex differentiation and sex change

We previously identified DMY (DM-domain gene on theY chromosome) as the sex-determining gene of themedaka (Oryzias latipes), the first in non-mammalianvertebrates. Recently, we developed a gene-specifictransgenic RNA interference (RNAi) technology for theanalysis of loss-of-function phenotypes that develop overlong periods of time, and used it to knock down the dmy
gene in genetically male (XY) fish. Knockdown of dmystrongly downregulated the expression of the only othermale-associated genes (gsdf, sox9a2 and dmrt1), andupregulated the expression of female-associated genes(foxl2 and Rspo1) in XY gonads during the early stages ofsexual differentiation. This shift in the gene expression
pattern resulted in a complete male-to-female sex-reversal
with a typical female pattern of secondary sex
characteristics, producing fertile eggs. Importantly, wewere able to continue a trans-generational knockdown
effect on dmy until at least the F3 generation. In order torescue the effect of dmy knockdown, we singularly
injected or co-injected sox9a2 (marked in cyan) and gsdf
(marked with cherry) into olvas vasa-DMY-knockdown
embryos of the F3 generation. Although singular
injections failed to complete suppression of meiosis andproliferative mitosis but co-injection re-established themale phenotype in the XY gonad leading to complete
formation of the testis, producing fertile sperm. Thisconfirms that gsdf and sox9a2 are genes downstream ofdmy which, can regulate the sexual identity of medaka
even in a DMY-independent manner. We conclude that inT., Shibata, Y., Zhou, L.Y., Katsu, Y., Iguchi, T., and• Charkraborty,Nagahama, Y. (2011). Differential expression of three estrogen receptor

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subtype mRNAs in gonads and liver from embryos to adults of themedaka, Oryzias latipes. Mol. Cell. Endocrinol. 333, 47-54.
Charkraborty, T., Katsu, Y., Zhou, L.Y., Miyagawa, S., Nagahama, Y.,
and Iguchi, T. (2011). Estrogen receptors in medaka (Oryzias latipes)
and estrogenic environmental contaminants: An in vitro-in vivo
correlation. J. Steroid Biochem. Mol. Biol. 123, 115-121.
Fernandino, J.I., Popesku, J.T., Paul-Prasanth, B., Xiong, H., Hattori,R.S., Oura, M., Strussmann, C.A., Somoza, G.M., Matsuda, M.,
Nagahama, Y., and Trudeau, V.L. (2011). Analysis of sexually dimorphic
expression of genes at early gonadogenesis of Pejerrey Odontesthes
bonariensis uing a heterologous microarray. Sex. Dev. 5, 89-101.
Mita, M., Yamamoto, K., and Nagahama, Y. (2011). Interaction ofrelaxin-like gonad-stimulating substance with ovarian follicle cells of
the starfish Asterina pectinifera. Zool. Sci. 28, 764-769.
Mita, M., Yamamoto, K., Nakamura, M., and Nagahama, Y. (2011).
Hormonal action of relaxin-like gonad-stimulating substance (GSS) on
starfish ovaries in growing and fully grown states. Gen. Comp.
Endocrinol. 172, 85-89
Ngamniyom, A., Magtoon, W., Nagahama, Y., and Sasayama, Y. (2011).
Expression levels of bone morphogenetic protein 2b in fins of adultJapanese medaka (Oryzias latipes) exposed to sex steroid hormones. J.
Fish. Aquat. Sci. 6, 119-129.
Okubo, K., Takeuchi, A., Chaube, R., Paul-Prasanth, B., Kanda, S.,Oka, Y., and Nagahama, Y. (2011). Sex differences in aromatase gene
expression in the medaka brain. J. Neuroendocrinology 23, 412-423.
Paul-Prasanth, B., Shibata, Y., Horiguchi, R., and Nagahama, Y. (2011).
Exposure to diethylstilbesterol during embryonic and larval stages ofmedaka fish (Oryzias latipes) leads to sex reversal in genetic males andreduced gonad weight in genetic females. Endocrinology 152, 707-717.
Raghuveer, K., Sudhakumari, C.C., Senthilkumaran, B., Kagawa, H.,
Dutta-Gupta, A., and Nagahama, Y. (2011). Gender differences intryptophan hydroxylase-2 mRNA, serotonin, and 5-hydroxytryptophan
levels in the brain of catfish, Clarias gariepinus, during sex
differentiation. Gen. Comp. Endocrinol. 171, 94-104.

〔Review Article〕

N., Nakamoto, M., Shibata, Y., and Nagahama, Y. (2011).
• Shibata,
Endocrine regulation of oogenesis in the medaka, Oryzias latipes. In

Medaka: A Model for Organogenesis, Human Disease and Evolution,
H. Takeda et al. eds. (Springer), pp. 267-283.

medaka dmy directly or indirectly upregulates the male sexdetermining pathway by activating gsdf and sox9a2expression.

†: This laboratory was closed on 31 March, 2011.

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