Our focus has been on the development and evolution of secondary sexual characters in fishes. You might be familiar with sexual dimorphism because of the Charles Darwin’s concept “sexual selection”. However molecular basis of sexual characters development and evolution remains largely unclear. To understand the evolutionary basis of biodiversity, we are investigating the mechanisms of the development of sexual characters using medaka, mosquitofish, and swordtail fish as model organisms.

Molecular basis of sexual characters evolution in teleosts

How have the sexual characters diverged? Our analysis revealed that teleost fishes have two functionally distinct Androgen receptor (AR) genes generated by whole genome duplication and subsequently occurred mutation（Ogino et al. Mol Biol Evol. 2016）. Such evolutionary occurrence of two functionally distinct AR proteins might have facilitated the phenotypic diversification of sexual characters in the teleost fishes. To understand the biological importance of the AR gene duplication in the teleost lineage, we are analyzing the functional differences of the AR genes by using the AR mutant medaka.
To understand the evolutionary divergence in morphology of sexual characters, we are investigating how the androgen signaling interacts with developmental pathway and thus how the pathway is related to the molecular evolution of steroid hormone receptors by using teleost fishes showing the prominent sexual characters (Ogino et al. Endocrinology 2014）.

Gene regulatory mechanisms of androgen-dependent sexual characters development

What are the regulating mechanisms of the tissue specificity and the size of sexual characters? We are investigating the mechanism of tissue specific AR gene function by analyzing the histological changes and their relation with chromatin dynamics during the sexual characters development. We also have focused on the reciprocal epithelial–mesenchymal tissue interactions that regulate sexual characters development. Our analyses would contribute to understand the onset mechanism of sexual development disorders and facilitate the generation of the visual reporter transgenic medaka for the rapid detection of EDCs (Sébillot A et al. Environ Sci Technol 2014, collaboration with WatchFrog in France).