Sex determination in the teleost medaka, Oryzias latipes.

Although the sex of most animals is determined by genetic information, sex-determining genes had been identified only in mammals, several flies, and the worm Caenorhabditis elegans until the recent discovery of DMY (DM-domain gene on the Y chromosome) in the sex-determining region on the Y chromosome of the teleost fish medaka, Oryzias latipes. Functional and expression analyses of DMY have shown it to be the master gene for male sex determination in the medaka. The only sex-determining genes found so far in vertebrates are Sry and DMY. Therefore, the medaka is expected to become a good experimental animal for investigating the precise mechanisms involved in primary sex determination in nonmammalian vertebrates. This article reviews the origin of DMY and the sexual development of gonads in the medaka. The putative functions of DMY are also discussed.