Expressional changes of AMH signaling system in the quail testis by photoperiod.

Gonadal sex differentiation proceeds by interplay of various genes including the transcription factors and secretory factors in a complex network. The sex-differentiating genes are expressed not only during early sex differentiation but also throughout the gonadal development, and even in the adult gonads. In addition, the evidence that they actually function in the adult gonads have been accumulated from the studies using the conditional knockout mice. However, many previous studies were focused on one single gene though those genes function in a network. In this study, we for the first time analyzed the expressions of various sex-differentiating genes simultaneously in the adult testis of the Japanese quail (Coturnix japonica), whose testicular functions are dramatically changed by altering photoperiod, to elucidate the roles of them in the adult gonad. We found that anti-Müllerian hormone (AMH) was significantly up-regulated in the regressed testis induced by the short-day condition. The expressions of the transcription factors that promote AMH expression in mammals (SF1, SOX9, WT1, and GATA4) were also increased in the regressed testis. Moreover, AMH receptor (AMHR2) showed the similar expression pattern to its ligand. We also analyzed the expressions of other transforming growth factor beta (TGFB) superfamily members and their receptors. The expressions of the ligands and receptors of TGFB family, and follistatin and betaglycan in addition to inhibin subunits were increased in the regressed testis. These results suggest that AMH is involved in the adult testicular functions of the Japanese quail together with other TGFB superfamily members.