Involvement of androgen receptor in sex determination in an amphibian species.

Jun Fujii,Yasuki Matsuo,Takashi Hasebe,Koichi Kawakami,Masahisa Nakamura,Mi-Sook Min,Maho Kodama,Atsuko Ishizuya-Oka,Akira Oike,Balasubramanian Senthilkumaran

doi:10.1371/journal.pone.0093655

Jun Fujii, Yasuki Matsuo + Show 8 more

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https://doi.org/10.1371/journal.pone.0093655

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Abstract

In mice and humans, the androgen receptor (AR) gene, located on the X chromosome, is not known to be involved in sex determination. In the Japanese frog Rana rugosa the AR is located on the sex chromosomes (X, Y, Z and W). Phylogenetic analysis shows that the AR on the X chromosome (X-AR) of the Korean R. rugosa is basal and segregates into two clusters: one containing W-AR of Japanese R. rugosa, the other containing Y-AR. AR expression is twice as high in ZZ (male) compared to ZW (female) embryos in which the W-AR is barely expressed. Higher AR-expression may be associated with male sex determination in this species. To examine whether the Z-AR is involved in sex determination in R. rugosa, we produced transgenic (Tg) frogs carrying an exogenous Z-AR. Analysis of ZW Tg frogs revealed development of masculinized gonads or ‘ovotestes’. Expression of CYP17 and Dmrt1, genes known to be activated during normal male gonadal development, were up-regulated in the ZW ovotestis. Testosterone, supplied to the rearing water, completed the female-to-male sex-reversal in the AR-Tg ZW frogs. Here we report that Z-AR is involved in male sex-determination in an amphibian species.

Highlights

Sex is genetically determined in most vertebrates
Based on macroscopic observations we classified the Tg gonads into three categories: Type 1, both right (RG) and left gonads (LG) were approximately 50% smaller than the normal ovary and containing many somatic cells and fewer oocytes (Figs. 2Ba and h); Type 2, both gonads were 25% the size of normal ovaries with fewer oocytes and many somatic cells (Figs. 2Bb and i); Type 3, the RG appeared macroscopically as a testis without any oocytes, while the LG was a normal ovary with many oocytes as well as somatic cells (Figs. 2Bc and j)
The results collectively indicate that androgen receptor (AR)-transgenesis is associated with femaleto-male sex-reversal in R. rugosa, this reversal is incomplete in comparison to wild-type (Wt) testis

Summary

Introduction

Sex is genetically determined in most vertebrates. As in other vertebrate species, heterogametic sex chromosomes in amphibians determine the male (XX/XY) or female (ZZ/ZW) fate [1,2]. The Japanese frog R. rugosa (2n = 26) has two sex-determining systems within one species [3]. Western and central Japan have the XY system, whereas those in northern Japan have the ZW system (Fig. 1A). Frogs living in northern and central Japan have heteromorphic sex chromosomes, whereas those living in eastern and western Japan are homomorphic (Fig. 1A). The ancestral or basal-type sex chromosomes of the Japanese R. rugosa are found in the Korean R. rugosa [4]. A sex-determining gene has not yet been found in R. rugosa

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