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Presence of Sex Steroids and Cytochrome P450 Genes in Amphioxus

Center for Advanced Marine Research, Ocean Research Institute, the University of Tokyo, Tokyo 164-8639, Japan

Address all correspondence and requests for reprints to: Kaoru Kubokawa, Center for Advanced Marine Research, Ocean Research Institute, University of Tokyo, Nakano, Tokyo 164-8639, Japan. E-mail: kubokawa{at}ori.u-tokyo.ac.jp.

The presence of sex steroids and their receptors has been demonstrated in all vertebrate groups from Agnatha to Mammalia but not in invertebrates. In genomic analyses of urochordates, cytochrome P450 (CYP) genes important for biosynthesis of sex steroids are absent. In the present study, we confirmed the presence of estrogen, androgen, and progesterone by using radioimmunoassay in gonads of amphioxus, Branchiostoma belcheri, which is considered to be evolutionarily closer to vertebrates than other invertebrates. Furthermore, CYP genes encoding CYP11A, CYP17, and CYP19 and transcripts for 17ß-hydroxysteroid dehydrogenase were cloned from amphioxus ovaries. Among invertebrates, the presence of hydroxysteroid dehydrogenase enzymes and metabolized steroids was shown in paracytic Taenia and corals. However, CYPs metabolizing sex steroids have not been demonstrated in invertebrates, nor has an attempt been made to consider the entire pathway from cholesterol to estrogen. This study is the first evidence to suggest the presence of CYP enzymes in sex steroid production in invertebrates.

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				M. E. Baker Amphioxus, a Primitive Chordate, Is on Steroids: Evidence for Sex Steroids and Steroidogenic Enzymes Endocrinology, August 1, 2007; 148(8): 3551 - 3553. [Full Text] [PDF]