Japanese researchers have discovered a genetic switch called foxl3 that is responsible for determining how germ cells turn out.
Germ cells are cells needed for creating gametes or reproductive cells. They are only found in gonads or organs where gametes are made, such as the testes in males and ovaries in females. Depending on the gonads where gametes come from, they can either be sperm or egg cells. Foxl3, it turns out, is the one that determines what will be produced.
The molecular mechanism that dictates how germ cells turn into sperms or eggs has always been unclear until Toshiya Nishimura and colleagues discovered foxl3 in small fish called medaka (Oryzias latipes).
According to a study published in the journal Science, foxl3 is primarily active in germ cells in females, acting to prevent female germ cells from turning into sperm and allowing the production of egg cells in ovaries. When the researchers deactivated foxl3 in female fish, sperm cells were produced in the ovaries.
Though sperm is normally created in the testes, the sperm produced in the ovaries of female medaka functioned normally, successfully fertilizing eggs and resulting into healthy offspring. Ovary-produced sperm was also easier to obtain, something commercial fisheries would definitely benefit from.
Humans don't have foxl3 in their bodies but the researchers believe that a similar mechanism is at play to determine the production of gametes in people.
Germ cells have always been thought of as passive cells that rely on regulation from other cells so the discovery that it has its own switch mechanism surprised the researchers.
"That this sexual switch present in the germ cells is independent of the body's sex is an entirely new finding," said Nishimura.
Researchers from the National Institute for Basic Biology's Laboratory of Molecular Genetics for Reproduction and the Okazaki Institute for Integrative Bioscience, Kyushu University's Medical Institute of Bioregulation and Department of Advanced Medical Initiatives, the Japan Science and Technology Agency and The Graduate University for Advanced Studies contributed to the study.
Aside from Nishimura, other authors include: Minoru Tanaka, Satoru Kobayashi, Mikita Suyama, Yasuyuki Ohkawa, Ikuko Watakabe, Tasuhiro Yamamoto and Tetsuya Sato.
Photo: Filter Forge | Flickr
